ISSN:0003-2654    

DOI:10.1039/AN96691FX009

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

Volume 9 I. No. 1080, Pages I43 - 222 March, 1966THE ANALYSTTHE JOURNAL OF THE SOCIETY FOR ANALYTICAL CHEMISTRYCONTENTSREVIEWThe Analysis for Residues of Chlorinated Insecticides and Acaricides-K. 1. . . . . . . . . . . . . . . . . . . Beynon and K. E. ElgarPAPERSSpectrophotometric Determination of Small Amounts of Antimony i n Lead-J. Bassett and J. C. H. Jones . . . . . . . . . . . . . . . .The Use of Lithium-drifted Germanium Diodes for the y-SpectrometricDetermination of Radioactive Fission-product Nuclides-M. F. Banham, A. J.Fudge and J. H. Howes . . . . . . . . . . . . . . . . . .Determination of Catechol in Cigarette Smoke-J. D. Mold, M. P. Peyton, R. E.Means and T. B. Walker . . . . . . . . . . . . . . . . . .Determination of Zinc i n Trace-element Superphosphate by A.C.Polarography-G. Curthoys and J. R. Simpson . . . . . . . . . . . . . . . .Simultaneous Determination of Iodine and Bromine in Urine by Neutron-activation Analysis-E. P. Belkas and A. G. Souliotis . . . . . . . .SHORT PAPERSMicro Determination of Inorganic Phosphorus in Plasma-B. B. Bauminger andG. Walters . . . . . . . . . . . . . . . . . . . . . .An Improved Iodine Determination Flask for Whole-bottle Titrations-E. J.Green and D. E. Carritt . . . . . . . . . . . . . . . . . .An Automatic, Determination of Thoria i n Thoria - Urania Mixtures-W. A.Stuart . . . . . . . . . . . . . . . . . . . . . . . .A Rapid Method for Determining the Moisture Content of Gelatin and AnimalGlue-R. T. Jones . . . . . . . . .. . . . . . . . . . .A Method for Determining Copper Compounds Present on Leaf Surfaces-R. B. Sharp . . . . . . . . . . . . . . . . . . . . . .REPORT BY THE ANALYTICAL METHODS COMMITTEESpectral Characteristics of Eugenol-Essential Oils Sub-committee . . . . . .COMMU NlCATlONThe Determination of Fluorine by Neutron Activation--]. M. Bakes and P. G. JefferyBook Reviews . . . . . . . . . . . . . . . . . . . . . . . .Errata . . . . . . . . . .PageI43I76I80I89I95I99205207208210212214216217222Summaries of Papers in this Issue. .. . . . . . . . . iv, vi, viiiPrinted and Published for the Society for Analytical Chemistry by W. Heffer & Sons Ltd.. Cambridge, England.Enquiries Communications to be addressed to t h e Editor, J. B. Attrill. 14 Belgrave Square, London, S.W.I.about advertisements should be addressed t o Walter Judd Ltd., 47 Gresham Street, London, E.C.2.Entered as Second Class at New York. U.S.A.. Post Office

ISSN:0003-2654    

DOI:10.1039/AN96691BX011

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

iv SUMMARIES OF PAPERS I N THIS ISSUE [March, 1966Summaries of Papers in this IssueThe Analysis for Residues of Chlorinated Insecticidesand AcaricidesA ReviewSUMMARY OF CONTENTSIntroductionSampling and storageExtraction proceduresSoilsCropsWaterAnimal tissues and productsColumn chromatographyPaper chromtographyThin-layer chromatographyLiquid - liquid partitionPrecipitation of fats and waxesChemical methodsOther miscellaneous methodsGas - liquid chromatographyTotal halide analysisPolarograph yBioassayColorimetric and ultravioletanalysisInfrared analysisFluorimetryClean-up proceduresQuantitative analysisK. I. BEYNON and K. E. ELGARPaper chromatographyThin-layer chromatographyThe positive identification ofpesticide residuesRecommended methodsGeneral proceduresIndividual procedures(i) Aldrin(ii) BHC(iii) Chlorbenside (Mitox)(iv) Chlordane(v) Chlorfenson (Oves)(vi) Chlorobenzilate(vii) DDT, TDE and DDE(viii) Dicofol (Kelthane)(ix) Dieldrin(x) Endosulfan (Thiodan)(xi) Endrin(xii) Heptachlor and its(xiii) Methoxychlor(xiv) Oxythane (Neotran)(xv) Tetradifon (Tedion)(svi) Toxspheneepoxide“Shell” Research Limited, Woodstock Agricultural Research Centre, Sittingbourne,Kent.Analyst, 1966, 91, 143-175.REPRINTS of this Review paper will soon be available from the Secretary, The Societyfor Analytical Chemistry, 14 Belgrave Square, London, S.W.l, a t 5s.per copy, post free.A remittance for the correct amount, made out t o The Society for AnalyticalChemistry, MUST accompany every order; these reprints are not available through TradeAgents.Spectrophotometric Determination of 0.01 to 0.1 per cent.ofAntimony in LeadThe development of a spectrophotometric method for the determinationof small amounts (0.001 to 0.1 per cent.) of antimony in lead is described.The proposed method is based on the extraction of antimony from hydro-chloric acid solution with di-isopropyl ether, followed by spectrophotometricdetermination with the iodide procedure. The presence of other impurityelements usually found in lead causes no significant interference.J. BASSETT and J. C. H. JONESChemistry Department, Woolwich Polytechnic, London, S.E. 18.A ~ , d y s t , 1966, 91, 176-179March, 19661 THE ANALYST VMATERIALS FORELECTROPHORESISWHEREHOWcan I find a comprehensive list of materialsfor any aspect of electrophoresis?A BDH leaflet, 'Materials for Electrophoresis',describes gel media, chemicals forpreparing buffer solutions, stains and indicators,solvents and miscellaneous reagents.are the various methods of zone electrophoresiscarried out?Detailed descriptions illustrated by plates andline drawings are given in a new BDH publication,'Methods in Zone Electrophoresis', by Dr.J. R.Sargent. This immensely practical book dealswith general theory, apparatus, high and lowvoltage electrophoresis, electrophoresis onvarious media, immunoelectrophoresis, etc.Sargent, J. R., 'Methods in Zone Electrophoresis',a BDH publication, 1965, ~ v o ., 107 pp., 8s 6dpost freeThe leaflet on 'Materials for Electrophoresis'may be obtained free from Poole on request.THE BRITISH DRUG HOUSES LTDBDH Laboratory Chemicals DivisionPOOLE DORSETELI vi SUMMARIES OF PAPERS I N T H I S ISSUEThe Use of Lithium-drifted Germanium Diodes for they-Spectrometric Determination of RadioactiveFission-product Nuclides[March, 1966The superiority of a y-spectrometer incorporating a germanium - lithiumdiode detector and field-effect transistor head amplifier over the conventionalsodium iodide - thallium system, for the resolution of most of the difficultdeterminations encountered in fission-product ratliochemistry, is demonstrated.M. F. BANHAM, A. J. FUDGE and J. H. HOWESChemistry and Electronics Divisions, U.I<. Atomic Encrgy Research Establishment,Harwcll, Didcot, Berks.Analyst, 1966, 91, 180-185.Determination of Catechol in Cigarette SmokeA procedure has been devised for the specific determination of catecholin cigarette-smoke condensates. This procedure should also be applicableto the determination of catechol in other materials resulting from pyrolyticor combustion processes.As the catechol is isolated without recourse to the formation of a deriva-tive, no interference is encountered as a result of the presence of guaiacolor similar compounds. Avoidance of the use of alkaline conditions throughoutthe procedure has permitted reproducible and high recoveries.J. D. MOLD, M. P. PEYTON, R. E. MEANS and T.B. WALKERResearch Department, Liggett and Myers Tobacco Company, Durham, NorthCarolina, U.S.A.Analyst, 1966, 91, 189-194.Determination of Zinc in Trace- element Superphosphateby A.C. PolarographyZinc has been effectively determined in “trace-element superphosphate”with an a.c. polarographic technique. This technique is both rapid andaccurate and compares favourably with the atomic-absorption method. Thezinc is maintained in solution by polarographing in an acid electrolyte ofM hydrochloric acid a t a pH of less than 1. The method eliminates the time-consuming process of separation from interfering ions.The presence of the hydrogen reduction wave does not materiallyinterfere with the zinc reduction wave as happens in conventional d.c.polarography .G.CURTHOYS and J. R. SIMPSONNewcastle University College, The University of New South Wales, Australia.Analyst, 1966, 91, 195-198.Simultaneous Determination of Iodine and Bromine in Urineby Neutron- activation AnalysisNeutron-activation analysis was used for the simultaneous determinationof iodine and bromine in urine. The activated iodine and bromine wereseparated by radiochemical methods. The 0.46 MeV and 0.55 MeV peakareas of 1281 and 82Rr, respectively, were measured by means of a multi-channel analyser. The amounts of iodine and bromine were found to beof the order of lo-’ and g ml-l of urine, respectively, for normal humanbeings of different ages.E. P. BELKAS and A. G. SOULIOTISChemistry Department, Nuclear Research Centre “Democritus,” Athens, Greece.Analyst, 1966, 91, 199-204...Vlll SUMMARIES OF PAPERS I N THIS ISSUEMicro Determination of Inorganic Phosphorus in Plasma[March, 1966Short PaperB.B. BAUMINGER and G. WALTERSChemical Pathology Department, New Cross Hospital, Wolverhampton.Analyst, 1966, 91, 205-206.An Improved Iodine Determination Flask for Whole-bottleTitrationsShort PapevE. J. GREEN and D. E. CARRITTDepartment of Geology and Geophysics, Massachusetts Institute of Technology,Cambridge, Massachusetts, U.S.A.Analyst, 1966, 91 , 207-208.An Automatic Determination of Thoria in Thoria - UraniaMixturesShovt PaperW. A. STUARTU. K. Atomic Energy Research Establishment, Hsrwell, Didcot, Berks.Analyst, 1966, 91, 208-210.A Rapid Method for Determining the Moisture Content ofGelatin and Animal GlueShort PaperR. T. JONESThe Gelatine and Glue Research Association, Warwick Street, Birmingham 12.Analyst, 1966, 91, 210-212.A Simplified Method for Determining Copper CompoundsPresent on Leaf SamplesShort PaperR. B. SHARPInstrumentation Department, Kational Institute of Agricultural Engineering,Wrest Park, Silsoe, Bedfordshire.Analyst, 1966, 91, 212-213.Spectral Characteristics of EugenolReport prepared by the Essential Oils Sub-committeeANALYTICAL METHODS COMMITTEE14 Belgrave Square, London, S.W.1.Analyst, 1966, 91, 214-215

ISSN:0003-2654    

DOI:10.1039/AN96691FP049

出版商:RSC    

年代:1966

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN96691BP059

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

MARCH, 1966 THE ANALYST Vol. 91, No. 1080 The Analysis for Residues of Chlorinated Insecticides and Acaricides A Review* BY K. I. BEYNON AND K. E. ELGAR (44Shell” Research Limited, Woodstock Agricultural Research Centre, Sittingbourne, Kent) SUMMARY OF CONTENTS Introduction Sampling and storage Extraction procedures Soils Crops Water Animal tissues and products Column chromatography Paper chromtography Thin-layer chromatography Liquid - liquid partition Precipitation of fats and waxes Chemical methods Other miscellaneous methods Gas - liquid chromatography Total halide analysis Polarograph y Bioassay Colorimetric and ultraviolet analysis Infrared analysis Fluorimetry Clean-up procedures Quantitative analysis Paper chromtography Thin-layer chromatography The positive identification of pesticide residues Recommended methods General procedures Individual procedures (i) Aldrin (ii) BHC (iii) Chlorbenside (Mitox) (iv) Chlordane (v) Chlorfenson (Ovex) (vi) Chlorobenzilate (vii) DDT, TDE and DDE (viii) Dicofol (Kelthane) (ix) Dieldrin (x) Endosulfan (Thiodan) (xi) Endrin (xii) Heptachlor and its epoxide (xiii) Methoxychlor (xiv) Oxythane (Neotran) (xv) Tetradifon (Tedion) (xvi) Toxaphene WE have attempted to prepare a selective and critical review of the work published up to May, 1965, on the analysis for residues of the most widely used chlorinated insecticides and acaricides, and their principal metabolites.We have made no attempt to present an historical account of previous work, but have attempted to produce a balanced picture of procedures that are relevant at the present time and also to give our own assessment of their relative j m port ance .A comprehensive treatise edited by Zweigl was published during 1963 and 1964 on the analysis of pesticides. The second volume of this work gave detailed accounts of procedures for the analysis of most of the compounds considered in this review. However, few of the methods recommended then can be recommended today as being the best procedures available for chlorinated pesticides. Residue analysis procedures, particularly for chlorinated pesticides, were revolutionised in 1961 by the application of gas - liquid chromatography (GLC) with either electron-capture or microcoulometric detection systems. The analysis of small amounts of pesticide is possible with such procedures, and the detection of 0.05ng of some compounds with the electron- capture detector is now routine.In the absence of a valid control sample, GLC analysis cannot provide positive identification of a particular pesticide when only one retention-time value is obtained. Many naturally occurring products respond to GLC detectors and can be mistaken for pesticides, and often such naturaI products are not completely removed by the clean-up procedures that are used. This * Reprints of this paper will be available shortly. For details see Summaries in advertisement pages. 143 However, a few words of caution are necessary.144 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF [AfldySt, VOl. 91 behaviour is encountered also with analytical procedures other than GLC.It is a factor, however, that has been ignored by many workers.. The problem of the positive identification of a residue in a sample of unknown history is the most important one facing the residue analyst at the present time and it will be discussed in detail in a later section. We have considered many aspects of the analysis for residues of chlorinated insecticides and acaricides, and the review will be of use to those chemists who wish to analyse samples of unknown history, as well as to those who wish to analyse samples from field trials where adequate controls are available and where the sample history is known. SAMPLING AND STORAGE The principles to be adopted when sampling crops and soils for the analysis for residues of chlorinated pesticides are the same as those when sampling for residues of other compounds.Correct sampling, however, is so important that the principles cannot be emphasised too strongly. Experimental studies of sampling procedures for crops have been reported by Huddleston et L z Z . , ~ Van Middelem et aL3 and by Poos et u Z . ~ Lykken et ~ ~ 1 . ~ 3 ~ have reviewed the literature on the sampling of crops and the second of these reviews,6 in particular, presents a clear account of the correct procedure. Lykken6 recom- mends that the gross samples of crops should be 25 to 100 lb or units, and that this sample should be mixed, quartered and sub-divided to obtain representative replicate 2-lb samples for analysis. The size of the gross sample, however, must be related to the size of the plot and to the size of the crop.Studies of the procedures for soil sampling do not seem to have been reported, but the recommendations concerning the representative nature and size of the sample for crops apply also to soils. Soil samples are generally taken as a core and Lichtenstein et a1.' took 30 cores (2 inch diameter x 9 inches deep) from 500 square feet of dieldrin-treated soil. The depth to which sampling takes place will depend on the depth of penetration of the pesticide. These chlorinated insecticides and their derivatives are strongly adsorbed on all arable soils and do not leach through the soil to any significant extent. I t is usual, therefore, to sample within the cultivated depth unless the total amount or depth variation of the residues is required.The statistical principles of sampling have been summarised by Garber.8 The need for the sample to be representative of the plot from which it is taken6 and the necessity for the participation of the residue chemist in samplingg cannot be emphasised too strongly. These needs are so great that it is surprising that more experimental work has not been reported on the comparison of sampling procedures for residue analysis, especially for soils. STORAGE OF SAMPLES Crop and soil samples must be stored at a temperature at which the residues and the crop do not decompose further whilst awaiting extraction. This may seem an obvious precaution but experimental evidence for such stability is rarely given in the literature. Samples are often stored6 at 1" to 5" C, but this temperature is too high for the extended storage of many crops.Although most of the chlorinated pesticides considered here may be stable for some days when stored at 1" to 5" C, it is recommended that storage for longer than a few days should be at temperatures of -10" C, or below, in closed containers. Whatever the storage temperature, the pesticide residues in the crop and soil must be shown experi- mentally to be stable under the conditions used. Such evidence is best obtained by analysing field-treated samples after storage for different times at different temperatures. It is advisable to record the weight of samples with a high water content prior to deep-freeze storage, for when they regain room temperature disintegration and moisture loss can be rapid.The extracts of crops and soils must also be stored, prior to analysis, in conditions under which further decomposition of the pesticide does not occur, and storage at 1" C, or below, and in the absence of light is recommended. If recovery experiments are carried out at the time of the extraction it is possible to obtain evidence for the stability of the pesticide during the storage of the extract. EXTRACTION PROCEDURES A universal extraction procedure has not yet been developed and the problems peculiar to the extraction of chlorinated pesticides from soils, crops, water, animal tissues and fatty materials, respectively, will be considered.March, 19661 CHLORINATED INSECTICIDES AND ACARICIDES 145 Often, insufficient evidence is given for the adequacy of an extraction procedure, par- ticularly for soils.Most workers carry out recovery experiments by introducing known amounts of pesticide at the extraction stage. However, whilst good recoveries are sufficient evidence that the subsequent stages of the analytical procedure (e.g. , concentration steps, clean-up) do not lead to losses of pesticide, they do not necessarily mean that the extraction procedure is efficient. I t is far more difficult to remove a pesticide from field-treated samples, when the pesticide has penetrated into the sample structure, than to extract a pesticide introduced at the blending stage. The efficiency of an extraction procedure may be estab- lished by extracting field-treated samples with a range of solvents for a range of extraction times.When increasing the severity of the extraction conditions (solvent polarity or extrac- tion time) leads to no further increase in the amount of pesticide extracted, one can be reasonably satisfied that the procedure is adequate. SOILS Many chlorinated pesticides are strongly bound by dry soils, and the adsorptive capacity of the soil will vary considerably with moisture content , organic-matter content, the polarity of the compound and other factors. For example, hexane will extract aldrin from dry soil, but it is not suitable for the extraction of dieldrin residues.10 Extraction with acetone will give a good recovery of most chlorinated pesticides but the co-extracted material can interfere with the analysis. Gouldenll has shown that acetone extraction of soils followed by partition of the pesticide into hexane is a satisfactory procedure when the final analysis is by electron- capture GLC.The use of 10 per cent. acetone in hexane is considered to be adequate for the removal of most chlorinated pesticides from soil without excessive co-extraction of inter- fering substances.1° Benzene - TPA,12 hexane - IPA13 and pentane - acetone13 have also been used. Soxhlet extraction of the air-dried soil with acetone has been used for the removal of DDT from soill4 but air-drying, prior to extraction, cannot be recommended as a general procedure as the pesticide may be volatile. A procedure that can be applied to the extraction of chlorinated insecticides from a range of soil types has been described.15 The soil is mixed with anhydrous sodium sulphate to make it friable and is then extracted with 10 per cent.acetone in hexane in an end-over-end tumbler for 1 hour. In order to improve recoveries for a wide range of chlorinated pesticides the acetone content of the extraction solvent can be increased to 20 per cent. without undue interference, especially if the final analysis is to be by GLC. CROPS Surface rinsing of crops is simple and results in little interference from co-extractives. I t is, however, inadequate for the removal of residues other than those adhering loosely to the crop surface or dissolved in the waxy, surface layer. Since it is rarely used nowadays, we will confine our attention to the extraction of the whole crop. The extraction of pesticides from crops has been reviewed by Bann,lo Heinisch,ls Thornburg17 and Van Middelem.ls Useful comparisons of extraction procedures have been described by Bann,lo Klein and his c o - w o r k e r ~ ~ ~ ~ ~ ~ ~ ~ ~ and by Hardin and Sarten.22 Mills, Onley and Gaither23 have described a useful acetonitrile extraction procedure applicable to many chlorinated pesticides in a range of crops.Prior to the extraction, the crop should be subdivided and mixed thoroughly. Grains such as rice, and seeds such as cotton are broken in a mill prior to the e ~ t r a c t i 0 n . l ~ BannlO showed that aldrin and dieldrin were readily extracted from a range of fresh, un- processed crops such as alfalfa, carrots, corn, dates, figs, beans, turnips and wheat by macera- tion with hexane followed by tumbling.With many crops, especially frozen or canned foods, low recoveries or emulsion problems were encountered. To overcome these problems the use of a mixture of polar and non-polar solvents or the maceration of the crop with solvent in the presence of sodium sulphate has been recommended. The water-miscible solvent is generally removed by water washing prior to analysis. Klein and his co-workers20y21 compared the efficiencies of three procedures for the extraction of DDT, aldrin and methoxychlor from spinach, collards and beans. Blending with benzene - IPA was more efficient than either tumbling with benzene - IPA or Soxhlet extraction with benzene or benzene - IPA. Satis- factory recoveries (95 per cent.) were obtained by blending the crop and IPA (in the ratio of 1 g to 1 ml) for 2 minutes followed by the addition of benzene (2 ml) to the mixture and a further 2 minutes maceration.Complete equilibrium existed between insecticide and sample blend, and two pour-offs were necessary to achieve 95 per cent. recovery.146 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF [Analyst, VOl. 91 Hardin and Sarten22 compared the efficiencies of different extraction procedures for the removal of DDT from field-treated collards and their results are summarised in Table I. Blending with IPA followed by the addition of hexane and further blending was the most efficient and rapid procedure, as was found by Klein and his co-workers.19@~21 TABLE I THE EXTRACTION OF DDT FROM COLLARDS DDT extracted (p.p.m.) Extraction procedure (mean values) Tumbling with hexane (30 minutes) .. .. .. .. . . .. 20.9 4 1*1* Blending IPA (2 minutes), addition of hexane + tumbIing (30 minutes) Blending with hexane (2 minutes) + tumbling (30 minutes) . . . . . . Blending IPA (2 minutes) + addition of hexane + further blending (2 minutes) . . . . . . . . .. .. . . .. . . 35.9 f 2-9 Grinding sodium sulphate + tumbling hexane (30 minutes) . . .. .. 24-8 i 1.0 30.4 & 2.6 . . 36.4 5 1.1 *Standard deviation Whilst a procedure suitable for the extraction from a wide range of crops of most of the chlorinated pesticides considered here has not been developed, some general indications are possible. Blending for some minutes with hexane - IPA, benzene - IPA (or with ethanol or acetone instead of IPA) should be suitable procedures.The presence of anhydrous sodium sulphate during the blending should further decrease the emulsification problems. It does not seem to have been established clearly that prior blending with the water- miscible solvent is necessary, and a simple blending procedure with the mixed-solvent system is an efficient procedure for many pesticides.1° 9 1 7 WATER The analysis of pesticides in water has been reviewed recently by Hindin, May and D u n ~ t a n . ~ ~ Chlorinated insecticides are of low solubility in water and they may be extracted with water-immiscible solvents, such as hexane or benzene. However, when it is necessary to extract large volumes of water to achieve the necessary sensitivity, batchwise procedures can be time consuming. Rosen and M i d d l e t ~ n ~ ~ removed the pesticides from 2000 litres of water with a carbon filter, and desorbed them from the carbon by Soxhlet extraction with chloroform.Recoveries of BHC, chlordane, DDT, aldrin, TDE and endrin were in the range 75 to 86 per cent. a t the 2-5 p.p.m. level, but some were lower below the 1 p.p.m. level. Teasley and Cox2s preferred a batchwise liquid - liquid extraction process as they considered that several chlorinated pesticides were unstable on activated carbon. Subse- quently Kahn and Wayman27 described a simple apparatus that can be used for the continuous extract of several hundred litres of water with petroleum spirit, and they obtained a 83 to 100 per cent. recovery at the 0.2 to 340 p.p.b. (parts per thousand million) level with a range of compounds.Previous workers have extracted large volumes of water in order to detect chlorinated pesticides at the p.p.b. level. However, because of the high sensitivity of gas -liquid chromatography, it should now be possible to carry out liquid - liquid extraction by a smaller batchwise process prior to analysis by GLC. ANIMAL TISSUES AND PRODUCTS The chlorinated compounds dealt with in this review and many of their metabolites are fat soluble, and some of them tend to concentrate in the lipoid portion of the plant or animal system. Extracts of fatty materials can have such a large amount of co-extracted material that analysis by the usual residue methods is impossible without rigorous clean-up. Extraction merely involves dissolving the product in a suitable solvent before the necessary clean-up procedures are begun. However, attempts have been made to minimise the fat content of the extract, e.g., by the use of polar-extracting solvents, such as acetonitrile17 or dimethyl s~lphoxide,28~~~ or by the use of an aqueous mixture containing an em~lsifier.~~ However, the solubility of fat in these solvents is low and some of the pesticide may remain in the undissolved fat.Extraction with alcoholic alkali is useful for the alkali-stable cyclodiene insecticide^,^^ 932 and also for DDT and its analogues,= although DDT is unstable to alkali.March, 19661 CHLORINATED INSECTICIDES AND ACARICIDES 147 A general procedure for the preparation and extraction of dairy products has been given by Mills.34 Butter was clarified by warming to about 50" C and filtered.Cheese and milk were blended with sodium (or potassium) oxalate and alcohol, extracted with three volumes of ether and light petroleum, and the combined non-aqueous layers washed with water and evaporated. The fat obtained from all these products was dissolved in light petroleum. The procedure used for milk has been improved by O n l e ~ 3 ~ with an ether - acetonitrile - dioxane mixture as extracting solvent that gave a cleaner extract more quickly. A useful general scheme for extracting dairy products has been given by Langlois et aZ.36 that could also apply to all fatty tissues. A sample containing not more than 1 g of butter fat was ground with 25 to 30 g of Florisil (containing 5 per cent. of water) to give a free-flowing powder.This mixture was placed on top of 25 g of clean pre-washed Florisil in a chromatographic column, and the whole column was eluted with 20 per cent. volume of methylene chloride in light petroleum. Up to 650ml of eluant removed DDT, DDE, lindane and heptachlor and the more polar heptachlor epoxide, dieldrin and endrin with good recovery and precision. Other published methods for animal fats and tissues have usually involved grinding with anhydrous sodium ~ u l p h a t e ~ ~ ,38 939 ?40 or sand41 and dissolution in a suitable solvent. CLEAN-UP PROCEDURES Column chromatography remains the most widely used method of clean-up and its general use is likely to continue for some time. Many other procedures are useful, however, for particular problems. When GLC was first introduced for the analysis of residues of chlorinated pesticides it was hoped that clean-up would no longer be necessary.This is true for many samples of known history when residues of 0.1 p.p.m., or higher, are present. However, when it is necessary to detect residues a t a level less than 0.05 p.p.m., clean-up is generally necessary. For analysis by GLC with electron-capture detection or with the newer version of the micro- coulometer, the clean-up may take place on a smaller scale than was necessary with the older colorimetric procedures. Clean-up is almost always essential with samples of unknown history unless no interference is obtained at the desired level of sensitivity without clean-up. Gas - liquid chromatography has been used successfully for the clean-up of extracts and this application is covered in other sections.COLUMN CHROMATOGRAPHY The convenience and resolving power of column chromatography make it the most commonly used method of clean-up. Despite much work on the theory of chromatography, selection of particular solid or liquid phases is still largely empirical. Any separation may be due to the simultaneous action of adsorption, partition and ion-exchange processes, but as one of these factors usually predominates, they will be considered separately. ADSORPTION CHROMATOGRAPHY- The adsorptive capacity of a material depends on such factors as its structure, method of preparation, the presence of impurities, the treatment or activation it may have undergone, particle size, moisture content and the eluting solvent. I'ariation in the sorptive properties between different batches of many adsorbents tends to be high, and many workers have preferred to work with those with reasonably reproducible properties, such as the synthetic magnesium trisilicate, Florisil, A wide range of materials has been evaluated, however, and Florisil, alumina, silica gel and carbon are commonly used.Evaluations of Florisil by M ~ d d e s ~ ~ and by RiIills and c o - w o r k e r ~ , ~ ~ ~ ~ ~ of silica gel by Moats,43 and of carbon by Coulson and Barnes,44 Cassil et aZ.,45 1 B a e t ~ ~ ~ and have been reported. Coulson4* has advocated the use of aluminium silicate, while cellulose,49 magnesiaz3 931 and clays of the at tapulgite type have also been ~ s e d . ~ 1 The more powerfully the pesticide is sorbed to the adsorbent, the more polar the solvent needed to desorb and elute it from the column.Table IT gives the adsorbents in order of increasing adsorptivity and the eluting solvents in order of increasing polarity. In practice, hexane or benzene is the usual solvent with, if necessary, the addition of a small proportion of ether or acetone to remove the more polar pesticides, The adsorbents may be activated or de-activated as desired by the removal or addition of water. The mechanism of adsorption by charcoal differs from that of the adsorbents in Table 11. Generally, pesticides containing aromatic groups are more strongly adsorbed on charcoal than are the cyclodiene pesticides.148 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF TABLE I1 ADSORPTIVITY OF ADSORBENTS AND POLARITY OF SOLVENTS [Analyst, Vol.91 Adsorbents Cellulose Kieselguhr (Celite) Magnesia Silica gel Magnesium trisilicate Alumina Clays Solvents Hexane C yclo hexane Benzene Methylene chloride Ether Ethyl acetate Acetone Alcohols PARTITION CHROMATOGRAPHY- The partition of chlorinated pesticides into polar solvents from less polar solvents is exploited in partition chromatography, particularly for separations from fats and waxes. Abdallah and Landheerso have used both acetonitrile and dimethylformamide supported on Celite in the clean-up of lindane and DDT from fat by using pentane or hexane as eluant. Hoskins et aLsl successfully used alumina coated with polyethylene for the clean-up of a variety of crops with 40 to 65 per cent. of aqueous acetonitrile as eluant, and achieved an average pesticide recovery of 88 per cent.Thornburgl’ has suggested this method as a “universal” type of clean-up. Coulson et aZ.,52 Zweig et aLs3 and Crosby and LawsM have successfully used gas - liquid chromatography as a method of clean-up. This quite simple technique could have wider application to the stable chlorinated materials. ION-EXCHANGE CHROMATOGRAPHY- Ion exchange has proved useful in clean-ups5 956 and metabolism studiess7 of pesticides, but has been used to only a limited extent with chlorinated compounds. Few members of the group considered here are sufficiently acidic or basic for the technique to be employed, although it has been used for the analysis of DDA in ~rine.~8 PAPER CHROMATOGRAPHY Paper chromatography has been used extensively for the separation of mixtures of pesticides in extracts of plants, animal tissues and dairy products.I t has been used widely for the identification and quantitative analysis of pesticides, but has been little used for the clean-up of extracts prior to analysis by other methods. For this reason a more detailed discussion of paper chromatography will be considered later in the “Quantitative Analysis’’ section. The principles outlined in that section apply also when paper chromatography is used for clean-up. If paper chromatography is to be used for clean-up, a marker spot should be made visible and the assay sample must be eluted from the relevant section of the paper prior to further analysis. Any solvent which produces an RF value of 0.95 or greater for the desired component is satisfactory for the elution.However, the stationary and mobile phases may also be eluted along with the spot and may interfere in the subsequent analysis; this and the slowness of the method and the low capacity of the paper are the reasons why paper chromato- graphy has been used mainly for the identification of pesticides and not for clean-up. Recently Heinisch and Neuberts9 have described the application of wedged-shaped paper strips for the clean-up of plant extracts. TH I N-LAYER CHROMATOGRAPHY Thin-layer chromatography (TLC) may be used for the clean-up of extracts prior to analysis by other methods, for the qualitative analysis of pesticides, and for their direct quantitative analysis. TLC is more rapid and has a higher capacity than paper chromatography, and is more useful for the clean-up of extracts.TLC generally gives sharper resolution of chlorinated pesticides than paper chromatography and, unlike the latter, can be carried out successfully without the impregnation of the adsorbent with a stationary phase. The adsorbents, developing systems and detection systems will be considered in detail in the section on quantitative analysis. When TLC is used for clean-up prior to analysis by other methods, the pesticide is desorbed from the adsorbent at the R, value corresponding to the desired pesticide. TheMarch, 19661 CHLORINATED INSECTICIDES AND ACARICIDES 149 RF value is determined by running a marker spot alongside the extract and only the marker spot is made visible.The correct solvent must be chosen for removal of the separated components from the adsorbent. Little specific information has been given as to a suitable solvent, but of course, any solvent which gives an RF value of 0.95 or greater for the particular component is suitable. Acetone, ether, alcohol or mixtures of these with hexane should remove most of the pesticides considered here. Abbott and Thornsons* have suggested wedge-layers for clean-up by TLC and this system should be useful for chlorinated pesticides. Taylor and Fishwickel have used loose-layer chromatography on alumina with hexane for the separation of aldrin, DDT and its metabolites, BHC, heptachlor epoxide, endrin and dieldrin, and this technique is especially useful for the investigation of solvent systems for the separation of pesticides by column chromatography.LIQUID - LIQUID PARTITION Jones and Riddick62 extracted several pesticides including methoxychlor, chlordane, lindane and DDT with hexane from plants, animal tissues and dairy products. The pesticides were partitioned into acetonitrile, and considerably less interference was encountered in the subsequent colorimetric or polarographic analysis as a result. This liquid - liquid partition procedure has now been used widely, especially for extracts of animal fats and tissues, and its use has been extended to many pesticides and a wide range of solvent pairs are available. Burchfield and Storrse3 showed that lindane, DDT and aldrin partition from hexane into DMF to a greater extent than into acetonitrile, and that the use of the high-boiling DMF was no drawback as the pesticide may be recovered from this solvent readily by dilution with water followed by partition back into hexane.The use of DMSO - hexane and acetonitrile - hexane was compared by Haenni et aLe4 who showed that BHC, aldrin, dieldrin, endrin and heptachlor partitioned to a greater extent into DMSO than into acetonitrile. Extraction of crops and soils with acetone and subsequent dilution of the extract with aqueous sodium sulphate solution and partition into hexane was used successfully by Goodwin et aLe5 This sytem was used also for animal tissues66 but it was found to be unsuitable for animal fats.# The animal fats and dairy products were extracted with hexane, and the pesticides (aldrin, dieldrin, $$’-TDE, $$’-DDT, BHC and heptachlor) partitioned into DMF.The DMF was diluted with water and the pesticide was partitioned back into hexane prior to analysis by GLC. Recoveries from partition processes are generally good, even at the microgram or nano- gram level, as long as the mixing of the solvent phases is effective and the partition is repeated a sufficient number of times.40 The relative volumes of solvents and the number of times that partitioning must be repeated may be determined from the partition coefficients, and TABLE 111 PARTITION COEFFICIENTS6’ OF CHLORINATED PESTICIDES AT 25.5” c Partition coefficient Pesticide Aldrin . . .. . . y-Chlordane . . . . pp’-DDE . . . . oo’-DDT . . , . &b’-DDT . . . . Dieldrin . . .. Endosulfan I . . . . Endosulfan I1 . . Endrin . . . . Heptachlor . . . . Heptachlor epoxide . . Lindane . . .. TDE .. .. .. Telodrin . . . . 7 Hexane - acetonitrile 0-73 0.40 0.56 0.45 0.38 0.33 0.39 0.13 0.35 0.55 0.29 0.12 0.17 0.48 Hexane - 90 per cent. aqueous dimethyl sulphoxide 0.89 0.45 0.73 0.53 0-40 0.45 0.55 0.09 0.52 0.77 0.35 0.09 0.08 0.65 Iso-octane - 85 per cent. aqueous dimethyl formamide 0.86 0.48 0.65 0.42 0.36 0.46 0-52 0.14 0.5 1 0.73 0.39 0.14 0.15 0.63 Iso-octane - dimethyl formamide 0.38 0.14 0.16 0.10 0.08 0.12 0.16 0-06 0.15 0.2 1 0.10 0.05 0.04 0.17 Iso-octane - dimethyl formamide (with 125 mg butter extractive) 0.39 0.16 0.18 0.11 0.09 0.13 0.17 0-07 0.16 0.23 0.1 1 0.06 0.04 0.19150 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF [Analyst, VOl.91 several lists of values are a ~ a i l a b l e . * 0 ~ ~ ~ ~ 6 ~ ~ ~ 7 It is generally found that co-extractives do not have any great effect on the partition of the pesticide.67 Beroza and Bowman67 have measured the partition coefficients of a range of pesticides (Table 111) and have shown that liquid - liquid partition can be useful not only for clean-up, but for more positive identification of the pesticides. The extract can be analysed before and after a suitable partition procedure. This will enable the partition coefficient of the component to be determined, and comparison of the results with the values in Table I11 will allow more positive identification. This procedure is rapid and is useful during GLC when the particular conditions will not resolve a given pair of insecticides, and may often be quicker than attempting to alter the GLC conditions in order to attain the desired resolution.More recently these workers68 have extended their work and have used a counter-current distri- bution system to clean-up extracts and also to identify pesticides. PRECIPITATION OF FATS AND WAXES Precipitation procedures have often been used to remove interfering waxes and fats. Fairing and W a r r i n g t ~ n ~ ~ cooled acetone solutions of plant and animal tissues to -15" C to precipitate fats and waxes, which were then removed by filtration, and they reported good recoveries of methoxychlor from apple wax. Williams70 obtained good recoveries of chlordane when the interfering waxes in tomatoes, cabbages and apples were precipitated by cooling a methanolic solution in an ice-bath.Precipitation procedures have been used extensively by McKinley, McCully and their c o - ~ o r k e r s . ~ ~ , ~ ~ 9 7 2 9 i 3 3 7 4 3 7 5 Good recoveries of DDT ( o f and @'), TDE (Rhothane), methoxychlor and dicofol were obtained71 when waxes were precipitated at -70" C from acetone extracts of a range of fruits and vegetables. DDE, DDT and TDE were recovered from a range of animal fats72 when acetone solutions were cooled and a three-stage cooling procedure, one at 5" C and two at -70" C, was necessary to precipitate the fat from large samples. Recently a simple apparatus has been d e s ~ r i b e d ~ ~ ~ ' ~ for the precipitation of fats and waxes which should be useful for the processing of large numbers of samples.With the apparatus benzene - acetone solutions of plant and crop extracts were cooled to -70" C, and good recoveries were obtained by DDT (op' and $@'), lindane, heptachlor, aldrin, heptachlor epoxide, endrin and methoxychlor. Gunther and Blinn76 cooled benzene extracts of avocados to 0" C to crystallise the benzene together with any DDT. The avocado oil was removed from the crystal mush by filtration. McKinley and S a ~ a r y ~ ~ deposited an extract of butter fat on a charcoal column and eluted dieldrin without the butter fat with acetone at -70" C. The precipitation procedure is good for the removal of fats and waxes but not particularly useful for the removal of interference from other sources. Chromatographic procedures will usually remove several of the interfering classes of compounds and have found more widespread application.GLC procedures are sometimes less prone to direct interference from fats and waxes than many of the older colorimetric methods. However, the removal of fats and waxes that do not cause direct interference during G1.C is desirable if extended GLC column life with maintained efficiency is required. Precipitation procedures have also been used in other ways. C H E M I c AL M ETH o D s Chemical methods of removing or modifying co-extracted material can be applied to a limited range of pesticides but are tending to be superseded for normal use by partition and adsorption methods. However, the modification of a pesticide by chemical reaction will probably find wider use as an aid to identification.TREaTMENT WITH ALKALI- Saponification has been widely used as a method of clean-up for the alkali-stable cyclodiene compounds, aldrin,31 dieldrin32 977 and end~-in,~* for DDT (with conversion to DL>E)33Y79 for lindane,s0381 heptachlor epoxides2 and methoxychlor (with conversion to the ethylene compound) .83 A quicker method of clean-up with alkali has been reported for endrin by Albert,84 in which a potassium hydroxide - Celite column was used instead of saponification. One layer of potassium hydroxide - Celite (14 to 17 per cent. water in the mixture) was placed between two layers of magnesium oxide - Celite and the column eluted with light petroleum.March, 19661 CHLORINATED INSECTICIDES AND ACARICIDES 151 TREATMENT WITH ACID- Schechter et aZ.g5 cleaned up chloroform extracts of milk containing DDT and glycerides by hydrolysis with fuming sulphuric acid.Davidow86 improved the method by percolating the extract through a column containing concentrated and fuming sulphuric acid supported on Celite. This technique has also been used for lindane.87 TREATMENT WITH OXIDISING AGENTS- This technique has occasionally been used for pesticides resistant to oxidation such as DDT, dieldrin and lindane as in the method of Gunther et aLa8 for the rapid determination of DT>T in dairy products, and that of O'Donnell et for dieldrin in unsaponifiable materials. Alkaline potassium permanganate has been the most favoured reagent, but chromic acid, acid or alkaline peroxide and acid chromic anhydride may also find a p p l i c a t i ~ n .~ ~ OTHER MISCELLANEOUS METHODS STEAM DISTILLATION- Some of the chlorinated pesticides are steam-volatile, but little attempt has been made to use this property because the volatility is greatly reduced in the presence of crop and particularly tissue extracts. have hydrolysed chlorfenson with alkali and steam distilled the resulting p-chlorophenol, and Gunther and Blinng2 have described a similar procedure for oxythane. Ott and GuntherS3 have attempted to devise a general method for fat clean-up by using forced volatilisation. The method is rapid and recoveries are good except for TDE and methoxychlor. HYDROLYSIS WITH ENZYMES- Cliffordg4 showed that clean-up by using enzymes was effective, but the method is lengthy and the enzyme not readily available so that this observation has not been used to any great extent.Gunther and J eppsongO and Butzler et QUANTITATIVE ANALYSIS Methods that have been used for the quantitative analysis of chlorinated pesticides In will be discussed in turn, and in each the specificity of the procedure will be considered. the last sub-section the specificity of residue methods will be considered in detail. GAS - LIQUID CHROMATOGRAPHY The rapid application of GLC as a technique and in particular the development of selective methods of detection for halogenated compounds have led to its world-wide use in the residue analysis of chlorinated pesticides. Because of the sensitivity and selectivity that it can offer, GLC has become the preferred method for the whole group of compounds con- sidered here.It was once hoped that the relatively small response from most crop constituents would mean little or no clean-up of but because of the interest in much lower residue levels, this hope has not been realised. Nevertheless, GLC has many of the charac- teristics of an ideal residue method. The high sensitivity of the detectors has meant that only small weights of pesticide, and thus smaller weights of co-extracted materials, are injected and this has led to the use of lower loadings of stationary phases and lower column temperatures, which have given more efficiency, resolution and life to GLC columns. NON-SELECTIVE DETECTION SYSTEMS- The first work on the gas chromatography of insecticides in 1958 was carried out by using thermal-conductivity detection.98 Later workers have also used this d e t e c t ~ r , ~ ~ , ~ ~ but the sensitivity is poor and it lacks selectivity.This latter disadvantage also applies to the use of the flame-ionisation detector despite its much greater sensitivity. SELECTIVE-DETECTION SYSTEMS- MiwocouZomet yy- Coulson et a1.9'3 introduced the rnicrocoulometric titrating system as a GLC-detection device in 1960. The method involves combustion of the vapours eluted from the gas chromato- graph and automatic titration of the hydrogen chloride (or sulphur dioxide) produced, and152 BEYNON AND ELGAR: ANALYSIS FOR RESIDVES OF [.Analyst, Vol. 91 it has been reviewed by CassilS9 and by Challacombe and Mch'ulty.lo0 Its usefulness in residue analysis has been assessed by Burke and Johnsonlol and more recently by Burke and Hols- wade.lo2 They conclude that optimum conditions for the analysis of over a hundred chlorine- or sulphur-containing pesticides are a 6-feet x 4.5-mm i.d.aluminium column, packed with 10 per cent. DC 200 silicone fluid coated on an 80 to 90 mesh Celite support, previously acid and base-washed and silanised. This column is conditioned and is operated at 210" C with nitrogen as carrier gas at a flow rate of 120 ml per minute. The maximum sensitivity of the original microcoulometer (Model R-100) is about 0.1 pg chloride, the range to about 1 mg chloride and precision &3 to 5 per cent. The detector has the great advantage of internal standardisation, the silver ions being electrically generated, For a limit of detection of 0.01 p.p.m.of pesticide, the extract of 10 g or more of crop must be injected onto the chromatograph, and thus for reasonable GLC column life extensive clean-up of extracts is required. In addition, the solvent and any materials emerging from the GLC column before the pesticide are usually vented to the atmosphere to prevent in- complete combustion and fouling of the electrodes. To minimise decomposition of pesticide at the high column temperature that is used, CassilS9 recommended the use of a quartz insert in the injection block. The instrument proved immediately popular, particularly in the U.S.A., being put to use not only for analysis of crop residues103~104y105,106 but also for a great deal of environmental monitoring work.24 9 1 ° 7 ,lo* A modified design (Model K-200) has a sensitivity about ten times better than the original.An ultimate sensitivity of about 10 ng of chloride is claimed for this later instrument, a great improvement. The increased sensitivity makes lower column loadings and lower temperatures feasible, which will decrease the tendency for decomposition of some pesticides. E1ectrol.L capture- The quantitative GLC analysis of halogenated compounds with high electron affinity was found to be difficult with some ionisation detectors because of combination of these molecules with electrons. This disadvantage was exploited by Lovelock and Lipskylog for the selective detection of such molecules. In this detection system the eluted vapour passes into an ionisation cell containing two electrodes.The cathode is in contact with a source of electrons which is usually a few hundred millicuries of tritium. The anode collects the electrons accelerated by a d.c. or pulsed potential, and this produces a standing current of 10-9 to Vapours entering the cell capture electrons to a greater or lesser extent and thus diminish the standing current. This change of current is measured. The decrease in current which is normally found is exponentially related to the number of vapour molecules. The working range extends to about 30 per cent. of the standing current, about the first 5 per cent. being rectilinear, the dynamic range being rather less than a thousand. The sensitivity of the detector varies with the electron affinity of the compound, which itself varies not only with the functional group but also with its molecular environment.l1° The measurement of the electron affinities of many compounds has revealed an interesting correlation with biological activity.lll ,ll2 v113 The potentialities of the high sensitivity of the detector for the quantitative analysis of traces of polychlorinated insecticides were quickly seen and applied65 9959979114 and the purely qualitative aspect has received less attention.The device has drawbacks, such as the lack of specificity for halogen, the differing sensitivity among even the halogenated materials and the need for frequent calibration. However, despite these drawbacks, with ordinary care in ~ p e r a t i o n l l ~ j ~ ~ ~ the detector has been a great success. For halogenated pesticides it offers a sensitivity greater than a thousand times that of the microcoulometer, and high selectivity.The characteristics and performance of the detector have been reviewed by L o ~ e l o c k , ~ ~ ~ Landowne and Lipsky,l16 Dimick and Hartmannll' and Clark,l13 and have been shown to be only slightly affected by minor changes in flow rate and detector temperature. For a residue level of 0-01 p.p.m. the extract from only milligram amounts of samples needs to be injected, and although clean-up is necessary at this level, it can be carried out rapidly and conveniently with small volumes of extract, adsorbent and partitioning solvent. Goodwin et aZ.65 described a procedure for the analysis to a concentration of 0-1 p.p.m. of a variety of chlorinated insecticides with a commercial detector, and showed that increased sensitivity could be obtained with one made to a design by Lovelock.llo Both planar or radial geometry of the radioactive source have since been used, with little apparent difference amp.March, 19661 CHLORINATED INSECTICIDES AND ACARICIDES 153 in performance.The detector has been used many times for the analysis of chlorinated pesticides in crops, soils and animal tissues and products, and optimum conditions have been reviewed recently by Burke and Giuff rida.l18 These workers recommend as operating conditions a 6-feet x 4-mm glass column packed with 10 per cent. DC 200 silicone oil (12,500 cS) on 80 to 90 mesh, acid and base-washed and silanised kieselguhr. This column and the detector are maintained at 200" C and 120 ml per minute of nitrogen is passed through.These conditions do not permit the chromatography of endrin without decom- position.G5 Halogen leak detector- This device was first used as a GTX detector by Cremer et a1.120 for the chlorinated solvents, and was extended to residues of the chlorinated pesticides by Goulden et a1.lz1 It consists of two concentric platinum cylinders that act as electrodes. The inner anode is sensitised by treatment with alkali and is indirectly heated to about 800" C and maintained at 250 volts d.c. relative to the cathode, which receives a standing current of positive ions. The presence of halogen in a vapour passing through the cell induces an increase in this current, which can be amplified (if necessary) and recorded in the usual way.The system has, at the moment, the disadvantage of poor stability. Improvements in design will, it is hoped, eliminate or at least reduce this defect. However, it has the great merit of excellent selectivity for halogen, and about 10 ng can be detected in a simple circuit without amplification, and less than 1 ng in a more elaborate circuit. With these advantages it may well have a promising future. Other selective detectors- Beilstein jlame detector-The Reilstein test has been adapted for use as a quantitative GLC d e t e c t ~ r . ~ ~ " l ~ ~ All or part of the effluent from the GLC column is led through a copper thimble held in the hot zone of a Bunsen burner and an intense green flame (Amax. =473 mp) indicates the presence of halogen.The sensitivity by visual observation is in the microgram range for halogen, but this can be increased by the use of instruments. Quantitatively, the time of appearance and disappearance of the coloration can be related to the response from another detector such as a katharometer, coupled prior to the flame or in parallel with it. Solzrtion-cozzdztctivity dete~tor-Sternbergl~~ has made use of the properties of combusted vapours to devise a selective detector. The gases emerging from the GLC column, after combustion, contact a flowing film of distilled water. Any soluble, ionised components produce a change in the electrical conductivity. The claims for sensitivity (6 x 10-9 g for DDT, with signal equivalent to twice the noise level), selectivity (lindane is 4000 times more sensitive than hexane) , and repeatability are g00d.l~~ 91zGy127 Although both of these detectors have involved careful development of ingenious ideas, it would seem that the other selective devices previously mentioned have more immediate promise, and these two will probably not be refined for general use.COLUMN AND INJECTION BLOCK MATERIALS- In its early days GLC was primarily used by workers in the petroleum industry with much emphasis on the high-temperature separation of the inert hydrocarbons, and on this account the problem of decomposition of more thermally labile compounds has sometimes been overlooked. Exposure to hot metal surfaces or carbonised deposits in the injection block can bring about decomposition of many pesticides such as DDT,12* dicofol129 and particularly e n d ~ - i n .~ ~ 91199128 The composition of the column tubing also plays a part in decomposition. Beckmann and BevenuelZ8 compared four materials and found increasing recovery of the insecticide injected with columns of copper, stainless steel, aluminium and quartz, respectively. Dimick and Hartmann117 have shown that Pyrex glass is as effective as quartz. Cassilg9 has overcome decomposition in the injection block by using a quartz liner to the block, and borosilicate glass may be substituted for ~ l u a r t z . l l ~ J ~ ~ I t is becoming normal practice in analysing thermally unstable compounds such as pesticides to dispense with an injection block and to inject directly on to the GLC column in order to avoid decomposition at this point.154 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF [A?Zd$St, VOl.91 SOLID SUPPORTS- Although capillary columns have been used for analysis of pesticides131 their evaluation for residue analysis has so far proved di~appointing.~~~ In an attempt to use the high efficiencies of capillary columns to secure more positive identification, the drawback of low column capacity proved insuperable, The extreme dilution of pesticides in residue extracts means that the stream-splitting normally used with capillaries is impracticable. Wider-bore capillaries with their higher capacity may improve this picture, but it is doubtful if a resolution superior to that of packed columns can be obtained in a reasonable time. With packed columns the optimum column bore would appear to be 3 to 4 mm (0.125 t c 0.160 inches), and for best column efficiency the particle-size range of the support material should be narrow (a 10 or 20 mesh fraction). Kieselguhr in its various grades has remained the most popular material, being inert, having a high ratio of surface area to volume anc with reasonable mechanical strength.Recently, a harder and less adsorptive supporl specially developed for GLC (Chromosorb G) has been introduced. Glass micro beadsG5 haw been found to offer no advantage. Low loadings of stationary phases must be used and thc packing of the column can be difficult. The lack of porosity of glass beads can lead to higf back pressures. For the compounds under review the most important property of a support materia is the absence of any tendency to cause decomposition.Goodwin et aL.65 located the mail source of decomposition in the support material and showed that nanogram quantities o endrin could be chromatographed successfully by using small amounts of a polar stationar: phase (Epikote resin 1001) in admixture with the non-polar phase to act as an active-sit suppressor. The proportion of resin used (10 per cent. of the silicone) was insufficient tl modify the resolution of the pesticide mixture given by the silicone. The same worker later found that other epoxy additives could be used132 and that pre-treatment of the suppor by refluxing with epichlorhydrin gave chromatography without decomposition when silicon alone was used as stationary phase. This approach has also been used by Gunther et aL1: TABLE IV RELATIVE RETENTION TIMES OF CHLORINATED PESTICIDES~~~ Pesticide Lindane .... .. I-Eeptachlor . . .. Dicofol . . .. .. Aldrin* . . .. .. op’-TDE olefin . . .. Heptachlor epoxide . . Chlorbenside . . .. pp’-TDE olefin . . .. y-Chlordane . . .. @’-DDE .. .. Endosulfan . . .. Chlorfenson . . . . p-Chlordane . . .. pp’-DDA methyl ester . . pp’-DDE.. .. . . Dieldrin . . .. . . op’-TDE . . .. .. Endrin . . .. .. Chlorobenzilate . . .. Pp’-TDE .. .. op’-DDT.. . . pp:-Methoxychlor olefin * p p -DDT . . .. pp’-Methoxychlor . . Tetradifon . . . . Chlordane . . .. Toxaphene .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. * . .. .. . . .. .. .. .. .. .. .. .. .. .. .. .. .. Relative retention time 0.52 o*s1 0.99, 3.82 1.00 1.12 1-20 1.35 1.34 1.35 1.37 1.44, 1-91 1.46 1-46 1-48 1-69 1-72 1-72 1.90, 2.09 2-07 2.12 2.2 1 2.52 2-70 3.90 4-29 0.52, 0.66, 0.74, 0.82 0.06, 1.14, 1.36, 1.50, 2-3 1.29, 1.45, 1.55, 1.87, 2-17 2.45, 2-85, 3.36, 4.03, 4.52 * Aldrin retention time 5.5 minutes.Column of 10 per cent. DC 200. Carrier-gas flow rate: 120 ml per minute.21 Major peaks are in italics. Temperature of 210’ C.March, 19661 CHLORINATED INSECTICIDES AND ACARICIDES 155 who used tris-(2-biphenylyl)phosphate (Dow K-1110) as a stabiliser, but Beckman and Bevenue128 have reported that this is not always successful. The adsorptivity of the support material has also been reduced by acid and alkali washing, and active hydroxyl groups have been eliminated by conversion to their trimethylsilyl derivatives with hexamethyldisilazane.lo2 t118 STATIONARY PHASES- The stationary phase is selected for the separation it offers of compounds actually or potentially present in the mixture to be analysed.Experience to date has shown that a separation involving the use of silicone compounds based essentially on differences in vapour pressure gives the best resolution of the chlorinated group of pesticides. Work with the dimethyl siloxane polymers DC 200,100~102~118 SE 30,135 SF 96,13e Dow 111179137 and E 301659130 and with the almost non-polar methylphenyl siloxane polymer DC 710138 has been published and tables of retention times have been given by C a ~ s i l , ~ ~ Bevenue,138 Burke and Holswade102 and Burke and Giuffrida.lls The relative retention times of the compounds under review on a non-polar phase are given in Table IV.From this table it can be seen that on the silicone phase there are pairs of compounds difficult to resolve, notably $$'-DDE and dieldrin, $$'-TDE and o$'-DDT, aldrin and dicofol, endosulfan and chlorfenson, heptachlor epoxide and chlorbenside. Other stationary phases with greater polarity have been chosen for the ability to separate these pairs and also to resolve a pesticide from a peak suspected of being due to a co-extracted natural product. Apiezon hydrocarbon greases,130 9139 the silicone polymers modified with fluorine-containing groups38*140 or with nitrile groups (GE XE 60132 and XF 1112132), epoxy resins,65 polyesters141 and the Sonidet P40139 have been used to give this extra resolution with chlorinated insecti- cides, but Ucon and other esters143 91459146 have been used for other pesticides.TEMPERATURE- Excessively high column temperatures lead to decomposition and loss of resolution. The original work with pesticide^^^^^^ was carried out at about 250" C, but the advent of more sensitive detectors has meant, among other advantages, that lower operating tempera- tures can be used and 200" to 210" C has recently been recommended.102~118 Goodwin et al.65 have shown that temperatures as low as 160" C give better chromatography with reasonable retention times with a lower percentage of stationary phase (2.5 per cent.) with 0.25 per cent. of epoxy resin added to prevent decomposition on the uncoated support.To give efficient vaporisation and to prevent condensation the injection block (if used) and the detector must be at a temperature at least as high as that of the column, but it is not necessary for them to be much hotter. Burke147 has evaluated temperature programming for the analysis of chlorinated pesticides, and has shown that a complex mixture of compounds with a range of vapour pressures could be conveniently separated, but the procedure did not achieve separations that were not possible with isothermal operation. Electron-capture detectors containing tritium as the source of radiation cannot be operated at temperatures above 200" C.148 9149 MEASUREMENT IN GLC ANALYSIS- The microcoulometer gives an absolute measure of the weight of compound eluted and burnt, but with other detecting systems the amount of pesticide that each peak represents may be found by calibration with an internal standard, but preferably with an external standard.The peak area or peak height may be measured, although the measurement of the former generally gives more reproducible results150 except for peaks of short retention time. IDENTIFICATION- In the absence of valid untreated control material a single retention time obtained by GLC is not sufficient evidence for the positive identification of a compound. Many naturally occurring products can respond to the GLC detectors used for residue analysis. Although the relative response to electron-capture detectors of these naturally occurring co-extractives will generally be much lower than that of the chlorinated pesticides, they are often present 9143 the polyglycol amide Versamid 90OLa :- n m*-rrh h i m h f i v r-nmr-nmtrqt;nn156 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF [A?dySt, Vol.91 There are several methods available of improving the specificity of GLC. Columns with better resolution may help132 and retention times on two or more stationary phases of different type offer additional, though not conclusive, evidence.139 The several-column, single-detector chromatograph produces a characteristic “spectrum” from a single injection and is useful for fairly simple p r ~ b l e m s , l ~ ~ J ~ l but is difficult to interpret for more complex mixtures. Alternatively, information on the identity of a compound may be given by comparison of the responses of the compound to different selective detectors, and this has been successfully demonstrated by Goulden et aZ.121 with the electron-capture and the halogen-leak detectors.Conversion into characteristic derivatives prior to GLC has been exploited by several groups of workers for specific pesticides. Klein et aZ.152 converted DDT and TDE to their ethylene derivatives with alkali, and Beckman and Berkenk~tterl~~ used reduction with sodium in liquid ammonia. Conversion on the nanogram scale can be carried out readily and pre-columns filled with suitable reagents have been used by many workers.154J55~15G~157 9158 Such methods seem capable of offering conclusive evidence of structure. The use of GLC in combination with other procedures is considered later in this section.TOTAL HALIDE ANALYSIS Analysis of pesticide residues by total halide has been thoroughly reviewed in Volume I of the treatise edited by 2weig.l Wet, dry and oxygen-flask combustion and various types of sodium reduction followed by colorimetric or electrometric end-point determination were discussed. Details of the sodium - diphenyl reduction have been given in Volume 2 of the same text, and Grou and Balif159 have used sodamide in paraffin oil for dehalogenation. By present standards the limit of detectability of this method is low, (microgram amounts of halide) ; it is impossible without prior treatment to distinguish between the components of a mixture, and few workers in recent years have concentrated on it. This latter point also applies to neutron activation, another total-halide technique, reviewed by SchmittlG0 and Guinn and Schmitt .lG1 In addition, the sensitivity for chlorine is not particularly high, about 0.1 pg for the 37Cl (n,y) 38Cl reaction, but rather better for bromine, 0.005 pg for the 79Kr (n,y) soBr reaction.This could be a powerful method where many similar samples need to be analysed, but the disadvantages of non-specificity and lack of availability do not encourage its development. PCLAROGRAPHY Polarography has not been used extensively for the analysis of chlorinated pesticides because the method has not the sensitivity of several of the alternative procedures, and also because extensive clean-up of plant and soil extracts is required before analysis by this method. Furthermore, several of the chlorinated pesticides are not reduced during polaro- graphy.The procedure is likely to find more application for the analysis of organo-phosphorus compounds rather than for chlorinated pesticides. The method has been investigated, however, for application to chlorinated pesticides as it is capable of quantitative analysis and also the measurement of the half-wave potentials of the reducible components confers a degree of specificity. Polarography is extremely sensitive for the analysis of reversibly-reducible inorganic Components but the sensitivity is poorer for the analysis of irreversibly-reduced organic compounds. For organic compounds pulse-wave polarography is the most sensitive form of this procedure. Gajan,lG2 R t - a ~ e e ’ ~ ~ and Gajan and Link164 have reviewed the applica- tion of polarography to pesticide analysis.DDT and its metabolites can be determined by p01arographyl~~J~~ and tetramethyl ammonium bromide in aqueous acetone has been used as the base solution167 to determine concentrations of 5 pg per ml. Analysis of DDT by polarography has also been reported by other w ~ r k e r s . ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ I t has been reported170 that the alkyl chlorine atoms of DDT are reduced more easily than the aromatic chlorine atoms. Polarography of DDT after nitration has been reported by Davidek and Janicek.171 The polarography of dieldrin has been described by S w a n e p ~ e l , ~ ~ ~ and K ~ s m a t y i l ~ ~ ha5 used polarography for the analysis of residues of DDT, y-BHC and heptachlor in crops and soils after chromatography.Kosmatyi and Shlyapak174 have determined residues of DDT in a range of crops with a limit of detectability of 2.1 x Other references to the polarography of these compounds and to methoxychlor are given by Gajan and Link.lG4 M (about 7 pg per ml).March, 19661 CHLORINATED INSECTICIDES AND ACA4RICIDES 157 BIOASSAY The use of bioassay for the determination of pesticide residues, including residues of chlorinated pesticides, has been reviewed within recent years by Needham,175 Dewey,l76 Sun1" and P h i 1 l i ~ s . l ~ ~ Most of the work that was reported up to 1962 is considered, and many references are given to the application of bioassay in the determination of residues of chlorinated pesticides. Bioassay has been used extensively because it is capable of detecting very small amounts of toxicants.Only the simplest apparatus and a ready supply of test organisms are required. A wide range of test organisms has been used, including vinegar flies (Drosophila melano- gastev) ,175 9 1 7 6 9 1 7 7 9 1 7 8 house flies (Mzisca domestzca) ,175 9 1 7 6 3 1 7 ' 3178 adult and larval mosquitoes ( A edes, A izopheles and Czdex) ,1i5J76 7177 J~~ alfalfa weevil larvae (HjPera postica) ,lS9 brine shrimps (Artemia s a l i m ) ,177 water fleas (Daphnia m a p a ) ,177 niicrocrustacea (Gammarzzs laczistris) ,l80 guppies (Lebistes reticzdatus) ,175 J~~ 3177 ?li8 and goldfish (Carassizis aztratzis) .177 Uavidow and Sabatinol*l and Dewey and Parkerls2 have described a system for the mass rearing of L>a$/ztzia magna for bioassay, and Geroltls3 has described methods for the breeding of Drosoplzila melawgaster for bioassay.Satisfactory methods have also been des- cribed for house flies and mosquito larvae and are given by Needham.175 Of these test organisms the vinegar fly, house fly and mosquito larvae have been used most extensively. All three species are easy to rear and are sensitive to toxicants. Sun177 has made a useful summary of the susceptibility of several test species to chlorinated insecticides and, although DrosoPhila melattogastev are the most versatile, the choice of test organism will often depend on the pesticide to be assayed and on the possible contaminants. The three basic techniques generally used are (i) direct methods in which the material containing the pesticide is fed directly to the test organism, (ii) film methods in which a film of pesticide is deposited on a surface by evaporation of an extract of the sample followed by exposure of the test organism to the film and (G) aqueous methods where the sample extract is transferred to water that contains the test organism, such as fish or larvae.The direct-feeding method is less sensitive than the other methods but it is quicker and is useful when toxicant levels are high. The results in Table 1' indicate that whilst the aqueous methods can be used to detect pesticides in very dilute solutions the absolute sensitivity in micrograms is not as good as that of the dry-film method. In using these procedures it is important that the test conditions should be standardised and the follou~ing factors must be considered.Naturally occurring compounds can be toxic or can have a masking effect and clean-up is often necessary to achieve the highest sensitivity. Mosquito larvae are particularly sensitive to co-extractives. The susceptibility of a test organ- ism will vary with the age and sex of the species, for example, male Drosophila melanogaster are more susceptible to toxicants than females, and the susceptibility generally decreases as the age increases. Henneberry et aZ.18' have described a simple method in which a rising air stream is used to separate the male Drosophila melaiiogaster from the females. The presence or absence of food during the bioassay can also affect the susceptibility.188.189 Apart from these biological factors, physical factors such as the number of test animals, the size of the container, the time of exposure, temperature, humidity and illumination should be st andardised.The mortality obtained with the assay sample is compared with that obtained by using standard amounts of pesticide. Several methods of calculating the results are described by Sun177; a plot of percentage of mortality on a probit scale and amount of pesticide on a logarithmic scale is generally rectilinear and can be used within the range of 20 to 80 per cent. mortality. The susceptibilities of some test organisms by using the three basic procedures are sum- marised in Table V. The values are not from the same source since a direct comparison of all the basic procedures has not been made. The susceptibilities are generally low in the presence of plant extracts due to masking.The masking effect of a different combination of crops and toxicant has been discussed in detail by Phillips.178 When toxicants other than the compound to be assayed are absent, the results of bioassay agree well with the results obtained by chemical or physical methods.176 9178 Bioassay is extremely useful in parallel screening as the comparison of the results of bioassay with those of specific methods may indicate the presence of other toxic components that may be metabolites of the parent compound. Bioassay results and the results of other158 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF [AnU&Si!, VOl. 91 non-specific methods may be used in combination to provide added confirmation of the presence of a toxicant.However, the use of bioassay has declined during recent years because of its lack of specificity and also because of the difficulties, in comparison with some other procedures, of obtaining reproducibility. Aldrin .. Dieldrin . . BHC . . . . Chlordane . . Endosulphan Endrin . . Heptachlor . . Toxaphene . . Chlorobenzilate DDT . . .. TDE . . . . Rlethox ychlor y-BHC . . TABLE V THE SUSCEPTIBILITIES OF TEST SPECIES TO TOXICANTS Dry-film method LD,, values* (pg per container) .. .. 0.05 .. .. 0.05 .. .. 1.0 .. . . 0.10 .. .. 0.20 .. .. 0.27 .. . . 0.30 . . . . 0.30 . . . . 10 . . . . 32 .. . . 15 .. . . 1s . . . . 500 Direct feeding? per cent. Aqueous solution: mortality for given LC50 dosage in p.p.m. (P.P*m.1 0.2 p.p.m. 89% 0.0088 0.5 p.p.m. 64% - 0.2 p.p.m. 98% 0.017 - - - - - - 0.5 p.p.m. 54% 0.017 0.1 p.p.m. 55% - 10 p.p.m. 2076 - - - 2.0 p.p.m. 0% 0.035 - - 5-0 p.p.m. 0% - * Ref. 184. t Ref. 185. $ Ref. 186. 25 x 200-mm tubes, 24 hours exposure of twenty, 7 to 31-hour old Drosophzla Twenty grams of macerated potato containing pesticide were exposed to Twenty-five 4th instar larvae of Culex p . quinquefasciatus in 100 nil of water melanogaster to pesticide in the absence of plant extracts. 50 one-day old Drosophzla melanogaster for 24 hours. exposed for 24 hours to the pesticide in the absencc of plant extracts. Several attempts have been made to improve the specificity of bioassay. Methods involving a combination of chemical and physical clean-up have been used.lgl Also, the comparison of the response of several different test-organisms to the toxicant can be used to fingerprint the ~ e s t i c i d e .l ~ ~ 7 ~ ~ ~ Other methods of achieving specificity by clean-up, by comparison of the ratio of photomigration, by comparison of rates of mortality, and by the use of several different test-species, have been summarised by Sun,177 Dewey176 and Needham.175 Although bioassay is useful in parallel screening procedures and for the confirmation of results of other methods, its use cannot be recommended as the sole procedure to be adopted for the measurement of residues of chlorinated pesticides. COLORIMETRIC AND ULTRAVIOLET-SPECTROMETRIC ANALYSIS Colorimetry, with ultraviolet or visible radiation, has been until recent years the main source of specific residue methods. Sensitivities of a few micrograms and reasonable specificity have been attained for the whole group of pesticides under review, and a full discussion and details for thirteen of the group are given in volume 2 of the text edited by Zweig.l The need for lower levels of measurement and increasing emphasis on the analysis of metabolic products are being met by progress in other methods with much higher intrinsic selectivity and sensitivity, and the usefulness of colorimetry is declining.Comparisons have been carried out between ultraviolet and visible spectrometry and other methods, and agreement of the results has been good.993194 INFRARED ANALYSIS Infrared spectroscopy is one of the few specific methods available for residue analysis, but there are considerable difficulties involved in its application.The first difficulty, that is gradually being overcome, is the need for a relatively large amount of the pesticide to obtain a spectrum. The second difficulty is the need for extensive clean-up and this difficulty is accentuated by the concentration required before analysis. However, in spite of these difficulties infrared spectroscopy has often been used for the quantitative and qualitative analysis of residues of chlorinated pesticides. Its application in this way has been reviewedMarch, 19661 159 by Blinn and Gunther,lg5 Brucelg6 and by Frehse.lg7 These reviews give many references to the analysis of residues of aldrin, chlorbenside, chlordane, DDT, dieldrin, endrin, endo- sulphan, lindane, methoxychlor and tetradifon in a range of samples including crops, soils, air and water, and these references will not be repeated here.Blinn and Guntherlg5 have also reviewed the use of the different infrared regions and have compared the use of solutions, mulls and potassium bromide pellets. In much of the earlier residue analysis 60 pg or more of pesticide was required to obtain a recognisable spectrum. Smaller amounts could be analysed quantitatively by using the strongest absorption band for measurement, but such procedures lose some of the advantage of the specificity. Blinn et aZ.1g8 carried out measurements with 0.3 ml of carbon disulphide solution in a 5-mm light-path, sodium chloride cavity-cell and, under these conditions, 214 pg of aldrin in solution produced an absorbance (1250 cm-l) of 0-1 unit.Later, Johns and Braithwaitelg9 described a micro-specular attachment which reduced the amount of sample needed to the range 25 to 50 pg. Kreuger and \‘olkmann200 have des- cribed a micro attachment for an infrared spectrometer that will increase the instrument’s sensitivity 40-fold and will measure the spectrum of 0-1 ,ug of lindane. Chen201 has obtained recognisable infrared spectra with 1 pg of methoxychlor and other pesticides. Recently Crosby and Laws54 obtained recognisable spectra for 5-p1 solutions containing 5 pg of pesticides by using cavity-cells of 1-mm path length. This last work was described for organophosphorus compounds, but will be applicable to chlorinated pesticides, although not with quite the same limit of detectability.Sparagana and 1CIason202 have described a dual-beam condensing unit that uses reflecting- type optics and have obtained infrared spectra by using 0.05 pg of a compound. Although they did not apply the procedure to pesticides the method shows great promise for such applications. Infrared spectroscopy can often be used, after GLC, to confirm the identity of a component, and Giuffrida203 has described a useful method of trapping-out components from GLC columns directly on potassium bromide powder. The sensitivity of infrared spectroscopy has been increased considerably during recent years, and because of its specificity the method will assume increasing importance for residue analysis in the future. FLUORIMETKY Fluorimetry is a sensitive method for the analysis of many compounds, and characteristic activation or emission spectra can often be obtained.M a c D ~ u g a l l ~ ~ ~ and H ~ r n s t e i n * ~ ~ have reviewed the application of fluorimetry to residue analysis but make no mention of its application to chlorinated pesticides. Fluorimetry has not been used for the analysis of the chlorinated pesticides considered here, because they are insufficiently fluorescent. Although they could be converted to fluorescent compounds by suitable chemical methods, such studies are hardly worthwhile in view of the extensive clean-up that is necessary before fluorimetric analysis, and also because several sensitive methods are already available for the analysis. C H LO I< I h’ AT E D I N S E CTI C I D E S ,4 h’ D AC A R I C I D E S PAPEK CHROMATOGKAPHY Paper chromatography has been used e ~ t e n s i \ ~ e l y ~ ~ y206 ,20T *208 3209 for the separation of mixtures of pesticides in extracts of plants, animal tissues and dairy products, and for the qualitative and quantitative analysis of pesticides. Both aspects will be considcred here.The application of paper chromatography for clean-up has been discussed in a previous section. The RF values obtained by paper chromatography are useful for the identification of the components, but a single K , value is not sufficient for positive identification unless it can be used in conjunction with another parameter such as the GLC retention time. Paper chroma to- graphy is generally used not for clean-up of extracts, but for the identification of pesticides, and the clean-up by other methods is generally necessary to achieve the maximum sensitivity of detection.37 y 2 0 6 Early work on the paper chromatography o f pesticides has been reviewed by Block et aZ.211 and the more recent work has been summarised by Zweig212 and by McKinley.213 The paper chromatography of pesticides was described by Mitchell in a series of In one of these222 the chromatography of 114 pesticides including almost all of the compounds considered here was described.Mills37 showed that chlorinated pesticides in a range of fruits, dairy products and animal tissues, could be readily detected by using160 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF [AndySt, VOl. 91 paper chromatography and similar work was reported almost simultaneously by McKinley and Mahon.206 The basic techniques established by Mitchell, Mills, McKinley and Mahon or minor modifications of them are those used widely with success today.PAPERS, AND MOBILE AND STATIONARY PHASES- Whatman No. 1 filter-paper has often been used for paper chromatography, and if phenoxyethanol-silver nitrate is to be the spray reagent the paper is generally washed before the chromatography to remove background interference. Washing procedures have been described with water aqueous silver nitrate followed by water,206 and aqueous silver nitrate followed by ammonia - water.209 Most paper chromatography has been carried out with impregnated papers, and in Table VI are listed a few of the combinations of mobile and immobile phases that have been found to be useful for the separation of chlorinated pesticides, together with the corre- sponding RF values.The preferred system will depend on the compounds to be separated, and the use of different systems is recommended to obtain several RF values if more evidence of identification of a compound is desired. DETECTION- Phenoxyethanol- silver nitrate as a spray reagent followed by ultraviolet irradiation has been shown by to be capable of detecting as little as 0.01 pg of some chlorinated pesticides. has also shown that 4 to 5 minutes of ultraviolet irradiation is the optimum without the production of an excessive background, and he has also compared the limits of detectability with and without water-washing prior to chromatography.Although washing has been an accepted and recommended procedure for some time, these recent results show that the process has little effect on the limits of detectability for many chlorinated pesticides. Indophenol blue in the presence of an aliphatic acid226 and methyl yellow followed by ultraviolet irradiation227 have also been used as spray reagents for paper chromatography. Several, but not all, of the spray reagents used for TLC are also applicable to paper chromatography . When the pesticides are not resolved from one another or from co-extractives they can sometimes be identified by the use of specific spray reagents. TABLE VI RF VALUES OF CHLORINATED PESTICIDES BY PAPER CHROMATOGRAPHY R p values RL values (RF relative to lindane) I A 1.A - Component 2,2,4- 2,2,4- Mobile phase 2-Methoxy- Trimethyl Trimethyl pentane222 pentaneZo6 Immobile phase Soya-bean 2-phenoxy- 2-phenoxy- oil ethanol ethanol Aldrin . . . . .. Chlorbenside . . .. Chlordane . . .. Chlorfenson . . . . Chlorobcnzilate . . y-BHC.. . . .. op’-DDT .. .. pp’-DDT .. .. Dicofol .. .. Dieldrin . . .. Endrin .. .. Heptachlor . . .. Heptachlor epoxide . . Methoxychlor . . .. Oxythane . . .. Tetradifon . . .. Toxaphene . . .. 0.37 0.92 2.63 0.65 0.42 1.0 0.34 0.65 1.40 0.08 to 0-57 0.8 to 1.0 1-83 0.74 0.3 1 0.46 0.79 0.39 2.26, 0.52 - 0.80 1.98 0.34 0.67 1-66 0.69 0-30 0.31, 2-11 0-42 0.64 2-64, 1-55 0.41 0.64 1-48 0.3 1 0.94 2.11 0.38 0.77 - 0.68 0.30 0.67 - - 1-23 0.48 0.16 - 0.05 to 0.48 0.36 to 0.92 - and streak Figures in italics are the main components.40 per cent. aqueous pyrid ine*06 mineral oil 0.27 1.0 0-G1 streak 1.00, 1-28 1-69, 0.73, 0.30 0.55 0.55 1.09, 0.28, 0.93, 0.40 0.08, 0.33, 0.73 0.7 1 0-38 1.09 0.42 - - - 70 per cent. aqueous acetone206 mineral oil 0.10 1.0 0.32 0-18 1.00 1-12, 0.85, 0-55 0.18 0.18 0.73, 0.35, 0.09 1.82, 0.33, 0.14 0.45 0-15 1-24 - 0.11, 0.50March, 19661 CHLORINATED INSECTICIDES AND ACARICIDES 161 QUANTITATIVE ANALYSIS- Quantitative analysis of pesticides can be carried out after paper chromatography by measurement of the size or intensity (or both) of the separated spots and comparison with standards. The principles of such measurements for quantitative analysis by using paper chromatography and thin-layer chromatography are similar and are discussed together under the heading Thin-layer Chromatography. THIN-LAYER CHROMATOGRAPHY (TLC) TIX has been used many times for the qualitative and quantitative analysis of chlorinated pesticides and these aspects will be considered here.The application of TLC for the clean-up of extracts has been discussed briefly in a previous section. Conkin22s has reviewed the early work on the application of TLC to residue analysis, and other early work on the TLC of chlorinated pesticides has been summarised by Ganshert et aZ.229 Walker and Ber0za~~0 studied the separation of 68 pesticides by TLC, and Kovacs231 and Morley and Chiba232 have successfully applied the method to the analysis of residues of chlorinated pesticides in crops. Recently Abbott et aL2= have studied the separation of chlorinated pesticides by TLC over a wide range of conditions and some of their results are summarised in Table VIT.TABLE VII RF VALUES OF CHLORINATED PESTICIDES BY TLCW RF x looinsystem Compound Aldrin . . .. pBHC . . .. pp'-DDE . . . . op'-DDT . . . . pp'-DDT . . . . Dieldrin . . . . Endosulfan A . . Endosulfan B . . Endrin . . . . Heptachlor epoxide Methosychlor . . Heptachlor . . . . PP'-TDE . . , . 7 1 88 87 71 72 69 - - 82 - 66 - 2 98 58 98 90 91 58 - 98 - 77 3 73 87 74 78 53 - - 69 - 58 4 58 74 50 52 30 - - 48 38 67 - 5 69 37 62 58 54 48 52 52 62 36 46 - - 6 7 8 9 1 0 1 1 67 70 79 64 62 67 27 - 47 18 19 46 61 68 73 57 56 65 54 62 71 46 48 59 49 60 69 39 40 57 41 46 63 48 54 65 47 63 61 35 31 58 12 42 58 65 26 26 49 61 65 73 53 52 65 39 27 30 45 10 13 - 33 45 59 26 28 52 - - - - - - - - - - Key to systems 12 98 94 98 97 98 88 94 86 88 88 88 92 - 13 14 i5 82 95 70 78 95 65 73 89 50 69 89 42 52 37 12 64 65 17 9 4 2 61 51 13 78 95 58 57 49 17 57 71 25 55 78 - - - - System NO.1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Plate Silica gel - alumina (1 to 1) Silica gel - alumina (1 to 1) Silica gel Silica gel Silica gel Silica gel Silica gel Silica gel Silica gel Silica gel Silica gel Kiesclgu hr Alumina Alumina Silica gel ~ - 3 Mobile solvent Cyclohexane - liquid paraffin (20%) Cyclohexane - silicone oil (8%) Cyclohexane - hexane (1 to 1) Cyclohexane - benzene (1 to 1) - liquid paraffin (10%) Cyclohexane - liquid paraffin (20%) - dioxane (10%) Cyclohexanc - liquid paraffin (2076) - dioxane (5%) Cyclohexane - liquid paraffin (10%) - dioxane (3.5%) Cyclohexane - liquid paraffin (5%) - dioxane (2%) Light petroleum (40" to 60') - liquid paraffin (20%) Light petroleum - liquid paraffin (10%) Light petroleum - liquid paraffin (5%) - dioxane (1%) As 11 As 11 Hexane Hexane The measurement of the RiF value may assist in the identification of a chlorinated pesticide although a single RF value is insufficient evidence.Quantitative analysis may be carried out by measuring the spot area and intensity. To achieve the greatest sensitivity the layer is generally washed prior to the separation to remove interfering compounds from the absorbents and the extracts are often submitted to clean-up by other methods before the thin-layer chr~matography.~~~ However, Morley and Chiba232 were able to measure residues of aldrin, DDE, DDT and heptachlor in wheat, down to 0.1 to 0.2 p.p.m.(0.05 to 0.1 pg) without prior clean-up. After rigorous clean-up162 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF [Analyst, Vol. 91 of extracts, however, K o ~ a c s ~ ~ l was able to detect residues of many chlorinated pesticides in a range of foodstuffs at the p.p.b. (parts per thousand million) level. ADSORBENT AND DEVELOPING SYSTEM- Silica gel, alumina, kieselguhr and some mixtures of these have been used as adsorbents. Kieselguhr is reportedz33 to be of limited use for the separation of chlorinated pesticides and silica gel has been the most widely used. Chloroform alone or mixed with polar solvent~,2~0 hexane2= or h e ~ t a n e ~ ~ l and cyclohexane alone or mixed with polar solvents have been used successfully for development.The use of a simple system such as hexane or heptane and silica gel or alumina will effect the separation of many chlorinated pesticides.231 3233 I t is not possible to recommend one system for general application since no one combination of adsorbent and developing solvent will separate even the small number of compounds considered here. However, by suitable choice from one of the many systems now available230~231~233 any pair of compounds could be separated. Furthermore, Abbott et aZ.233 have shown that resolution of chlorinated pesticides, not possible at room temperature with a given system, may be effected at a higher or even lower temperature. DETECTION- The most commonly used locating agent is phenoxyethanol - silver nitrate followed by ultraviolet irradiation.K o ~ a c s ~ ~ * could detect 0.01 pg of aldrin, DIIE, heptachlor and its epoxide, DDT, TDE, endrin, dieldrin, methoxychlor and dicofol, 0.05 pg of BHC and 0.1 pg of toxaphene and chordane. The adsorbent layer was washed with water prior to the chromatography; the limits of detectability may be higher without this washing because of the presence of inorganic chlorides in the adsorbent. Morley and Chiba232 and Yamamura et aZ.234 used ammonium hydroxide in place of phenoxyethanol. Abbott et aL2% reported that treatment with ethanolic silver nitrate by ultraviolet irradiation was adequate for the detection of chlorinated pesticides on TLC. Abbott et aZ. obtained interesting results by using combinations of aqueous silver nitrate and a pH indicator (with or without ultraviolet irradiation) and recommended the use of bromophenol blue - silver nitrate,235 but did not report the limits of detectability.Other spray reagents that have been used for the detection of chlorinated pesticides on TLC include 0.1 N potassium ~ermanganate,"~ zinc chloride or iodine plus di~henylamine,~~T silver nitrate - formaldehyde - potassium hydroxide - nitric acid - hydrogen peroxide in succession,238 P-dimethylaminoaniline hydro~hloride,~~~ alcoholic o-toluidine or o-dianisidine,=O sulphuric iodine230 and bromine - fluorescein.230 M'ith several of these reagents ultra- violet irradiation is necessary. The limits of detectability obtained with these reagents are greater than those claimed by Kovacs, but many of them will detect 5 pg or less.Although silver nitrate in some form is the most common reagent the other reagents mya serve to increase the certainty of the identity of a particular spot. QUANTITATIVE ANALYSIS- The principles for the quantitative measurement of the spots of chlorinated pesticides in thin-layer and paper chromatography are the same as that for other compounds as outlined by Purdy and Truter,241 and by T r ~ t e r . ~ ~ ~ Often the spot area alone has been measured and is related to the amount from a calibration graph, preferably obtained by the chromato- graphy of standards on the same plate. The comparison is often made visually how- ever.37,206,232,243 The area of the spot can be related to the amount of compound present211 but the relationship is not rectilinear.Evans210 found that a rectilinear relationship existed between spot area and log (amount) in the range 2.5 to 14 pg for several chlorinated pesticides, and he obtained a precision of 10 per cent. for the measurement of 2.5 pg or more of these pesticides with paper chromatography. Purdy and T r ~ t e r ~ ~ l have reported excellent repro- ducibility ( * 6.6 per cent. in the 2 to 30 pg range) with a rectilinear calibration-graph obtained by plotting (area): against log(weight), a relationship first used by Fisher et aZ.244 Zweig212 obtained rectilinear plots in the 0.5 to 44pg range for DDT by plotting amount against area and density. I t is likely that relationships that consider both area and density will give the most consistent results for a wide range of compounds.Densitometric measurements may be made photometrically by scanning the plate or paper, or by scanning a photograph of them.March, 19661 TLC is rapid and quantitative in future years. A difficultv CHLORINATED INSECTICIDES AND ACARICIDES 163 the equipment is inexpensive and it can be used for clean-up, qualitative analysis. These advantages will undoubtedly be exploited even further THE POSITIVE IDENTIFICATION OF PESTICIDE RESIDUES )ecoming more and more prominent in this field of anal]& is that of establishing t h i identity %f a residue. Mani naturally occurring products *in the extract can respond to the analytical procedure and can be mistaken for pesticides when a valid control is not available.Such components are not always removed by the clean-up procedure that is used. I;or this reason GLC, total halide analysis, polarography, bioassay, colorimetry ultraviolet analysis, fluorimetry, thin-layer or paper chromatography cannot normally be regarded as specific methods, and cannot usually provide positive identification of a given component in the absence of a valid control. Inirared analysis can be reasonably specific but relatively large amounts of pesticide are required as well as rigorous clean-up of the extracts. These problems are being overcome gradually, and infrared analysis has been used successfully for the positive identification of residues of chlorinated pesticides after clean-up by gas - liquid chromatography, column chromatography or by thin-layer chromatography.Mass spectrometry can generally provide a positive identification of a cornponcnt, but little has been reported so far on the application of this technique to residue analysis. The problems are similar to those encountered with infrared analysis, in that rigorous clean-up and relatively large amounts of compound are required. However, Ryliage245 has obtained recognisable mass spectra with 20 ng of esters of long-chain carboxylic acids that were passed directly from a capillary GLC into a mass spectrometer. Whilst such equipment is expensive it merits application for identification of residues. Such a procedure may perhaps be more convenient than infrared spectroscopy as the effluent from the GLC column is already in the vapour phase, and can be fed directly into the mass spectrometer with perhaps only limited interference from co-extractives and without the need for trapping-out components.These two procedures can, at best, offer conclusive evidence of identity. The specificity of other methods can be improved, but such improvements cannot make interpretations from them completely unambiguous. A single retention time obtained by GLC or a single RE’ value obtained by thin-layer or paper chromatography is not sufficient for the positive identification of a component. Whilst the measurement of several retention times or RF values with different operating conditions may show that the component in question is not present, such evidence cannot be used as proof of the presence of the component. Improvements in specificity can be obtained by the combined use of different clean-up procedures.The use of liquid - liquid partition and column chromatography or chemical treatment prior to GLC improves the specificity, and the additional use of thin-layer chromato- graphy prior to GLC increases the specificity even further. Increased certainty of identification can better be obtained by analysis using two or more methods. This has been done successfully in the past and extracts have been analysed by colorimetry and bioassay, by total chlorine and bioassay and by GTX. Such combined procedures cannot always be applied, however, especially for the analysis of low residues as few of the other methods are as sensitive as GLC for the analysis of chlorinated pesticides. If infrared analysis or mass spectrometry cannot be used, reasonable specificity can be achieved if the extract is subjected to partition, column chromatography and thin-layer chromatography in turn, and is analysed by gas - liquid chromatography and by another procedure such as colorimetry or bioassay.Beroza and Bowman6’ 768 have used a combination of liquid partition and GLC for the identification of pesticides by using the GLC retention time and the partition coefficient as parameters to identify a component, and this approach shows promise for the positive identification of pesticides. RECOMMENDED METHODS In the previous sections, work on the chlorinated pesticides has been reviewed in a general way. In this last section, procedures will be recommended for the extraction, clean-up and analysis which at the present time seem to be the best.Procedures that can be applied to whole groups of compounds will be outlined first. Then each chemical will be considered164 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF [Analyst, Vol. 91 individually, pointing out any particular difficulties in the analysis, referring to published work on each chemical to illustrate the use of the recommended methods on a variety of substrates, and giving alternative methods. GENERAL PROCEDURES EXTRACTION- soizs- Mix a suitable weight of wet soil with anhydrous sodium sulphate and tumble them end- over-end with a solvent mixture. A ratio of 1 g of soil to about 0.5 g of sodium sulphate and 2 ml of a mixture of 20 per cent. acetone in hexane is recommended, tumbling for 1 hour.Filter the mixture and remove the water-soluble portion by water washing. crops- Macerate a convenient weight with anhydrous sodium sulphate and a mixture of water- immiscible and miscible solvents, benzene or hexane and acetone or isopropanol. A ratio of 1 g of crop to about 0.5 g of sodium sulphate and 2 ml of a 1 to 1 volume solvent mixture, with blending for 1 minute is usually sufficient. Filter and remove the water-soluble portion by water washing. Animal tissues and products- a suitable solvent such as hexane. Mills% already described may be used. CLEAN-u P- For the removal of polar interference use column chromatography with adsorbents such as alumina, Florisil or magnesia. Elute the non-polar compounds such as aldrin, DDE, DDT and heptachlor with hexane, and the more polar ones such as dieldrin, endrin and the oxidation products of chlorbenside with hexane containing a small amount of acetone or ether.For non-polar interference, such as lipid, use liquid - liquid partition with hexane - acetonitrile,62 hexane - dimethylformamidegO v63 or hexane - dimethylsulphoxide64 as solvent pairs. To determine low residue levels on materials with a high fat content, further clean-up by using column chromatography is usually necessary. It should be stressed that while these are the general methods of clean-up, others referred to in a previous section may prove helpful for particular problems. Grind the tissue with anhydrous sodium sulphate or sand and extract by warming with Alternatively, the methods of Langlois et al.36 or of ANALYSIS- Gas - liquid chromatogyaphy- The operating conditions given in the papers of Goodwin et al.,65 Burke and Holswade102 and Burke and Giuffrida1l8 should be consulted.The following points will serve as guides in the choice of conditions for particular systems. A non-polar silicone stationary phase has the best separating power; other thermally-stable polar phases may be needed to give particular separations or additional evidence of identification. The following are recom- mended to minimise the decomposition of pesticides ; on-column injection, suppression of support activity by treatment with Epikote resin or hexamethyldisilazane, glass or other non-reactive materials for the column and the use of column temperatures as low as con- veniently possible, General screening methods with GLC, designed to reveal the presence of chlorinated pesticides, have been reported by Goodwin et aZ.,95 Kaufman and Jackson,246 McCully and McKinley,38 Minyard and Jackson135 and Wells.=' T hin-lay er chromatography- Where GLC equipment is not available TLC offers an inexpensive and suitable alternative with good separating power and fair sensitivity.Like paper chromatography, it is a useful complementary technique for identification purposes. The best separations have been achieved with silica gel and a non-polar eluting solvent such as hexane or heptane. Alumina gives poorer separations, but if silver nitrate is used as detectinp apent it gives better sensitivitv. A 300-w layer of adsorbent is preferred sinceMarch, 19661 CHLORINATED INSECTICIDES AND ACARICIDES 165 The best sensitivities have been obtained with Mitchell’s silver nitrate - phenoxyethanol spray reagent231 (i) AZdrin- INDIVIDUAL PROCEDURES c1 c1 Materials treated directly or indirectly with aldrin must be examined for both aldrin and dieldrin (its oxidation product).Both products are stable to the GLC operating conditions described above. On a silicone stationary phase, aldrin is difficult to resolve from dicofol and o$’-TDE olefin but these are separable on more polar phases. Residues to a level of 0.01 p.p.m. can be determined readily in crops and tissues. The GLC method has been used for the determination of aldrin in soil and root crops by Lichtenstein and his c o - w ~ r k e r s , ~ ~ ~ ~ ~ ~ ~ by Stewart et aZ.250 and by Decker et in grapes by Hascoet and Adam252; in vegetables and dairy products by Watts and Klein1S6; in milk by Henderson2M; and in water by Hindin et aZ.24 Alternative methods to GLC are the phenylazide colorimetric method and bioassay, both of which are discussed in detail by Porter.254 (ii) y-BHC (Linda?ze)- c1 co c1 C1 Cl yBHC may be measured at the residue level by gas - liquid ~ h r o m a t o g r a p h y l ~ ~ ~ ~ ~ ~ 9 and this is the recommended method of analysis. Electron-capture detectors have a large response to this compound and residues of 0.01 p.p.m.can be determined readily and the limit of detectability is even lower. GLC has been applied to the analysis of y-BHC in a wide range of crops,ll 946 9659255 dairy I t is rarely necessary to analyse samples for residues of the other isomers of BHC but the isomers can be conveniently separated by GLC,102J18,257 TLC229 or paper chromato- g r a ~ h y .~ ~ 8 9259 The Schechter - Hornstein colorimetric procedure or modifications of it have been used by many workers for the analysis of a wide range of samples.260t0268 The collaborative studies of the Schechter - Hornstein method are discussed by Klein269 but the procedure is much less sensitive than GLC. Other methods of analysis that have been used include bioassay,l77 p ~ l a r o g r a p h y ~ ~ ~ and infrared spectroscopy.271 9272 and tissues.255 (iii) ChZorbenside (Mitox)- Chlorbenside can be analysed with the GLC conditions described previously and is resolved from the other pesticides considered here.GLC does not seem to have been reported for residue analysis of chlorbenside but the previous work1029118 has shown this to be feasible. GLC of the metabolites of chlorbenside, the sulphoxide and sulphone does not seem to have been reported but should be possible. Gunther, Blinn and Barnes273 have measured residues of chlorbenside in pears by infrared spectroscopy. The method is also suitable for analysing for the sulphoxide oxidation product166 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF [Analyst, 1'01. 91 of chlorbenside. The sample is extracted with hexane and is subjected to column chromato- graphy which separates the chlorbenside and its sulphoxide. The separated sulphoxide and chlorbenside are determined by infrared spectroscopy.The alternative colorimetric procedure of Higgons and K i l b e ~ ~ ~ ~ involves oxidation of the chlorbenside to the sulphone, followed bjr nitration and spectroscopic measurement at 575 mp. Higgons and Kilbey did not separate the chlorbenside and its metabolites before analysis, but there is no reason why the separation procedure by Gunther could not be used for this. This separation procedure may also be of use before GLC analysis. (iv) Chlordaue- c1 c1 Chlordane is produced by the chlorination of chlordene and contains 60 to 75 per cent. of the p- and y-chlordanes (the trans and cis isomers, respectively), and 25 to 40 per cent. of analogous materials containing 6, 7 and 9 chlorine atoms. The gas chromatogram of technical material has a characteristic appearance, the peaks due to p- and y-chlordane predominating.N'hile in some respects the gas chromatography of chlordane residues is made easier by the readily identifiable pattern, the feasibility of distinguishing peaks from natural materials and from other pesticides that may be present, such as clilorfenson, chlorbenside and the major isomer of endosulfan, is not an easy matter, and must be overcome by prior clean-up or by the use of more than one stationary phase. Chlordane has rather specialised uses and little work has been published on residues arising from them, but reference may be made to the paper of Gutenmann and Lisk255 where a sensitivity of 0.01 p.p,m. of chlordane in soil was achieved. The alternative method is a colorimetric one, based on its reaction with methanolic potassium hydroxide and diethanolamine, details of which are gixren by The acaricide chlorfenson can be analysed satisfactorily by gas - liquid chromatography under the conditions previously described, but it is not readily resolved from endosulphan and p-chlordane.Such resolution might be accomplished by using other, perhaps more polar, stationary phases, but the GLC of chlorfenson has not been studied in detail for residue analysis. Butzler et aZ.91 have reported a colorimetric procedure that is sensitive to less than 5 pg of chlorfenson in orange pulp. In this procedure the chlorfenson is extracted with benzene, and the extract is hydrolyscd with alcoholic potassium hydroxide to convert the chlorfenson to $-chlorophenol which is separated by steam distillation and nitrosated.The product is then separated by- column chromatography before spectroscopic analysis at 430 mp. The analysis for residues of chlorfenson does not seem to have been reported very frequently in recent years. (vi) ChZorobenzilate- GLC promises to be a sensitive and convenient method for such analysis. Other colorimetric procedures have been described.g* 3276 9 2 7 7 CO,C,H, I OH The acaricide chlorobenzilate may be analysed with good sensitivity by gas - liquid chromatography and is stable under the conditions described. I t is readily resolved from the other acaricides considered here. Its retention time, however, is close to that of 09'-DDT and $$'-TDE when a column temperature of 200" C is used.l18March, 19661 CHLORINATED INSECTICIDES AND ACARICIDES 167 The analysis of residues of chlorobenzilate in grapes and cotton seed with a sensitivity of 0.05 p.p.m.has been carried out successfully by microcoulometric GLC278 with 20 per cent. Dow 11 silicone grease on Chromosorb P. Benzene was used as the extraction solvent and clean-up was by partition into nitromethane followed by column chromatography on Florisil for cotton-seed extracts. Infrared spectroscopy was used to confirm the identity of the residue. The use of electron-capture has not yet been reported for the determination of chloro- benzilate residues but the work of Burke and Guiffridalls shows that this should be possible with high sensitivity. A suitable alternative method of analysis is the Delley colorimetric procedure as modified by H a r r i ~ ~ 7 ~ and described in detail by Margot and Stammbach.280 In this procedure the chlorobenzilate is extracted with benzene, saponified with methanolic alkali to form dichloro- benzilic acid.which is extracted and nitrated and the absorption is measured at 538mu. Clean-up with Nuchar carbon was used for grapes. This procedure is sensitive to 2 pg of chlorobenzilate and haibeen applied to of samples.279 Blinn et a1.28l have described a similar procedure but without step, and have applied this to analysis of residues in citrus. a wide range the nitration (vii) DDT, TDE, DDE- DDT and the The technical cc1, pp’-DDT The analvsis of residues of the maior and minor constituents of technical metabolic priducts is one requiring carehl experimentation and interpretation. material contains upwards of 70 per cent.of the $p’-isomer, the bulk of the remainder being the o$’-isomer, but some f$’-TDE and a small amount of op’-TDE are usually present. The principal metabolic product of DDT is DDA, which can be analysed by GLC after methylation. Other metabolic products are the olefin DDE, but TDE may also be produced and the olefin of TDE. In addition DDT may undergo thermal and catalytic conversion to DDE or TDE. Thus an extract of crop or tissue could conceivably yield DDT and TDE as such, or as dehydrochlorinated products, each as 99’- or o$’-isomers; and to add to the difficulty, derivatives may arise as impurities in the technical material, from metabolism or from decomposition. Exceptional care must therefore be taken when interpreting chromatograms.On a silicone stationary phase three pairs of the DDT analogues are difficult to resolve and require other stationary phases to show adequate separation. These pairs are $$‘-TDE olefin and of’-DDE; fp’-DDE and 09’-TDE; and $9’-TDE and op’-DDT. The latter two pairs may also be separated by conversion to their olefins by treatment with alkali, followed by GLC.141 ~ a t e r , 2 ~ W crops,136 ~lothing,~8~ dairy products,152$2~,256 tissues,3g 9285,286 92879288 and the total diet289 with a sensitivity sometimes of less than 0.01 p.p.m. Colorimetric methods of analysis have been reviewed by M i s k ~ s . ~ ~ ~ GLC has been used for the analysis of residues of DDT and its derivatives in (viii) Dico fol (Keltha%e)- OH c1 --c1 cc1, Dicofol is reported212 to decompose almost quantitatively during GLC and although Burke and Johnsonlol and Burke and Holswadelo2 have reported retention results for dicofol they have not shown that the response that they obtained was from dicofol itself.However, Gunther et aZ.129 have shown that, when the GLC column (silicone on firebrick) was “condi- ditioned” to dicofol the extent of decomposition was small, and that 90 to 95 per cent. of the dicofol was not decomposed during the chromatography, and the remainder was converted to 4,4’-dichlorobenzophenone. Thus, GLC shows considerable promise for the analysis for residues of dicofol, and some results have been given in a study of total-diet samples.28s168 BEYNON AXD ELGAR: ANALYSIS FOR RESIDUES OF [ArtdySt, Vol.91 Colorimetric analysis has been carried out successfully for dicofol in a wide range of crops and animal products. The basic procedure is that used by Rosenthal et aZ.2g1 involving hydrolysis of dicofol to chloroform which is determined colorimetrically by the Fujiwara reaction. Gordon, Haines and have carried out the hydrolysis with sodium hydroxide (for crops) or with tetraethylammonium hydroxide (for fatty samples) and their procedure has been described in detail by Gordon and S c h ~ c k e r t . ~ ~ ~ This procedure will detect 10 pg of dicofol and it has been applied to the analysis of dicofol in milk,292 butter-fat and animal body fat,294 and is applicable to a range of crops and animal products. Similar procedures have been used for a range of samples by other workers,295~296,297 and Gunther and Blinn298 have described an alternative procedure involving hydrolysis of dicofol to 4,4’-dichlorobenzo- phenone which is measured by ultraviolet spectroscopy.(ix) Dieldrin- Dieldrin is stable to the operating conditions described previously for GLC analysis. On non-polar stationary phases the retention times of dieldrin and +$’-DDE are almost coincident, and op’-TDE is also close. It is essential therefore to acquire complementary evidence for the identity of die1dri11.l~~ It is fairly stable to metabolic change, though several workers have reported metabolites.2gg 9300 3301 9302 Recent examples of the analysis of dieldrin residues by GLC are those carried out by Hardee et aZ.,303 by Morley and Chiba304 and Decker et aZ.251 on soil, by Harvey and Harvey on pasture,305 by Williams, Mills and hlcDowel1 on milk,256 by Hunter et aZ.286 and Dale and ~Quinby~~7 on human fat and by on total-diet samples.Residue levels of 0.01 p.p.m. can be attained without excessive clean-up. The alternative specific method for dieldrin is the phenylazide colorimetric procedure discussed in detail by Porter.306 (x) Endoszdfan (Thiodan)- c1 C1 Endosulfan has two stereoisomers, the lower-melting isomer constituting two-thirds of the technical product, the higher-melting isomer being the other major component. These can decompose to endosulfan alcohol, and the so-called endosulfan ether may also be present in technical material. The alcohol may also be produced by metabolism, and the presence of endosulfan sulphate from metabolic oxidation has also been re~orted,~O73~~8 so that once again the application of one technical material can give rise to a complex residue analysis.Zweig et u Z , ~ ~ have used GLC as a means of separation in their work on the infrared determination and identification of endosulfan residues. Details of the GLC microcoulometric procedure are given by Graham et aZ.309 but few results specifically relating to residues of endosulfan have been reported.ggJ05,307 p 3 l o The major component of endosulfan may be difficult to resolve under normal GIX operating conditions from p- and y-chlordane isomers and from chlorfenson, and the other isomer from endrin or chlorobenzilate, but the presence and the ratio of the several peaks from technical endosulfan gives some evidence of identity.March, 19661 CHLORINATED IXSECTICIDES AND ACARICIDES (xi) Endrin- c1 169 c1 Although endrin is sensitive to temperature,llg it can be analysed without decomposition by GLC.65 Endrin has a less toxic product, the so-called “delta keto,” an isomeric ketone that occurs in plants but not in animals.Endrin is resolved from other common pesticides on a silicone stationary phase. The pattern of peaks due to decomposition on chromato- graphy at high temperature could be used as an aid to identification. GLC analyses of endrin residues in alfalfa,255 water,24 milk,256 tissue39 and the total diet2sg have been reported in recent years. Colorimetric procedures for the analysis of residues of endrin have been reviewed by Terriere.311 (xii) Heptnchlor and heptnchlor epoxide- c1 Like aldrin, heptachlor forms an epoxide in biological media, so that both must be deter- mined as residues following heptachlor applications. Both are thermally stable and can be chromatographed on the sub-microgram scale without trouble. Rusk and Fahey312 have pointed out that y-chlordane present in technical heptachlor can form a significant proportion of the total residue, and its retention time on non-polar stationary phases is similar to that of heptachlor epoxide. They have given details of a chromatographic separation of heptachlor, its epoxide and y-chlordane on Florisil. Recent residue work carried out by GLC include that in s0il,2489250 crops,248 9250 milk,256 9313 tissue66 and the total diet.289 Colorimetric methods have been reviewed by Bowery.314 (xiii) Methoxychlor- CCI, H Methoxychlor may be analysed by gas - liquid chromatography under the standard conditions described previously.Because of its long retention time there is little interference from other chlorinated pesticides. The method has not been widely reported for residue analysis but it has been used by BaeW who also described a suitable clean-up procedure, and by Williams.289 A colorimetric method of analysis was developed by Fairing and W a r r i n g t ~ n ~ ~ and is described in detail by Lowen et aZ.315 The method, which is applicable to crops and animal products, involves partitioning of the pesticide into nitromethane followed by dehydro- chlorination, column chromatography and sulphonation, to give a coloured product that is measured spectroscopically.The method is sensitive to 2 pg of methoxychlor. This procedure was used by Cluett et nl.316 in combination with total halide analysis to determine methoxy- chlor and its possible metabolites in milk. Other methods of analysis have been summarised by Lowen et aL315170 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF [AfldySf, Vol. 91 (xiv) Oxythane (Neoiran)- C l e OCH,O Oxythane was not included in the work of Burke and Holswadelo2 or of Burke and JohnsonlOl but it is very likely that the analysis for this compound can be carried out by GLC. Little work has been published on the analysis for residues of oxythane or on its thin-layer and paper chromatography . Gunther and Blinn3I7 have described a colorimetric procedure involving extraction with benzene followed by hydrolysis with hydrobromic acid to form 9-chlorophenol.The phenol is separated from interfering compounds by steam distillation, and is reacted with 4-amino- antipyrine, before spectroscopic measurement at 510 mp. (xv) Tetradi f o n (Tedion)- c1 / Ci Gas - liquid chromatography is suitable for the analysis of residues of tetradifon, and microcoulometric detectors have been used by Coulson et aZ.,96 Cassilg9 and by Burke and Mills105 for the analysis of a range of crops, and less than 5 pg of tetradifon could be detected. The use of electron-capture detection would improve the sensitivity considerably. The GLC of tetradifon has been carried out successfully by other workers who have used both micro- coulometric and electron-capture detection.102s118 A colorimetric procedure based on the Fujiwara reaction was developed by Fullmer and CassiPls and is described in detail by Cassil and Yaffe319 who have also considered many of the possible sources of interference in the procedure. Gunther and Blinns9 have described a total chlorine method, and Gunther et have measured tetradifon residues by infrared analysis with chromic oxide - acetic acid for the clean-up. (xvi) Toxaphene- As toxaphene is a multi-component mixture of chlorinated terpenes, it is not possible to recommend a specific method. Residue analysis has generally been carried out by a totd- chlorine procedure or the zinc chloride - diphenylamine colorimetric method of Graupner and D ~ n n , ~ ~ l both of which have been described by D ~ n n .~ ~ ~ Nikolov and done^^^^ have recently described a modification to the colorimetric procedure that increased the sensitivity 10-fold. The GLC method with halogen-selective detection is an advance on these in that sensi- tivity is improved and some semblance of specificity is offered due to the pattern of peaks produced. However, at low residue levels this specificity is unreal as the presence of peaks from natural products or other pesticides would be impossible to distinguish from the Toxaphene components. After rigorous clean-up, determinations of fairly low residue concentrations are possible on short columns which, having poor efficiency, give a single or only a few peaks for the Toxaphene mixture.324 An attempt to analyse total diets for toxaphene residues has been reported.289 We would like to thank Mr.E. S. Goodwin, Mr. R. Goulden, Mr. D. S. Penny, Mr. A. Richardson and Mr. P. C. R. Webb for reading the manuscript and for their helpful advice. REFERENCES 1. Zweig, G., Editor, “Analytical Methods for Pesticides, Plant Growth Regulators, and Food 2. Huddleston, E. W., Thompson, K. H., Gyrisco, G. G., Lisk, D. J., Kerr, T. W., jun., and Olney, 3. Van Middelem, C. H., Wilson, J. W., and Hanson, W. D., Ibid., 1956, 49, 612. 4. Poos, F. W., Dobbins, T. N., and Carter, R. H., U.S. Department of Agriculture, Bulletin E-793, 6. Lykken, L., Mitchell, L. E., and Woogerd, S. M., J . Agric. Fd Chem., 1967, 5, 501. 6. Lykken, L., in Gunther, F. A., Editor, “Residue Reviews,’’ Springer-Verlag, Berlin, Volume 3, 7.Lichtenstein, E. P., Mueller, C. H., Myrdd, G. R., and Schulz, K. R., J . Econ. Ent., 1962, 55, 216. 8. Garber, M. J., in Zweig, G., 09. cit., Volume 1, p. 491. Additives,” Academic Press, New York and London, Volumes 1 to 4, 1963-64. C. E., J . Econ. Ent., 1960, 53, 1078. 1950. 1963, p. 19.9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. March, 19661 CHLORINATED INSECTICIDES AND ACARICIDES 171 Westlake, W. E., Analyt. Chem., 1959, 31, 724. Bann, J. M., Paper presented at the 131st American Chemicd Society Meeting, Miami, April, 1957.Goulden, R., Qualitas PI. Muter. Veg., 1964, 11, 381. Koblitsky, L., and Chisholm, R. D., J . A s s . 08. Agric. Chem., 1949, 32, 781. Lichtenstein, E. P., and Schulz, K. R., J . Econ. Ent., 1960, 53, 192. Taschenberg, E. F., Mack, G. L., and Gambrell, F. L., J . Agric. Fd Chem., 1961, 9, 207. Shell Method Series, SMS-551/55. Heinisch, E., NachrBl. dtsch. PJSchutzdienst, Berlin, 1959, 13, 161. Thornburg, W. W., in Zweig, G., op. cit., Volume 1, p. 87. Van Middelem, C. H., in Zweig, G., 016. cit., Volume 1, p. 25. Klein, A. K., J . Ass. Off. Agric. Chem., 1958, 41, 551. -, Ibid., 1960, 43, 703. Klein, A. K., Laug, E. P., and Sheehan, J. D., jun., Ibid., 1959, 42, 539. Hardin, L. J., and Sarten, C. T., Ibid., 1962, 45, 988.Mills, P. A., Onley, J . H., and Gaither, €3. A., Ibid., 1963, 46, 186. Hindin, E., May, D. S., and Dunstan, G. H., in Gunther, F. A., op. cit., Volume 7, 1964, p. 130. Rosen, A. A., and Middleton, F. M., Analyt. Chem., 1959, 31, 1729. Teasley, J. I., and Cox, W. S., J . Amer. Wat. Wks ,4ss., 1963, 55, 1093. Kahn, L., and Wayman, C. H., Analyt. Chem., 1964, 36, 1340. Eidelman, M., J. Ass. Off. Agric. Chem., 1963, 46, 182. -, Ibid., 1962, 45, 672. Lampert, L. M., J . Dairy Sci., 1964, 47, 1013. O’Donnell, A. E., Neal, M. M., Weiss, F. T., Bann, J . M., DeCino, T. J., and Lau, S. C . , J.Agric. O’Donnell, A. E., Johnson, H. W., jun., and Weiss, F. T., Ibid., 1955, 3, 757. Prickett, C. S., Kunze, F. M., and Laug, E. P., J . Ass. 08. Agric. Chem., 1950, 33, 880.illills, P. A., Ibid., 1961, 44, 171. Onley, J. H., Ibid., 1964, 47, 317. Langlois, B. E., Stemp, A. R., and Liska, B. J., J . Agric. Fd Chem., 1964, 12, 243. RiIills, I?. A., J . A s s . Off. Agric. Chem., 1959, 42, 734. McCully, K. A., and McKinley, W. P., Ibid., 1964, 47, 652. Taylor, A,, Rea, R. E., and Kirby, D. R., Analyst, 1964, 89, 497. de Faubert Maunder, M. J., Egan, H., Godly, E. W., Hammond, E. W., Roburn, J., and Thomson, Krzcminski, L. F., and Landmann, W. A., J . Agric. Fd Chem., 1963, 11, 81. Moddes, R., J. Ass. Ojf. Agric. Chem., 1961, 44, 169. Moats, W. A., Ibid., 1962, 45, 355. Coulson, D. M., and Barnes, E. G., Stanford Hes. Inst., Pesticide Res. Bull., 1963, 3, No. 2. Cassil, C. C., Gortner, W., and Stoner, H., quoted in Zweig, G., op.cit., Volume 1, 1962, p. 97. Baetz, R. A., J . Ass. Off. Agric. Chem., 1964, 47, 322. Moats, W. A., Ibid., 1964, 47, 587. Coulson, D. M., Stanford Res. Inst., Pesticide Res. Bull., 1962, 2, No. 4. Wheatley, G. A., Hardman, J. A., and Strickland, A. H., PI. Path., 1962, 11, 81. hbdallah, M. D., and Landheer, C. A., J . Chromat., 1962, 9, 245. Hoskins, W. M., Erwin, W. R., Miskus, R., Thornburg, W. W., and Werum, L. N., J . Agric. Coulson, D. M., Cavanagh, L. A., and Stuart, J., Ibid., 1959, 7, 250. Zweig, G., Archer, T. E., and Rubenstein, D., Ibid., 1960, 8, 403. Crosby, N. T., and Laws, E. Q., Analyst, 1964, 89, 319. Calderbank, A., Morgan, C. B., and Yuen, S. H., Ibid., 1961, 86, 569. Calderbank, A., and Yuen, S. H., Ibid., 1965, 90, 99. Plapp, F. ?IT., and Casida, J.E., Analyt. Chem., 1958, 30, 1962. Cueto, C., Barnes, A. G., and Mattson, A. M., J . Agric. Fd Chem., 1956, 4, 943. Heinisch, E., and Neubert, P., J . prakt. Chem., 1963, 22, 267. Abbott, D. C., and Thomson, J., Chem. & Ind., 1964, 481. Taylor, A., and Fishwick, B., Lab. Pract., 1964, 13, 525. Jones, L. R., and Riddick, J. A., Analyt. Chern., 1952, 24, 569. Burchfield, H. P., and Storrs, E. E., Contr. Boyce l’homson Inst. PI. Res., 1953, 17, 333. Haenni, E. O., Howard, J. W., and Joe, It-. L., jun., J . Ass. 08. Agric. Chem., 1962, 45, 67. Goodwin, E. S., Goulden, R., and Reynolds, J. G., Analyst, 1961, 86, 697. Taylor, A., Ibid., 1962, 87, 824. Beroza, M., and Bowman, M. C., Analyt. Chem., 1965, 37, 291. Fairing, J. D., and Warrington, €1. B., Adv.Chem. Ser., 1950, 1, 260. Williams, D. W., J . Ass. 08. Agric. Chem., 1957, 40, 254. Anglin, C., and McKinley, W. P., J . Agric. Fd Chenz., 1960, 8, 186. McKinley, W. P., Savary, G., and Webster, C., Ibid., 1962, 10, 226. McKinley, W. P., and Savary, G., Ibid., 1962, 10, 229. McCully, K. A., and McKinley, W. P., J . Ass. Off. Agric. Chem., 1964, 47, 859. McKinley, TV. P., Coffin, D. E., and McCully, K. A., Ibid., 1964, 47, 863. Gunther, I;. A., and Blinn, R. C,., J , Agric. Fd Chem., 1953, 1, 325. Cueto, C. J., jun,, Ibid., 1960, 8, 273. Fd Chem., 1954, 2, 573. J., Ibid., 1964, 89, 168. Fd Chem., 1958, 6, 914. I , J . Ass. Ofl. Agric. Chem., 1965, 48, 358. -~172 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 9 9 . 100.101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119. 120. 121. 123. 123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. 137. 138. BEYNON AND ELGAK: ANALYSIS FOR RESIDUES OF j’ilqzalyst, Vol. 91 Bann, J . M., Lau, S. C., Potter, J . C., Johnson, H. W., O’Donnell, A. E., and Weiss, F. T., Ibid., 1958. 6, 196. Carter, R. H., I n d . Engng Chem., Analyt. Ed., 1947, 19, 54. Frawley, J. P., and Davidow, B., J . A s s . Off. Agric. Claem., 1949, 32, i58. Tufts, L. E., Darling, G. W., and Kimball, R. H., Ibid., 1950, 33, 976. Meyer, C. F., Malina, M. A., and Polen, P. B., J . Agric. Fa? Chem., 1960, 8, 183. Helrich, K., Hansens, E. J . , and Granett, P., Ibid., 1958, 6, 281. Albert, R. A., J . Ass. Off. Agric.Chem., 1964, 47, 659. Schechter, M. S., Pogorelskin, M. A., and Haller, H. L., I n d . Engng Chem., Analyt. Ed., 1947, Davidow, B., J . Ass. Off. Agric. Chem., 1950, 33, 130. Bradbury, P. R., and Standen, H., J . Sci. Fd Agric., 1954, 5, 252. Gunther, F. A., Blinn, R. C., and Ott, D. E., J . Ass. Off. Agric. Chenz., 1962, 45, 359. Gunther, F. A., and Blinn, K. C., “Analysis of Insecticides and Acaricides,” Interscience Pub- Gunther, F. A., and Jeppson, L. R., J . Econ. Ent., 1954, 47, 1027. Butzler, G. J., Luce, E. N., and Wing, R. E., J . Agric. Fd Chem., 1957, 5, 42. Gunther, F. A., and Blinn, R. C., op. cit., p. 333. Ott, D. E., and Gunther, F. A., J . Agric. Fd Chem., 1964, 12, 239. Clifford, P. A., J . A s s . Off. Agric. Chem., 1947, 30, 337. Goodwin, E.S., Goulden, R., Richardson, A., and Reynolds, J. G., Chem. & I d . , 1960, 1220. Coulson, D. M., Cavanagh, L. A,, Dc Vries, J . E., and Walther, B., J . Agric. Fd Chem., 1960, Clark, S. J., Paper presented a t the 140th American Chemical Society Meeting, Chicago, September, Adlard, E. R., and Whitham, B. T., in Desty, D. H., Editor, “Gas Chromatography 1958,” Butter- Cassil, C. C., in Gunther, I?. A., op. cit., I‘olume 1, 1962, p. 37. Challacombe, J . A., and McXulty, J . -I., iiz Gunther, F. A., op. cit., Volume 5, 1964, p. 5 i . Burke, j., and Johnson, L., J . Ass. OH. Agric. Chem., 1962, 45, 348. Burke, J., and Holswadc, \IT., Ibid., 1964, 47, 845. Coulson, D. M., and De Vries, J. E., Stanford Res. Inst., Tech. Rep. No. I I , Report No. 6, 1958. Coulson, D.M., De Vries, J . E., and Walther, B. A., Stanford Res. Inst., Tech. Rep. No. I V , Report Burke, J., and Mills, P. A., J . Ass. 08. .4gric. Chem., 1963, 46, 177. Beckman, H., and Bevenue, A., J . Agric. Fd Chem., 1964, 12, 245. Coulson, TI. M., Huene, A. S., and Cavanagh, L. A., Stanford Res. Inst., Tech. Rep. No. I , Report Coulson, D. M., Stanford Res. Inst., Tech. Rep. No. 11, Report No. 5 , 1961. Lovelock, J. E., and Lipsky, S. K., J . Amer. Chem. SOC., 1960, 82, 431. Lovelock, J . E., Analyt. Chem., 1961, 33, 162. -_ , Nature, 1961, 189, 729. Lovelock, J . E., Zlatkis, A., and Becker, R. S., Ibid., 1962, 193, 540. Clark, S. J., in Gunther, F. h., op. cit., Volume 5, 1964, p. 32. Moore, A. D., J . Econ. E n t . , 1962, 55, 271. Lovelock, J . E., Analyt.Chem., 1963, 35, 474. Landowne, R. A., and Lipsky, S. K., Ibid., 1962, 34, 726. Dimick, K. P., and Hartmann, H., in Gunther, F. A., op. cit., I’olume 4, 1963, p. 150. Burke, J., and Giuffrida, L., J . A s s . Off. Agric. Chem., 1964, 47, 326. Phillips, D. D., Pollard, G. E., and Soloway, S. B., J . Agric. Fd Chem.,. 1962, 10, 217. Cremer, E., Kraus, T., and Bechtold, E., Chem.-Ing.-Tech., 1961, 33, 632. Gonlden, K., Goodwin, E. S . , and Davies, I,., Analyst, 1963, 88, 951. Monlrman, J . T,., and l>ubois, L., in Socbels, H. J . , JITall, R. F., and Urenncr, S., Editors, “Gas Gunther, F. A., Rlinn, R. C., and Ott, D. E., Annlyt. Chew., 1962, 34, 302. Sternbcrg, J . C., Paper presented at the 13th Pittsbiirgh Conference on Analytical Chemistry and Johns, T., Paper presented at the 14th Pittsburgh Confvrence on Analytical Chemistry and Applied Johns, T., and Braithwaite, C.H., jun., in Gunther, F. A,, op. rit., Volume 5, 1964, p. 45. Coulson, D. &I., J . Gas Chromat., 1965, 3, 134. Beckman, H., and Bcvcnue, 4., J . Clzro~nat., 1963, 10, 231. Gunther, F. 4., Barklcy, J . H., Blinn, K. C., and Ott, D. E., Stanford Res. Inst., Pesticide Res. de Faubert Maundcr, M. J., Egan, H., and Roburn, J . , AnaZyst, 1964, 89, 157. Mcnn, J . J., Patchett, G. G., and Batchelder, G. H., in Zweig, G., op. cit., Volume 2, p. 545. Goulden, R., Goodwin, E. S., and Davies, L., Analyst, 1963, 88, 941. Gunther, F. A., Blinn, R. C., and Kohn, G. K., Nature, 1962, 193, 573. Bohcmen, J . , Langer, S. H., Perrett, R. H., and Purnell, J . H., J .Clzein. SOL., 1960, 2444. Minyard, J . P., and Jackson, E. R., J . Ass. OH. Agrir. Chem., 1963, 46, 843. Watts, J . O., and Iilein, A. I<., Ibid., 1962, 45, 102. Beckman, H. F., and Bevenue, A . , J . Chromat., 1963, 12, 109. Bevenue. A.. in Zweig. G.. o B . cit.. Volume 1. D. 210. 19, 51. lishers Inc., New York and London, 1955, p. 248. 8, 399. 1961. worths, London, 1958, p. 361. No. 12, 1960. No. 3, 1960. Chromatography,” iicadcmic Press Tnc., Sew York, 1961, p. 333. Applicd Spectroscopy-, 1962. Spectroscopy, lB63. Bull., 1962, 2, No. 2.March, 19661 CHLORINATED INSECTICIDES AND ACARICIDES 173 139. 140. 141. 142. 143. 144. 145. 146. 147. 148. 140. 150. 151. 152. 153. 154. 153. 156. 157. 158. 159. 160. 161. 162. 163. 164. 165. 166. 167. 168. 169. 170.171. 172. 173. 174. 176. 176. 177. 178. 179. 180. 181. 182. 183. 184. 186. 186. 187. 188. 189. 190. 191. 192. 193. 194. 195. 196. 197. 198. 199. 200. 201. 202. 203. 204. 205. 206. 207. Robinson, J . , and Richardson, A., Chenz. & I f i d . , 1063, 1460. Bonelli, E. J., Hartmann, H., and Dimick, I<. P., J . Agric. F d Chem., 1964, 12, 333, Klein, 11. I<., and IYatts, J . O., J . A s s . Off. A g r i c . Cheni., 1964, 47, 311. Segal, H. S., and Sutherland, M. L., in Gunther, F. *4., op. c i f . , Volume 5, 1964, p. 73. Ebing, ITr., and Henkel, H. G., J . Gas Chronzat., 1964, 2, 207. Henkel, H. G., and Ebing, If-., Ibid., 1964, 2, 215. Hannon, C. I., Angclini, J., and ivalford, R., I b i d . , 1963, 1, 7, 27. Benfield, C. A., and Chilwull, E. D., rl?iuZyst, 1964, 89, 475.Burke, J., J. A s s . Ojf. Agrir. Chew., 1963, 46, 198. Taylor, M. P., J . Chronzat., 1963, 9, 28. Shoemakc, G. R., Lovelock, J . E., and Zlatkis, A., Ibid., 1963, 12, 314. Scott, K. P. IT:., and Grant, L). M", ,d~iuIysf, 1964, 89, 170. Franc, J., arid Pulichajlova, S., J . Chvoniut., 1963, 12, 22. Klein, A. K., Watts, J. O., and namico, J . X., J . A s s . Ofl. Agric. Chenz., 1963, 46, 165. Beckman, H. F., and Rerkcnkotter, P., Awalyt. Chem., 1963, 35, 242. Kalls, J . \Y., Ibid., 1960, 32, 332. Beroza, M., and Acree, F., jiin., J . z4s.s. Ofl. .4gric. Chew., 1964, 47, 1. Beroza, &I., and Sarmiento, K., ,4iiaEyt. Chewz., 1!)64, 36, 1744. RIinyard, J . P., and Jackson, E. R., J . i l g r i c . Fd Chew., 1965, 13, 50. Franc, J . , and Iiolouskova, \'., J.Chrotmt., 1965, 17, 221. Grou, E., and Balif, G., Ilevln'. Chinz., 1962, 13, 682. Schmitt, K. A., in Zweig, G., op. cit., I'olume 1, p. 281. Guinn, V. P., and Schmitt, R. -I., in Gunther, F. A,, op. cit., Volume 5, 196.1, p. 148. Gajan, K. J . , i n Gunther, P. X., op. rzt., \-oliimc 5, 1964, p. 80; Volumc 6, 1964, p. 75. Brazcc, R. D., Trans. Anter. SOC. Agrir. E ~ g r s , 1963, 6, 163. Gajan, R. J., and Link, J . , J . - 4 s ~ . Off. Agric. Chew., 1964, 47, 1119. ., Iloczn. Claewz., 1952, 26, 281. ., and Krzenminska, A . , Cheinia AnaZit., 1960, 5, 611. Fehcr, F., and Monien, H., %. AwuZyt. Chent., 1964, 204, 19. Davidek, J . , and Janicek, G., Ibid., 1963, 194, 431. Fukami, H., Kimura, H., and Nakazima, JI., Boty~i-Kujukz4, 1953, 18, 51; Chenz. Abstr., 1953, Iieller, H., Hochweber, M., and Halban, H., Helv.Clzinz. A c t u , 1946, 29, 512. Davidek, J., and Janicck, G., Experientia, 1961, 17, 473. Swineyoel, 0. A., J. S. Afr. Chenz. Iizst., 1962, 15, 88. liosmatyi, E. S., Klzina. Sredstva. Zaslz. Rust., 1963, 134; Cheni. Abstr., 1965, 62, 4518. Kosmatyi, E. S., and Shlyapak, S. I., Vop. Pitan., 1963, 22, 83; Chem. Abstr., 1964, 60, 1035. Needham, f'. H., Anulyst, 1960, 85, 792. Dewey, J. E., J . A g r i c . F d Cheun., 1958, 6, 274. Sun, Y. P., in Zweig, G., op. cit., Volume 1, p. 399. Phillips, 1%'. F., in Zweig, G., op. cit., Volume 1, p. 471. Bass, RI. H., and Make, G. H., J . Econ. E?zt., 1964, 57, 665. McDonald, S., Caw. J. Zool., 1962, 40, 719. Davidow, B., and Sabatino, F. J,, J . Ass. 08. Agric. Cliewt., 1954, 37, 902.Dewey, J . E., and Parker, B. L., J. ECOX Etat., 1964, 57, 821. Gerolt, P., Bull. Ent. Res., 1957, 48, 311. Phillips, IV. F., Bowman, M. C., and Schultheisz, K. J., J . Agric. F d Chenz., 1962, 10, 487. Earle, N. W., Pankaskie, J . E., and Sun, Y. P., J . A s s . Uff. A g r i c . ChewL., 1959, 42, 586. Mulla, M. S., Axelrod, H., and Isaak, L. 1V., ;Ilosqiiito News, 1961, 21, 21.6. Henncbcrry, T. J . , hIcGovern, \V. L., Yeomans, A. € I . , and Mason, H. C., J. Econ. E+it., 1964, Sun, Y. P., and Sun, J . Y., Ibid., 1952, 45, 26. Laug, E. P., J . Pharmac. Exp. Ther., 1948, 93, 277. Edwards, C. A., Beck, S. D., arid Lichtenstein, E, P., J . Ecoii. E n t . , 1957, 50, 622. Sun, Y. l'., and Sanjean, J., I b i d . , 1961, 54, 841. Harwood, K. I?., and Xrcckul, S., Science, 1060, 131, 1369.Bombosch, S., 11Idt. b i d . Ruiidiist. Ld-it. Forstw., Uerlitt, 1956, 85, 113. liiigemagi, U., and Terriere, L. C., J . Ecoii. E d . , 1963, 56, 343. Blinn, R. C., and Gunther, F. A , , i,iz Gunther, F. A . , op. c i f . , I.'olume 2, 1063, p. 99. Bruce, li. H., in Zweig, G., op. cat., Volume 1, p, 149. Frehse, H., Hofclzeizbr. Buyer PjlSchzttz-Nachr., 1963, 16, 182. Hlinn, R. C., Gunther, F. X., and Mulla, RI. S., J . Econ. Ent., 1960, 53, 1129. Johns, T., and Uraithwaite, C. H., zit Gunther, F. -4., op. cit., Volume 5, 1964, p. 45. lireuger, H. ti., and Volkmann, I-I., %. Phys., 1963, 173, 78. Chcn, J . Y. T., J . A s . Off. A g r i c . Chem., 1965, 48, 380. Sparagana, M., and Mason, IT;. B., Analyt. Chewa., 1962, 34, 242.Giuffrida, L., J. A s s . 08. A g r i c . Client., 1965, 48, 364. MacDougall, D., i+t Gunthcr, F. A,, op. cit., Volume 5, 1964, p. 119; and in Zweig, G., op. czt., Hornstein, I., J . Agric. F d Chew.., 1958, 6, 32. McKinley, W'. P., and llahon, J. H., J . A s s . Off. Agric. C'kem., 1959, 42, 725. Moynihan, P., and O'Colla, P., Chem. 6- I n d . , 1951, 407. 47, 9180. 57, 769. Volume 1, p. 167.174 BEYNON AND ELGAR: ANALYSIS FOR RESIDUES OF [A%a&St, VOl. 91 San Antonio, J. P., J . Ass. Off. Agric. Chem., 1960, 43, 721. Egan, H., and Evans, W. H., Paper presented at the 18th International Congress of Pure and Evans, W. H., Analyst, 1962, 87, 569. Block, R. J., Durrum, E. L., and Zweig, G., “A Manual of Paper Chromatography and Paper Electrophoresis,” Academic Press, New York, 1958.Zweig, G., Chromat. Rev., 1964, 6, 110. McKinley, W. P., in Zweig, G., op. cit., Volume 1, p. 227. Mitchell, L. C., J . Ass. Ofl. Agric. Chem., 1952, 35, 920. -, Ibid., 1953, 36, 1183. -, Ibid., 1954, 37, 530. -, Ibid., 1954, 37, 996. -, Ibid., 1956, 39, 484. -, Ibid., 1956, 39, 891. -, Ibid., 1957, 40, 294. -, Ibid., 1957, 40, 1034. --, Ibid., 1958, 41, 781. -, and Mills, P. A., Ibid., 1960, 43, 748. Mitchell, L. C., Ibid., 1962, 45, 682. ---, Ibid., 1963, 46, 988. Graham, S. O., Science, 1963, 139, 835. Krzeminski, L. F., and Landmann, W. A., J . Chromat.. 1963, 10, 515. Conkin, R. A., in Gunther, F. A., op. cit., Volume 6, 1964, p. 136. Ganshert, H., Waldi, D., and Stahl, E., in Stahl, E., Editor, “Thin Layer Chromatography,” Walker, K.C., and Reroza, M., J . Ass. Off. Agric. Chem., 1963, 46, 250. Kovacs, M. F., Ibid., 1963, 46, 884. Morley, H. V., and Chiba, M., Ibid., 1964, 47, 306. Abbott, D. C., Egan, H., and Thomson, J., J . Chromat., 1964, 16, 481. Yamamura, J., Chiba, &I., Obara, S., and Suzuki, S., Kagaku Keisatsu Kenkyaisho Hokoku, 1962, Wood, T., Nature, 1955, 176, 175. Petrowitz, H. J . , Chemikerzeitung, 1961, 85, 867. Katz, D., J. Chromat., 1964, 15, 269. Salo, T., Salminen, I<., and Fiskari, K., 2. Lebensmittel unters. u.-Forsch., 1962, 117, 369; Chem. Baumler, J., and Rippstein, S., Helv. Chim. A d a , 1961, 44, 1162. Kawashiro, I., and Hosogai, Y., Shokuhin Eiseigaku Zasshi, 1964, 5, 54; Chern. Abstr., 1964, Purdy, S. J., and Truter, E. V., Lab. Pract., 1964, 500; Analyst, 1962, 87, 802.Truter, E. V., “Thin Film Chromatography,” Cleaver-Hulme Press, 1963. Major, A., and Barry, H. C., J . A s s . Off. Agric. Chem., 1960, 44, 202. Fisher, R., Parson, I)., and Morrison, G., Nature, 1948, 161, 764. Ryhage, R., Analyt. Chem., 1964, 36, 759. Kaufman, C. W., and Jackson, H. W., Proc. 16th Int. Dairy Congr., Copenhagen, 1962, Section C, Wells, C. E., Bureau By-Lines (published by the U.S. Department of Health, Education and Lichtenstein, E. P., and Schulz, K. K., J . Agric. Fd Chem., 1965, 13, 57. Lichtenstein, E. P., Myrdal, G. R., and Schulz, K. R., Ibid., 1965, 13, 126. Stewart, D. K. R., Chisholm, D., and Fox, C. J . S., Can. J. PI. Sci., 1965, 45, 72. Uecker, G. C., Bruce, 137. N., and Bigger, J . H., J . Econ. Ent., 1965, 58, 266.Hascoet, M., and Adam, N., Phytiat.-Phytopharm., 1964, 13, 59. Henderson, J . L., in Gunthcr, F. A., op. f i t . , Volume 8, 1965, p. 74. Porter, P. E., in Zweig, G., 09. cit., LTolume 2, p. 1. Gutenmann, W. H., and Lisk, D. J., J . Agric. Fd Chem., 1963, 11, 301. Williams, S., Mills, P. A., and Mcl)owell, R. E., J . Ass. Off. Agric. Chem., 1964, 47, 1124. Esselborn, \T7., and ICrebs, K. G., Pharm. Ztg ver. ApotlzekerZtg, 1982, 107, 464. Bridges, R. G., Harrison, A., and Winteringham, F. P. W., Nature, 1956, 177, 86. Cohen, S., J. Ass. Off. Agric. Chem., 1959, 42, 549. Schechter, M. S., and Hornstein, I., Analyt. Chem., 1952, 24, 544. Hornstein, I., and Sullivan, W. N., Ibid., 1953, 25, 496. Hornstein, I., J. Ass. Off. Agric. Chem., 1953, 36, 367. Klein, A. K., Ibid., 1954, 37, 576. Reith, J. I?., Chern. Weekbl., 1953, 49, 689. Hornstein, I., Analyt. Chem., 1952, 24, 1036. -, J. A,ss. Off. Agric. Chem., 1954, 37, 623. Lichtenstein, E. P., Beck, S. D., and Schulz, K. R., J . Agric. Fd Chem., 1956, 4, 936. Friestad, H. O., A d a Pharmac. Tox., 1961, 18, 351. Klein, A. I<., J . Ass. Off. Agric. Chem., 1956, 39, 700. Fujii, M., Sato, H., Tsuji, K., and Sugawara, M., Bull. Natn. Hyg. Lab., Tokyo, 1954, 72, 115; Braid, P. E., and LeBoef, J., Analyt. Chem., 1957, 29, 1625. Applied Chemistry, Montreal, August, 1961, Section C3-26, p. 262. Springer-Verlag, 1965, p. 359. 15, 321; Chem. Abstr., 1963, 58, 14635. Abstr., 1963, 57, 12957. 61, 6262. p. 560. Welfare, Food and Drug Administration), 1962, 4, 67. Chem. Abstr., 1955, 49, 6009. 208. 209. 210. 211. 212. 213. 214. 215. 216. 217. 218. 219. 220. 221. 222. 223. 224. 225. 226. 227. 228. 229. 230. 231. 232. 233. 234. 235. 236. 237. 238. 239. 240. 241. 242. 243. 244. 245. 246. 247. 248. 249. 250. 251. 252. 253. 254. 255. 256. 267. 258. 259. 260. 261. 262. 263. 264. 265. 266. 267. 268. 269. 270. 271.March, 19661 CHLORINATED INSECTICIDES AND ACARICIDES 175 272. 273. 274. 275. 276. 277. 278. 279. 280. 281. 282. 283. 284. 285. 286. 287. 288. 289. 290. 291. 292. 293. 294. 295. 296. 297. 298. 299. 300. 301. 302. 303. 304. 305. 306. 307. 308. 309. 310. 311. 312. 313. 314. 315. 316. 317. 318. 319. 320. 321. 322. 323. 324. Paulig, G., Dt. LebensmittRdsch., 1960, 56, 223. Gunther, F. A., Blinn, R. C., and Barnes, M. M., J . Agric. F d Chem., 1957, 5, 198. Higgons, D. J., and Iiilbey, D. W., Chem. & I n d . , 1954, 1359; J . Sci. F d Agric., 1955, 6, 441. Bowery, T. G., in Zwcig, G., op. cat., Volume 2, p. 49. Kutschinski, A. H., and Luce, E. N., Analyt. Chem., 1952, 24, 1188. Erwin, W., Paper presented at the 1st Annual Meeting of the Pacific Branch, Entomological Beckman, H., and Bevenue, A,, J . Agric. F d Chem., 1964, 12, 183. Harris, H. J., Ibzd., 1955, 3, 939. Margot, A., and Stammbach, K., in Zweig, G., op. cit., Volume 2, p. 65. Blinn, R. C., Gunther, F. A., and Kolbezen, M. J., J . Agric. F d Chem., 1954,2, 1080. \\'heatley, G. A., Aqzn. Appl. Biol., 1965, 55, 325. Grzenda, A. R., Nicholson, H. P., Teasley, J . I., and Patric, J . H., J . Econ. Ent., 1964, 57, 616. Coulson, D. M., Sta9zford Res. Inst., Pesticide Res. Bull., 1962, 2, No. 4, p. 1. Lipke, H., and Chalkley, J., Bull. W l d Hlth Org., 1964, 30, 57. Hunter, C. G., Robinson, J., and Richardson, A., Brit. Med. J . , 1963, 221. Dale, 11:. E., and Quinby, G. E., Science, 1963, 142, 593. Hayes, IV. J., Dale, W. E., and Le Breton, R., Nature, 1963, 199, 1189. Williams, S., J . A s s . Off. Agrac. Chem., 1964, 47, 815. Miskus, R., in Zweig, G., op. cit., Volume 2, p. 97. Rosenthal, I., Frisone, G. J., and Gunther, F. A., J . Agric. F d Chem., 1957, 5, 514. Gordon, C. F., Haines, L. D., and Martin, J . J., Ibid., 1963, 11, 84. Gordon, C. F., and Schuckert, K. J., in Zweig, G., op. cit., Volume 2, p. 263. Zweig, G., Pye, E. L., and Peoples, S . George, D. A., Fahey, J . E., and Walker, I<. C., Ibid., 1961, 9, 264. Hughes, J. T., Analyst, 1961, 86, 756. Eiduson, H. P., J . A s s . 08. Agric. Chem., 1961, 44, 183. Gunther, F. A., and Blinn, R. C., J . Agric. F d Chem., 1957, 5, 517. Cueto, C., jun., and Hayes, W. J., jun., Ibid., 1962, 10, 366. Roburn, J., Chenz. & Ind., 1963, 1555. Korte, F., Ludwig, G., and Vogel, J., Justus Liebigs A n n l n Chem., 1962, 656, 135. Ludwig, G., Wies, J., and Korte, F., L i f e Sciences, 1964, 3, 123. Hardee, D. D., Gutenmann, W. H., Lisk, D. J., Gyrisco, G. G., and Edmonds, C. M., J . Econ. Ent. Morley, H. V., and Chiba, M., Can. J . PI. Sci., 1965, 45, 209. Harvey, H. E., and Harvey, W. E., N. 2. J . Sci., 1963, 6, 3. Porter, P. E., in Zweig, G., op. cit., Volume 2, p. 143. Barnes, W. W., and Ware, G. W., J . Econ. E n t . , 1965, 58, 286. Cassil, C. C., and Drummond, P. E., Ibid., 1965, 58, 356. Graham, J . R., Yaffe, J., Archer, T. E., and Bevenue, A., in Zweig, G., op. cit., Volume 2, p. 507. Terranova, A. C., and Ware, G. W., J . Econ. Ent., 1963, 56, 596. Terriere, L. C., in Zweig, G., op. cit., Volume 2, p. 209. Rusk, H. W., and Fahey, J. E., J. Agric. F d Chern., 1961, 9, 263. Hardee, D. D., Gutenmann, 11'. H., Kennan, G. I., Gyrisco, G. G., Lisk, D. J., Fox, F. H., Trim- berger, G. W., and Holland, R. F., J . Econ. E n t . , 1964, 57, 404. Bowery, T. G., in Zweig, G., op. cit., Volume 2, p. 245. Lowen, W, K., Cluett, M. L., and Pease, H. L., in Zweig, G., op. cit., Volume 2, p. 303. Cluett, M. L., Lowen, W. I<., Pease, H. L., and Woodhouse, C. A., J . Agric. F d Chem., 1960, 8, 277. Gunther, F. A,, and Blinn, R. C., 09. cit., p. 337. Fullmer, 0. H., and Cassil, C. C., J . Agric. Fd Chem., 1958, 6, 906. Cassil, C. C., and Yaffe, J., in Zweig, G., 09. cit., Volume 2, p. 473. Gunther, F. A., Blinn, R. C., and Rarklcy, J . H., J . Agric. F d Chem., 1959, 7, 104. Graupner, ,4. J., and Dunn, C . T,., Ibid., 1960, 8, 286. Dunn, C. L., in Zweig, G., 09. cit., Volume 2, p. 623. Nicolov, N. F., and Doncv, L., Z h . Analit. Khim., 1963, 18, 532. Witt, J. M., Bagatella, G. F., and Percious, J. K., Stanford lies. Inst., Pesticide Res. Bull., 1962, Received August 24th, 1965 Society of America, Lake Tahoe, California, 1953. J . Agric. Fd Chem., 1963, 11, 72. 1964, 57, 583. 2, No. 1.

ISSN:0003-2654    

DOI:10.1039/AN9669100143

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

176 BASSETT AND JONES : SPECTROPHOTOMETRIC DETERMINATION [AndySt, VOl. 91 Spectrophotometric Determination of 0.01 to 0.1 per cent. of Antimony in Lead BY J. BASSETT AND J. C. H. JONES (Chemistry Department, Woolwich Polytechnic, London, S.E. 18) The development of a spectrophotometric method for the determination of small amounts (0.01 to 0.1 per cent.) of antimony in lead is described. The proposed method is based on the extraction of antimony from hydro- chloric acid solution with di-isopropyl ether, followed by spectrophotometric determination with the iodide procedure. The presence of other impurity elements usually found in lead causes no significant interference. CERTAIN physical and chemical properties of lead such as the rate of oxidation,l fatigue resistance,2 and grain size3 are influenced by the presence of small amounts of antimony. It is therefore important to have a method for determining antimony (0.01 to 0-1 per cent.) in lead that is suitable for routine use in a laboratory.Many methods have been reported in which lead is separated as lead sulphate and the antimony subsequently determined, either polarographically4p5s6 or spectrophotometrically.7 These methods are not however completely satisfactory as we have confirmed in our investi- gations that an appreciable amount of antimony may be adsorbed on the lead sulphate precipitate. The object of the present investigation was to devise a more effective separation of antimony from lead, and to determine the antimony spectrophotometrically or polaro- graphically.Ward and Lakins and o t h e r ~ ~ ~ l ~ ~ ~ ~ have reported satisfactory extraction of antimony(v) from hydrochloric acid solution with di-isopropyl ether, while Van Aman and co-workers12 have drawn attention to the importance of the order in which the reagents are added. They found that, in order to obtain maximum extraction of antimony, the di-isopropyl ether should be added to the concentrated hydrochloric acid solution before diluting the solution with water. In the preliminary experimental work, the applicability of this solvent extraction procedure to the determination of antimony in lead was investigated by using polarographic and spectrophotometric techniques. The base electrolytes used in the polarographic studies were sulphuric acid solution,l3 phosphoric acid solution14 and a mixture of hydrochloric acid and potassium bromide.l5 Results were low, possibly due to loss of antimony during its extraction from the organic phase into the base electrolyte. A spectrophotometric method12 with Rhodamine B was examined, the antimony being determined directly in the organic extract. This procedure was found satisfactory when applied to hydrochloric acid solutions containing antimony only, but failed to give repro- ducible results for antimony in lead. The second spectrophotometric method examined was that described by McChesney,lG in which the antimony is converted to the yellow iodo-antimonate ion. The method was applied to the solution obtained by evaporating the organic extract with sulphuric acid. Satisfactory results were obtained.The separation of antimony by co-precipitation on ferric hydroxide and manganese dioxide was also studied in conjunction with the iodide method of McChesney. Although fairly satisfactory results were obtained, neither procedure was as rapid and convenient as the solvent extraction method. It was concluded that, of the methods studied, the most satisfactory to be adopted as a routine procedure for determining small amounts of antimony in lead, was extraction with di-isopropyl ether followed by spectrophotometric determination as the iodide. METHOD APPARATUS- A Hilger Uvispek spectrophotometer was used for all the optical-density measurements.March, 19661 OF SMALL AMOUNTS OF ANTIMONY I N LEAD 177 REAGENTS- All reagents should be of analytical-reagent grade.Hydrochloric acid, concentrated, sp.gr. 1.18. Hydrochloric acid - bromine mixture-Shake 25 ml of bromine with 2.5 litres of hydro- Ceric sulphate solution-Dissolve 0.2 g of ceric sulphate in 100 ml of 0.1 N sulphuric acid. Di-isopropyl ether. Wash solution-Shake 60 ml of hydrochloric acid with 20 ml of di-isopropyl ether and Sulphuric acid, 50 per cent. v / v , aqueous-Prepare from sulphuric acid, sp.gr. 1.84. Sulphuric acid, 5 per cent. v / v , aqueous-Prepare from 50 per cent. v/v aqueous sulphuric Potassium iodide - ascorbic acid reagent-Dissolve 56.0 g of potassium iodide and 10 g Standard antimony solution A-Dissolve 0.6688 g of antimony potassium tartrate, chloric acid. 28 ml of water. Separate the two layers and retain the aqueous layer. acid.of ascorbic acid in 500ml of water. previously dried a t 100" C, in 500 ml of water. 1 ml = 0.0005 g of Sb. 1 ml = 0.0001 g of Sb (= 0-01 per cent. on 1-g lead sample). Standard antimopzy solution 23-Dilute 20 ml of solution A to 100 ml. PROCEDURE- Dissolve the sample (1 g for 0.01 to 0.05 per cent. of antimony, or 0.50 g for 0.05 to 0.1 per cent. of antimony) in a mixture of 50 ml of concentrated hydrochloric acid and 10 ml of hydrochloric acid -bromine solution. It is essential that the solution is not boiled a t this stage but only warmed. (If the lead sample is rolled out as thin foil of thickness approxi- mately 0.0015 inch, it will dissolve in about 20 minutes.) When dissolution is complete, cool the solution, add 1 ml of ceric sulphate solution to ensure that all of the antimony is converted to the pentavalent state.Transfer the solution to a separating funnel and make up the volume to 120 ml with concentrated hydrochloric acid. Shake the solution for 1 minute. Add 40ml of di-isopropyl ether and shake the solution for a further minute before cooling. Introduce 56ml of water into the separating funnel and shake the solution for a further period of 1 minute to extract antimony(v) into the ether layer. Cool the solution and separate the two layers. Carry out a second extraction on the aqueous layer by adding 1 ml of ceric sulphate solution, 40 ml of di-isopropyl ether and shaking the solution for 1 minute. Separate the two layers. To the combined organic extracts add 5 ml of wash solution and, after shaking, separate the organic layer and place it in a 250-ml beaker.Introduce 20 ml of 5 per cent. v/v sulphuric acid and place the beaker on a steam-bath. When the organic solvent has been removed add to the solution 6.6 ml of 50 per cent. v/v sulphuric acid. Cool the solution, add to it 25 ml of the potassium iodide - ascorbic acid reagent, filter it into a 50-ml graduated flask and dilute to the mark with water. Measure the optical density of the solution after 5 minutes in a 2-cm cell against water at a wavelength of 425mp. CALIBRATION- Transfer 1-0, 2.0, 4.0, 6.0, 8-0 and 10-ml portions of standard antimony solution B into 50-ml graduated flasks. Add to each flask 8.6 ml of 50 per cent. v/v sulphuric acid, 25 ml of potassium iodide - ascorbic acid reagent and dilute to the mark with water.Mix the solutions thoroughly and measure their optical densities after 5 minutes in a 2-cm cell against water at 425 mp. Deduct the optical density of a reagent blank solution. Prepare a calibration graph. Deduct the optical density of a reagent blank solution. RE s u LTS RECOVERY OF ANTIMONY IN THE PRESENCE OF LEAD- The procedure was studied by using 1 g of high-purity lead to which was added a known volume of standard antimony solution consisting of pure antimony dissolved in concentrated hydrochloric acid. The antimony solution was added before the hydrochloric acid - bromine178 BASSETT AND JONES : SPECTROPHOTOMETRIC DETERMINATION [ A ndySt, VOl. 91 mixture, as it was found that the presence of antimony increased the rate of dissolution of the lead.Some typical results are shown in Table I. TABLE I RECOVERY OF ANTIMONY IN THE PRESENCE OF LEAD Antimony added, per cent. 0~000 0.010 0.020 0.030 0.030 0*050 0.050 0.060 0.070 0.080 0.100 0.100 Antimony found, per cent. o*ooo 0.010 0.01 i 0.030 0.030 0.050 0.050 0.057 0.066 0.Oi 1 0.089 0.086 Error, per cent. 0 0 - 15 0 0 0 0 -5 - 6 - 11 - 11 - 14 DETERMINATION OF ANTIMONY I N THE PRESENCE OF OTHER ELEMEXTS- The method was studied in the presence of various elements that normally occur with lead. The results obtained are shown in Table 11. TABLE I1 DETERMINATION OF ANTIMONY IK THE PRESENCE OF OTHER ELEMENTS Impurity added 0.050q6 Cadmium 0.0400/, Bismuth 0.0500/, Nickel 0.050% Zinc 0.050% Arsenic 0.050% Tin 0.0647& Copper 0.0500,b Iron 0-05Oq; Tellurium 0.0500,, Selenium Form of .4ntimony added, Antimony found, Error, added impurity per cent.per cent. per cent. Cadmium chloride Lead sample containing 0-040y6 of bismuth Nickel chloride Zinc chloride Lead sample containing 0.050/, of arsenic Lead sample containing 0.05'36 of tin Lead sample containing 0.0649/0 of copper Ferric chloride Tellurium dissolvcd in nitric Sclcnium dissolved in nitric acid acid 0.030 0.030 0-030 0-030 0.030 0.030 0.030 0.030 0.030 0.030 Lcad sample containing only bismuth, copper 0.030 and silver 0.03 1 0.028 0.027 0.027 0.028 0.03 Z 0.028 0-032 0.030 0.032 0.03 1 TABLE I11 REPRODUCIBILITY OF THE METHOD WITH 0-03 PER CENT. ANTIMONY ADDED TO 1-g LEAD SAMPLES Antimony found, per cent. . . 0.028 0.027 0.030 0.027 0.030 Deviation .. . . . . 0.002 0.003 0.000 0.003 0.000 0.032 0.029 0-031 0.033 0.031 0.027 0.002 0.001 0.001 0.003 0.001 0.003 Mean = 0.030. Mean deviation = 0.002. Relative mean deviation = o'oo2 loo- = 6.7 per cent. 0.030 Standard deviation = 0.002. $ 3 - 7 - 10 - 10 - 7 + 3 - 7 $ 7 0 + 7 f 3March, 19661 OF SMALL AMOUNTS OF ANTIMONY I N LEAD 179 PRECISION OF METHOD- The reproducibility of the method was investigated with l-g samples of high-purity lead, to which the equivalent of 0.030 per cent. of antimony was added as a known volume of standard antimony solution. The results are given in Table 111. DISC~JSSION The method was found satisfactory when using a l-g lead sample containing the equivalent of 0.01 to 0.05 per cent. of antimony (see Table I). At the higher concentration range, 0.05 to 0.10 per cent., the recoveries of antimony are, however, slightly low.It is therefore recommended that when determining amounts of antimony greater than 0.050 per cent. a smaller sample should be taken so that the concentration of antimony is within the limits giving quantitative recovery. It is not possible to extend the range below 0.01 per cent. of antimony by taking more than 1 g of sample, because of the difficulty in dissolving the larger amount of lead. According to McChesney,16 only bismuth, which itself gives a colour with potassium iodide, is likely to interfere in the spectrophotometric determination of antimony by the iodide method. It was found that the di-isopropyl ether extraction separated antimony from bismuth and so eliminated this interference.No serious interference was observed from other elements investigated (see Table I I). We thank Dr. A. I. Vogel, Head of the Chemistry Department of the Woolwich Poly- technic for his interest, and one of us (J.C.H. J,) wishes to thank the Directors of Associated Lead Manufacturers for enabling him to undertake the present research. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. REFERENCES Green, F. A., “The Refining of Non-ferrous RIetals,” The Institute of Mining and Metallurgy, If’aterhouse, H., “The Fatigue Resistance of Lead,” B.S.F.R.-I. Research lieport -4440, 1937. Butler, J. M., J . Inst. Metals, 1957-58, 86, 145. Cozzi, D., Analytica Chzm. Acta, 1950, 4, 204. Zotta, RI., Gazz. Chim. Ital., 1948, 78, 143. Athavale, IT. T., Dhaneshwar, K. G., Mehta, ?IT. M., and Sundaresan, RI., Analyst, 1961, 86, 399. Luke, C. L., Analyt. Chem., 1953, 25, 674. Ward, F. N., and Lakin, H. W., Analyt. Chem., 1954, 26, 1168. Edwards, F., and Voigt, A. F., Ibid., 1949, 21, 1204. Bonner, N. A., J . Anzer. Chem. SOC., 1949, 71, 3909. Schweitzer, G. I<., and Storms, L. E., Analvtica Chim. Acta, 1958, 19, 159. Van Aman, R. E., Hollibaugh, F. D., and Kanzelmeyer, J. H., Analjit. Chem., 1959, 31, 1783. Lingane, J. J., Ind. Engng Chem., Analyt. Edn, 1943, 15, 583. Meites, L., “Polarographic Techniques,” Interscience Publishers Inc., New York, 1955, 261. Kolthoff, I. TI., and Probst, K. I-., Analyt. Chem., 1949, 21, 753. McChesney, E. W., Ind. Engng Chem., Analyt. Edn, 1946, 18, 146. London, 1950, 290. Received J u n e 15th, 1965

ISSN:0003-2654    

DOI:10.1039/AN9669100176

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

180 BANHAM et al. : GERMANIUM DIODES FOR GAMMA-SPECTROMETRIC [Analyst, Vol. 91 The Use of Lithium-drifted Germanium Diodes for the -spectrometric Determination of Radioactive Fission-product Nuclides BY M. F. BANHAM, A. J. FUDGE AND J. H. HOWES (Chemistry and Electronics Divisions, U. K. Atomic Energy Research Establishment, Harwell, Didcot, Berks.) The superiority of a y-spectrometer incorporating a germanium - lithium diode detector and field-eff ect transistor head amplifier over the conventional sodium iodide - thallium system, for the resolution of most of the difficult determinations encountered in fission-product radiochemistry, is demonstrated. DURING the past 6 years, semiconductor solid-state detectors have become generally available for the detection of heavy charged particles.Lately, the discovery of the lithium drift- process, first in silicon1 and then in germanium,2 has led to the publication of several papers on their use, initially for conversion electron investigations and most recently for y-spectro- metry.3s4s6 Because of its higher atomic number germanium has a much better photo-electric response than silicon, and is therefore a much more attractive detector for y-spectrometry, particularly in the region up to about 1.5 MeV. In the drift process, lithium is diffused to depths of several millimetres in a piece of p-type germanium to produce a layer of n+-type material, a central layer of intrinsic material and a layer of the original p-type germanium. The whole makes a p-i-n detector. Incident y-radiation is absorbed by photo-electric or Compton processes, and the ions produced are collected by means of a potential difference applied across the detector.Lithium ions are highly mobile at normal temperatures and so, to achieve stability and a low noise level in the detector, it must be operated at low temperatures. It is usual to mount the detector in a cryostat operated at liquid-nitrogen temperature (77" K). y-Spectrometry is one of the most useful techniques available to radiochemists for the analysis of mixed fission products in irradiated nuclear fuel specimens. However, the best sodium iodide detector has a resolution of not less than 50 keV (the full width of the photopeak at half maximum height) a t 662 keV (caesium-137). This has been inadequate for the determination of some individual nuclides in fission-product mixtures.Several difficult problems in fission-product analysis have been overcome by radio- chemical separation, or where this is not possible, by mathematical analysis of the y-spectrum. There are, in particular, four instances where an improvement in resolution, such as is claimed for lithium-drifted germanium diodes, would enable direct measurement of the activities to be made. These determinations are as follows- (a) zirconium-95 in the presence of niobium-95 daughter, (b) ruthenium-106 in the presence of ruthenium-103, (c) caesium-137 in the presence of caesium-134, ( d ) cerium-144 in the presence of cerium-141. The three fission-product nuclides most frequently used for the determination of burn-up (the total number of fissions) of irradiated nuclear fuel specimens are zirconium-95, caesium-137 and cerium-144.A preliminary investigation has been carried out to test the feasibility of using the high resolving power of a germanium - lithium detector for the determination of these nuclides in mixed fission products, with a view to extending its application to non- destructive y-scanning of nuclear fuel. The results of the first experiments are presented in this paper.March, 19661 DETERMINATION OF RADIOACTIVE FISSION-PRODUCT NUCLIDES 181 EXPERIMENTAL APPARATUS- The apparatus used for this experimental work is standard Hanvell2000 series equipment, with the exception of the head amplifier and distribution unit which are experimental and the subject of another paper.6 The schematic layout is shown in Fig.1. The input stage of Main Distribution Head unit amplifier amplifier 2153 A Cooled with ~~;~~~~~ Pulse-height Print-out jTH--t-iil analyzer unit 45 germanium detector FiFl generator Fig. 1. Schematic diagram of y-spectrometer the amplifier is an n-channel field-effect transistor* which is cooled to about 100" K together with the detector, a lithium-drifted germanium crystal, as shown in Fig. 2. The germanium detector is located on a copper rod which is immersed in liquid nitrogen, and the input stage of the head amplifier is in close proximity with the detector. The source is placed directly on the cold chamber envelope if suitable. F 7- /I H A = Liquid nitrogen B = Base plate C = Head amplifier D = Thermocouple E = Multiway cable F = Field-effect transistor G = Lid H = Vent I = Lid core j = Lid seal K = Cold chamber L = Crystal M = Platform N = Cap 0 = Tag-board assembly holding input components P = Dewar flask Q = Thermal shield R = Thermal rod S = Outer case Fig.2. Lithium-drifted germanium y-detector * Type 2N2346, made by Amelco Semiconductors Ltd., P.O. Box 1030, Mountain View, California, U.S.A.182 BANHAM et al. : GERMANIUM DIODES FOR GAMMA-SPECTROMETRIC [Analyst, Vol. 91 The advantage of operating the field-effect transistor at low temperature is that the input capacitance of the system can be reduced to a minimum by locating the input stage close to the detector. This reduction in capacitance in conjunction with lower capacity detectors can afford an improvement in resolution.A significant reduction in input noise is achieved by the fact that the thermal noise and gate leakage current noise are reduced to a minimum at this temperature. The noise performance of the head amplifier with single R.C. differentiation and integra- tion with 10-pF total input capacitance is 160 r.m.s. electronic charges. IVhen used in conjunction with a germanium - lithium detector (2 cm in diameter and 4 to 5-mm depletion depth') with a total input capacitance of 48 pF, the full width of the photopeak at half maximum value for cobalt-57 (122 keV and 136 keV) is less than 3 keV. This performance has been repeated over several months. A limitation in achieving a higher resolution is the over-all drift of the system. It has been shown that a spectrum stabiliser (type 2149) would achieve an improvement for counting periods greater than 15 minutes dependent on the over-all drift of the system.APPLICATION OF THE APPARATUS TO FISSION-PRODUCT ANALYSIS- The apparatus described above has been used to resolve the major problem of fission- product analysis, namely the interference of one nuclide with another, which conventional methods, with thallium activated sodium iodide detectors, are incapable of doing. DETERMINATION OF ZIRCONIUM-95 IN THE PRESENCE OF NIOBIUM-95- Zirconium-95 is used extensively for the determination of burn-ups in short irradiated samples. For the best results it is necessary to separate the zirconium chemically from the main interference, viz., the daughter-product niobium-95.The energies of the y-rays emitted by these two nuclides differ by only 40 keV and they are not even partially resolved by a sodium iodide detector. Zirconium-95, in fact, emits two y-rays at 724 and 756 keV, respec- tively, whereas niobium-95 emits only one y-ray at 764 keV. The spectra obtained with the conventional method (sodium iodide detector) and the lithium-difted germanium detector are shown in Fig. 3. In the spectrum obtained with the sodium iodide - thallium detector I I Fig. 3. y-Spectrum of niobium-95 + zirconium-96; curve A , sodium iodidc detector; curvc R, germanium detector only one photopeak is observed which is composed of the three photopeaks expected. These three peaks are clearly seen in the spectrum obtained with the germanium - lithium detector.The two zirconium-95 y-rays are completely resolved from each other, and the peak for niobium-95 at 764 keV is partially resolved from the peak for zirconium-95 at 756 keV. This spectrum demonstrates that it is thus possible to determine zirconium-95 in the presence of its daughter, niobium-95, without recourse to mathematical methods to calculate the proportion of each nuclide present. It is, in fact, possible to calculate the ratio of niobium-95March, 19661 DETERMIEATION OF RADIOACTIVE FISSION-PRODUCT NUCLIDES 183 to zirconium-95 from this spectrum, provided that the decay scheme is known. By using the decay scheme shown and the simple arithmetic which follows, this ratio was calculated. DECAY SCHEME OF ZIRCONIUM-% AND NIOBIUM-% 65 days MeV MeV MeV 0.764 MeV -7- Let- C, be the number of counts in the photopeak for zirconium-95 a t 724 keV, A, be the absolute abundance of the 724-keV y-ray, El be the efficiency of detection a t 724 keV.Then, if A, and E, are the corresponding absolute abundance and efficiency of detection for the 756-keV y-ray of zirconium-95, the number of counts in this photopeak, C,, is given by- If C, is the total count in the combined photopeak for zirconium-95 a t 756 keV plus niobiiim-96 a t 764 key, then the true count of the peak for niobium-96 a t 764 keV, C,, assuming that the absolute abundance of this y-ray is 100 per cent., is given by- If this photopeak is counted with an efficiency of E,, then the ratio of niobium-95 to zirconium-96 is given by- c, = c3 - c, C, x A2 x E, C, x E, R =- or The calculated value was 2-22, which compares well with the theoretical value of 2.18 for an equilibrium mixture, of which Fig.3 is the spectrum. The accuracy of this calculation is dependent on the accuracy of the decay scheme and efficiency of the detector for y-rays of different energies. MIXTURES OF RUTHEKIUM-103 AND RUTHENIUM-106- Ruthenium isotopes are rarely used as burn-up monitors although both ruthenium-103 and ruthenium-106 are potentially useful. The chemical properties of ruthenium are such that dissolution of a fuel specimen often results in the loss, by volatilisation, of an unknown amount of this element from the sample solution. Determination of the absolute amount of ruthenium is therefore of no value. However, it may still be useful to determine the ratio of ruthenium-103 to ruthenium-106 which will remain undisturbed although the total amount of ruthenium may be decreased.The fission yield of ruthenium-106 varies by a factor of more than 10 for the two fissile nuclides, uranium-235 and plutonium-239, whereas that of ruthenium-103 differs by about 2. It should be possible, therefore, to determine the relative proportions to the total number of fissions in specimens containing mixtures of184 [,4nalyst, Vol. 91 fissile nuclides, e g . , plutonium dioxide - uranium dioxide and plutonium carbide - uranium carbide fuels from the measured ratio of ruthenium-103 to ruthenium-106. Another case of interest is highly-burned-up low-enriched uranium, where significant quantities of pluton- ium-239 are produced from uranium-238 by neutron capture, and then undergo fission.BANHAM et al. : GERMANIUM DIODES FOR GAMMA-SPECTROMETRIC / I I I I - / I I I I I - / I I I I I - 1 I I I I I / I r z I 5 38 lteV L I \ \ \\A \ \ \ \ \ \ \ B ‘\ \ A50 500 550 600 650 I( Fig. 4. y-Spectrum of ruthenium-103; curve A, sodium iodide detector; curve B, germanium detector J I I / / I I I I I I / I / / --.’ -4 5 I 3 lteV I I I I 1 -150 100 550 6CO 650 I< V Fig. 5. y-Spectrum of ruthenium-106 -rho- dium-106; curve A, sodium iodide detector; curve B, germanium detector Portions of the spectra of ruthenium-103 and ruthenium-106 - rhodium-106 are shown in Figs. 4 and 5, respectively. The spectrum of a mixture of ruthenium-103 and ruthenium-106 - rhodium-106 is shown in Fig. 6.From the spectra of the pure nuclides, the ratios of the counts in the peaks for ruthenium-103 at 498 keV and 610 keV, and in the peaks for ruthen- ium-106 at 513 keV and 621 keV can be calculated. With this knowledge it is possible to determine the amount of each nuclide present in a mixture by mathematical treatment as follows- If R, is the ratio of the counts in the peak a t 498 keV to the counts in the peak for ruthcnium-103 R, is the ratio of the counts in the peak at 513 kcV to the counts in the peak for ruthenium-106 C5 is the total count in the mixed peak for ruthenium-103 a t 498 keV and ruthcnium-106 at 513 keV; C, is the total count in the mixed peak for ruthenium-103 at 610 keV and ruthenium-106 at 621 keV, then it can be derived that the number of counts due to the 498-lreV y-ray of ruthenium-103 in the mixed peak is given by- a t 610 keV; at 621 keV; 103 - R3 (C5 - c, x’ R,) From the spectrum shown in Fig.6 the value of Ci:: was calculated, and was within These values were 21,209 and 20,487, respectively. The R, - ri, c,,, - 3-5 per cent, of the expected value. ratio of ruthenium-106 to ruthenium-103 was 9.5. MIXTURES OF CAESIUM-134 AND CAESIUM-137- Caesium-137, like zirconium-95, is used extensively for the determination of burn-up, and has many advantages. One of these, its migration at relatively low temperatures, excludes its use with samples where the temperature of the sample is known to have been greater than 650” C during the irradiation. Where this is not the case, a second disadvantage may still cause severe limitation to its usefulness.Several isotopes of caesium are produced in high yield in fission, including the stable isotope caesium-133. This isotope has an appreciable neutron-capture cross-section which may be greatly enhanced under suitable reactor conditions by a very large resonance It does, however, suffer from two major disadvantages.March, 19661 DETERMINATION OF RADIOACTIVE FISSION-PRODUCT NUCLIDES 185 in its capture cross-section spectrum at about 6 eV. The product of this (n,y) reaction is caesium-134 (half-life of 2.3 years). This nuclide has a complex y-spectrum with y-rays of high abundance a t 605 keV and 796 keV that cause significant interference with the 662-keV y-ray of caesium-137 when the spectrum of a mixture is obtained by the conventional sodium iodide detector. The extent of this interference can only be determined with any degree of accuracy by involved mathematical treatment of the spectrum and it is, therefore, of interest to be able to resolve these two nuclides.Fig. 7 shows the y-spectrum of a mixture of caesium- 134 and caesium-137, in which the ratio of caesium-134 to caesium-137 is 2-75. The three peaks in question are all well separated from each other, and the determination of caesium-137 from this spectrum should present no difficulty. aJ 3 u c .- E L aJ Q VI c) K 3 0 V ' 0 3 R u Ru 3 keV 621 IkeV i I I I I I 450 500 550 600 650 I Fig. 6. y-Spectrum of mixed ruthenium- 103 and ruthenium-106 - rhodium-106 aJ 3 c u - E a L a, VI LI r 3 0 V / cs 134 106 keV , \ \ I / / ,/ 134 .cs 796 IkeV I I I 1 Pig. 7. y-Spectrum of mixed caesium-134 and cacsium-137; curve A,. sodium iodide detec- tor; curve B, germanium detector MIXTURES OF CERIUM-141 AND CERIUM-144- The two major y-active isotopes of cerium produced in fission are cerium-141 (half- life of 32 days), which emits a y-ray at 145 keV, and cerium-144 (half-life of 285 days) which emits a y-ray at 134 keV. The chemical properties of cerium-144, together with its half-life, combine to make it an attractive nuclide to use for the determination of bum-up. The presence of cerium-141 in specimens that have not been allowed to decay for long periods, however, complicates the determination to a considerable extent. It is possible to use the 2.18 MeV y-ray of its daughter praseodymium-144, which quickly reaches equilibrium with its parent cerium-144, but the low abundance of this y-ray, combined with the low efficiency of y-ray detectors at this high energy, makes its measurement difficult. Fig.8 shows the spectrum of a mixture of cerium-141 and cerium-144 obtained with a germanium - lithium detector. For comparison, spectra of the same mixture and of pure cerium-144 obtained with sodium iodide - thallium detector are also shown. The advantage of the gennanium - lithium detector over the sodium iodide - thallium detector is clearly demonstrated by the two completely resolved and almost perfectly symmetrical peaks which are obtained by this means. The resolution at 134 keV is 3.3 keV (the full width of the photopeak at half maximum height).186 BANHAM et d.: GERMANIUM DIODES FOR GAMMA-SPECTROMETRIC [AfldySt, VOl. 91 MIXED FISSION PRODUCTS- The preceding paragraphs have shown that the apparatus described is capable of resolving many of the problems in fission-product analysis that are difficult to solve by using conven- tional sodium iodide - thallium detectors. All the sources of activity used were separated chem- ically, and each contained only one interfering nuclide after separation. It would be of value to be able to resolve the nuclides of interest (zirconium-95, ruthenium-103, ruthenium-106, caes- ium-137 and cerium-144) from fission-product solutions without previous chemical separation. Three samples, representing different conditions of irradiation and decay, were examined in experiments to determine the feasibility of this approach.The spectra are shown in Figs. 9, 10 and 11. Eight peaks from isotopes of caesium, cerium, ruthenium, niobium and zirconium can be identified between 550 and 800 keV. Solutions were examined in all three cases, and the small amounts of ruthenium present resulted from the loss of this element by volatili- sation during dissolution of the specimen. In nearly all instances the photopeaks are well resolved and superimposed on a background that can be estimated with a good degree of certainty. It should therefore be possible to carry out fission-product analysis directly on fission-product solutions without any chemical separation, for a wider range of nuclides and irradiation and decay conditions than has hitherto been possible.I I I I ~ I0 120 130 140 I50 I< Fig. 8. y-Spectrum of mixed cerium-141 +- cerium-144 - praseodymium-144; curve -4, sodium iodide detector; curve B, germanium detector THE EFFICIENCY OF THE APPARATUS- 600 650 700 753 9’Nb 764 keV HOO keV Fig. 9. y-Spectrum of mixed fissicn pro- ducts; $ 2 days’ irradiation, 150 days’ decay The efficiency of the apparatus is defined by the equation- E = (% - CB:) x 100 per cent, A x D where C z is the total number of counts per second in a photopeak contained in channels m to n, CB; is the total number of counts per second background in channels m to n, A is the abundance of the y-ray in the decay scheme of the emitting nuclide, D is the disintegration rate of the source. It has been showng that the efficiency is strongly dependent on y-energy.The efficiency of the apparatus described was determined at 134 keV for cerium-144 and 662 keV for caesium-137 with standard sources. The values obtained were 0.16 per cent. and 0.0069 per cent., respectively, when the sources were placed as near to the detector as possible, i.e.,March, 19661 DETERMINATIOX OF RADIOACTIVE FISSION-PRODUCT NUCLIDES 187 directly on the cold-chamber envelope. These values are much lower, and the graph of efficiency versus energy of incident y-ray is much flatter than reported by other workers.6 These facts are probably attributable to a low geometry factor, due partly to distance and partly to the fact that the detector was inverted, thereby causing the y-rays to be incident on the back of the detector.The precision of these measurements is the same as the precision of counting, i e . , 1 per cent. on lo4 events recorded in the photopeak. The degree of accuracy, however, will be less good due to the errors in the absolute calibration of the standard sources (about 2 1 to 2 per cent.) and in the branching ratios in the decay schemes of the nuclides used (about k5 per cent.). Most of the sources used had been prepared previously for measurement on a conventional sodium iodide - thallium y-spectrometer with an efficiency of 10 per cent. at 134 keV, and were in the range 1 to 10 pC in activity. Although counting times with the germanium - lithium detector were usually 1 to 16 hours to accumulate about lo4 counts in <he principal photopeak, the apparatus, kven with this low efficiency, is great value to the radiochemist.of W c Y - 2 - E L W a Lo u C 3 0 U '06 Ru 621 keV cs 62 lteV I 3 7 95 Zr \ 1,756 keV' 695 keV 95 Nb 764 IkeV '3"s 756 keV I I I 650 700 750 800 I< Fig. 10. y-Spectrum of mixed fission pro- ducts; 193 days' irradiation, 750 days' decay W c Y - - E a - aJ Lo Y C 7 0 v 600 650 700 750 800 IkeV Fig. 11. y-Spectrum of mixed fission pro- ducts; 760 days' irradiation, 150 days' decay CONCLUSIONS An apparatus incorporating a lithium-drifted germanium detector, and designed primarily for studying low-noise amplifiers, has been used for a preliminary examination of the capabilities of this type of detector for y-spectrometry. The results presented here show that, even with poor geometry and low efficiency, the germanium - lithium detector is far superior to the best sodium iodide detector for resolving complex mixtures of y-ray emitting nuclides such as exist in fission-product mixtures. This high resolving power, coupled with the ability by electronic means to examine small parts of the y-spectrum in detail, should enable direct quantitative determinations of individual nuclides in intact or dissolved fuel specimens to be made.It should also be possible to scan irradiated fuel specimens, e.g. , plates or rods, for individual fission-product nuclides with188 BANHAM, FUDGE AND HOWES [Analyst, Vol. 91 little or no interference from other emitters present. This in turn should promote the study of, for example, the migration of fission products in irradiated fuel specimens in greater detail than has hitherto been possible. The study of the applications of germanium - lithium detectors to fission-product analysis is being continued with a second apparatus with improved geometry and efficiency, whilst the apparatus already described will continue to be in use for investigations of low- noise amplification systems. REFERENCES 1. 2. 3. 4. 5. 6. 7, 8. 9. Pell, E. M., J . AppZ. Phys., 1960, 31, 291. Freck, D. V., and Wakefield, J., Nature, 1962, 193, 669. Webb, P. P., and Williams, R. L., Nucl. Instrum. Meth., 1963, 22, 361. Tavendale, A. J., and Ewan, G. T., Ibid., 1963, 25, 185. Ewan, G. T., and Tsvendale, A. J., Can. J . Phys., 1964, 42, 2286. Howes, J. H., in preparation. Owen, R. B., and Gibbons, P. E., U.K. Atomic Energy Authority Refioyt, Harwell, AERE-M 1602, Banham, M. F., and Fudge, A. J., “The Determination of Burn Up in Nuclear Fuel Test Specimens Heath, R. L., and Cline, J. E., Report of Phillips Petroleum Company, Atomic Energy Division, Received September 132h, 1965 1965. using Zirconium-95,” to be published. Idaho Falls, Idaho, IDO-17050, 1964.

ISSN:0003-2654    

DOI:10.1039/AN9669100180

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

March, 19661 MOLD, PEYTON, MEANS AND WALKER 189 Determination of Catechol in Cigarette Smoke BY J. D. MOLD, M. P. PEYTON, R. E. MEANS AND T. B. WALKER (Research Department, Liggett and Myers Tobacco Company, Durham, North Carolina, U.S.A .) A procedure has been devised for the specific determination of catechol in cigarette-smoke condensates. This procedure should also be applicable to the determination of catechol in other materials resulting from pyrolytic or combustion processes. As the catechol is isolated without recourse to the formation of a deriva- tive, no interference is encountered as a result of the presence of guaiacol or similar compounds. Avoidance of the use of alkaline conditions throughout the procedure has permitted reproducible and high recoveries. THE presence of catechol in cigarette smoke has been known for many years without any reliable measurements having been reported concerning the amount present. This is princi- pally due to the fact that catechol is rather unstable in alkaline solution, and procedures previously used for its determination in cigarette smoke have utilised an alkaline extraction step to concentrate the acidic materials and remove contaminants.The simple monohydroxyphenolic materials can be determined reliably by gas - liquid chromatography. Application of gas - liquid chromatography to the quantitative deter- mination of catechol was reported by Janak and K0rners.l Recoveries of approximately 70 per cent. were achieved. More recently, von Rudloff2 reported the qualitative separation of catechol from other phenols by using several different gas - liquid chromatographic substrates.Difficulties were noted due to “tailing” or poor elution. Methylation has been used to furnish derivatives of phenols in cigarette smoke for subsequent separation and determinati~n,~ y4 but this is not a quantitative process for catechol, and furthermore the veratrole measured can be derived from guaiacol, which is also present in the smoke. Other workers5 have chromatographed dihydroxybenzene compounds by liquid - liquid partition on silicic acid with cyclohexane as the developing solvent. The amounts of individual phenols were determined by measurement of the optical density at 2800 A. This procedure gave good resolution and appeared well suited for the routine determination of phenolic constituents in samples of similar composition.Disadvantages were the time required and the need for making optical-density measurements on a large number of fractions. The successful use of polyamide surfaces for the qualitative separation of phenolic materials, including cate~hols,~ ?7s8 and their suggested utility for quantitative analysiss prompted us to adapt this technique for the analysis of catechol in cigarette smoke. The procedure that we have developed was designed to avoid exposure of the catechol to alkali. The smoke condensate is dissolved in aqueous acid and ether. Ether-soluble acidic and neutral components are further fractionated by extraction into aqueous borate at pH 7. Catechol and similar vicinal dihydroxy-compounds are selectively complexed by the borate and made soluble in the aqueous phase.Acidification of the aqueous extract permits recovery of these compounds by extraction with ether. Catechol is then separated from other components of this mixture by chromatography on thin layers of polyamide powder with an acidic developing solvent. Since catechol is determined in our procedure without the formation of a derivative such as the methyl ether, no interference from guaiacol is experienced. The method has given reproducible results when applied to cigarette smoke and near theoretical recovery of added known amounts of catechol. EXPERIMENTAL Catechol was unstable when stored in redistilled analytical-reagent grade ether con- taining no preservative, but no loss was observed over a 3-week period when trace amounts of sodium diethyldithiocarbamate were added to the ether.Considerable loss of catechol190 XOLD, PEYTON, MEANS AND WALKER: [Aqzalyst, Vol. 91 did occur if it was extracted from ether into an aqueous alkaline solution and was then recovered from the acidified extract by re-extraction into ether. The losses sustained in this treatment were not as great in the presence of other smoke components. The recovery of catechol was 97 per cent. when subjected to the initial ether extraction used in the present procedure. Similarly, the recovery of catechol in the borate extraction step was 98 per cent. KO significant loss was observed in 0.1 hf sodium borate at pH 7 for periods of time well in excess of that required for the borate extraction.Thin-layer chromatography on polyamide powder from another source gave quite different RF values and less desirable behaviour than did the \Yoelm polyamide powder. The initial use of the upper layer of a benzene - acetic acid - water (6 + 7 + 3) solvent for the thin-layer chromatography gave unsatisfactory results, apparently due to variations in composition of the solvent. BettslO discusses the superior stability of one-phase solvent systems over systems prepared by equilibration of two phases. The solvent mixture that was chosen (100 + 25 + 1) is a single phase and has given reproducible results. Initially, the recovery of catechol from the thin-layer chromatograms was found to vary from 78 to 96 per cent. of the theoretical value. The extent of loss was usually similar for plates prepared at the same time.Volatilisation of catechol from the polyamide film did not appear to be a source of loss, as the yield was essentially the same whether the spot was eluted immediately, or after one hour, after the drying of the plate. Also, when spots of catechol were applied diagonally across the plate and developed in the usual way, recoveries varied from 92 to 96 per cent., with no inhcation of a trend related to the extent of travel of the catechol across the plate. Consistently higher recoveries, 94 to 100 per cent., have been obtained by washing the polyamide powder with ethanol, prior to preparing the slurry. Furthermore, the ethanol- washed polyamide provides layers with less tendency to crack on drying.The recovery of catechol, added to cigarette-smoke condensate and carried through the various steps of the procedure as outlined below, was 95 to 100 per cent. The catechol spot removed from the thin-layer chromatogram of a typical cigarette- smoke extract was found to have ultraviolet absorption identical to that for an authentic sample of catechol, with little background absorption. I t had the same R, value as authentic catechol when chromatographed on borate-treated silica gel with butanol, saturated with 0.1 M sodium borate a t pH 7 , and on Whatman Xo. 1 filter-paper with chloroform (containing 1 per cent. ethanol) which had been equilibrated with methanol - water - formic acid (25 + 24 + 1) as proposed by Reio.ll The same yellow colour was obtained for both known and unknown by spraying with diazotised 9-nitroaniline. The colorimetric procedure used for the quantitative determination of catechol is a modification of the test reported by Mitchell.12 The test is given, in general, by all di- hydric phenols and it is therefore necessary to achieve an adequate separation of catechol from other compounds of this class prior to applying this test.As catechol is the pre- dominant compound of this class, present in the borate extract of cigarette smoke, the separation achieved by this method is usually adequate. Smoke from cigarettes made entirely with flue-cured tobaccos, contains some interfering substances in concentrations that could warrant extending the development of the chromatogram on longer plates. I t is possible to obtain a measure of the total dihydric phenols in the ether extract from the acidified borate solution.The intensity of the colour is comparable to that obtained with catechol for many of these compounds, such as 3-methylcatechol, 4-methylcatechol and protocatechuic acid. Pyrogallol and caffeic acid give 1.3 times the colour intensity observed for catechol. Protocatechualdehyde, coumarin-diols and naphthalene-diols give an orange colour with absorption maximum at about 450mp. These latter compounds, if present, would also contribute to the total colour intensity at 515 to 530mp. Phenol, resorcinol, guaiacol and hydroquinone do not give significant colour production at 515 to 530 mp. Results were erratic when an aliquot of the ether solution containing dihydric phenols was evaporated to dryness before mixing with the colorimetric reagent.This was remedied by adding a portion of the reagent before evaporating off the ether. APPARATUS- METHOD Smoking a$$aratus-That described by Keith and Newsome13 was used. Smoke-coZZection $asks-- JF-6910 (Scientific Glass Apparatus Co. Inc., Bloomfield, N. J.) .March, 19661 DETERMINATION OF CATECHOL I N CIGARETTE SMOKE 191 Apparatus for thin-layer chromatografhy-Desaga-Brinkmann model S-1 1 (Brinkmann Spectrophotometer-Perkin-Elmer model 350 (Perkin-Elmer Corp., Nonvalk, Conn.) . Instruments Inc., Great Neck, N.Y .). REAGENTS- a-CeZlzdose-Solka Floc (Brown Co., Berlin, New Hampshire). Ether-Mallinckrodt anhydrous analytical-reagent grade is redistilled and stabilised by the addition of 0.05 p.p.m.of sodium diethyldithiocarbamate (Distillation Products Industries). Woelm Polyamide powder-(Alupharm Chemicals, Elmont, Long Island, New York). Catechol-Re-sublimed (Aldrich Chemical Co., Milwaukee 10 Wis.) . Ferrous salt solzdion-Dissolve 0.1 g of hydrated ferrous sulphate, FeS0,.7H20, and 0.5 g of sodium potassium tartrate, NaKC,H40,.4H20 (Rochelle salt), in 100 ml of distilled water. This solution is stable for approximately 3 days. Colorimetric reagent-Mix two parts of the ferrous salt solution with five parts of 10 per cent. w/v ammonium acetate and two parts of 0.25 N ammonium hydroxide. This reagent must be freshly prepared for each set of determinations. Cigarettes-Brands A, B, C and D are non-filter-tipped cigarettes (commercially available in the U.S.A.) which contain blended flue-cured (Bright), air-cured (Burley and Maryland) and sun-cured (Turkish) cigarette tobaccos.Brands E, F, G and H are filter-tipped cigarettes (commercially available in the U.S.A.). These cigarettes also contain blends of the three types of tobaccos listed above. Cigarettes I, J and K were prepared to contain a blend of a single type of tobacco, flue-cured, sun-cured or air-cured, typical of that particular component of a commercial blend. The latter cigarettes were cased with a glycol - sugar mixture. SMOKING TECHNIQUE- Cigarettes equilibrated at 60 per cent. relative humidity and 25" C are selected to within k30 mg of the average weight desired. These are smoked mechanically in a room controlled at 25" C and 60 per cent. relative humidity.Forty-ml puffs of 2 seconds duration are taken at intervals of 60 seconds until an average butt of 30 mm remains. The smoke, produced from the sequential smoking of ten cigarettes, is condensed in a trap containing a-cellulose, which is partially immersed in a solid carbon dioxide - acetone coolant. The weight of smoke condensate is determined by the difference in weight of the cellulose trap, at 25" C, before and after smoke collection. A correction is applied for the amount of moisture introduced from the atmosphere during the puffing. To obtain the yield of catechol from the filter-tipped cigarettes without filtration, the filter materials are removed from the mouth-piece before smoking and the cigarettes are smoked to a butt length of 30mm, including the mouthpiece.EXTRACTION OF THE CATECHOL FRACTION- The smoke condensate is removed from the cellulose traps by washing with several portions of ether, 0.1 N hydrochloric acid and acetone, totalling 105, 50 and 5 ml, respectively. These extractants are then combined and equilibrated, the layers are allowed to separate, and the aqueous layer is washed five times with equal volumes of ether. The ether extracts are combined and concentrated at 30" to 34" C in a nitrogen stream to a volume of 25 ml. The ether concentrate is then extracted four times with 25-ml volumes of 0.1 M sodium borate, which has been adjusted to pH 7 with hydrochloric acid. If necessary, the pH of the first borate layer is re-adjusted to pH 7 with cold, dilute sodium hydroxide after contact with the ether concentrate.The borate extracts are cooled and acidified to pH 1 immediately upon collection. Recovery of the catechol from the acidified borate solution is accomplished by extracting four times with 100-ml volumes of ether. After the ether extract has been concentrated to 50 ml in a nitrogen stream a t 30" to 34"C, it is washed twice with 1 ml of water, concen- trated further, and dried with sodium sulphate, in the cold, overnight. The sodium sulphate is filtered from the solution, and the filtrates and rinsings are carefully concentrated in a nitrogen stream to exactly 2 ml. Losses of catechol are observed with complete evaporation of the solvent. The extraction of larger samples of cigarette smoke is accomplished, similarly, by scaling up the extracting volumes.192 MOLD, PEYTON, MEANS AND WALKER: [,4naZyst, 1701, 91 DETERMINATION OF THE TOTAL 0-DIHYDRIC PHENOLS- An aliquot of the smoke fraction containing the o-dihydric phenols, usually representing one cigarette, is mixed with 5 ml of the colorimetric reagent, the vessel is shaken thoroughly, and the ether evaporated in a nitrogen stream.The coloured solution is diluted to 10 ml with the colorimetric reagent and the visible spectrum is obtained with the colorimetric reagent in the reference cell. The absorption maximum, between 515 and 530 mp, is calculated from catechol standardisation data, and the amount of o-dihydric phenols is calculated as if they were catechol. THIN-LAYER CHROMATOGRAPHIC SEPARATIOK OF CATECHOL- Chromatographic plates (20 x 20 cm) are coated with 0.35 mm of Woelm polyamide powder.amide powder in 45 ml of methanol - water (3 + 1). A narrow area along each edge is scraped free of polyamide to promote uniformity of the solvent flow. An aliquot (200 pl) of the catechol extract, equivalent to the smoke condensate from one cigarette, is applied to the lower left corner of each of two plates. A sample of 110 pg of pure catechol is similarly applied to the middle of the lower side of the two plates. After the application solvent has evaporated, development is carried out by ascending chromatography in benzene - acetic acid - water (100 -+ 25 -t- 1). The solvent front usually reaches the top of the plate within an hour. The plates are then removed from the chromatography chamber and the solvents are allowed to evaporate until the plates appear barely dry: extended drying will cause the powder layer to crack.Chromatography is continued by using distilled water to develop the plates in a direction perpendicular to that of the first chromatography. This usually requires about 45 minutes. The plates are partially dried in air, sprayed lightly with the ferrous salt colorimetric reagent, and again partially dried in air. Exposing the damp plate briefly to ammonia vapour will aid in the development of the characteristic purple colour. Both the smoke - catechol spot and the control - catechol spot are marked before the plate has dried completely. After drying thoroughly in air, each spot is removed by suction on to a sintered-glass filter14 and washed into a 10-ml vessel with the ferrous salt colorimetric reagent.COLORIMETRIC DETERMINATION OF CATECHOL- The visible spectrum is measured within 2 hours with the colorimetric reagent in the reference cell. The absorbance is measured a t the maximum, which occurs between 515 and 530 mp. The concentration of catechol in the sample is read off from the curve obtained, by measuring this absorbance for several concentrations of standard catechol. The standardi- sation curve is re-determined for each colorimetric reagent preparation and, at concentrations between 50 and 300 pg per 10 ml, obeys Beer’s law. The value obtained for the smoke - catechol content is corrected for the recovery achieved for control samples of catechol treated in the same manner.Five plates are prepared a t one time by spreading a slurry of 5 g of the poly- RESULTS AND DISCUSSION Catechol analyses for smoke from several nun-filter-tipped cigarettes are given in Table I. The results are expressed both in terms of pg of catechol per cigarette, and as the catechol percentage of condensate. The latter values tend to compensate for variations in the weights of smoke produced due to differences in length or burning characteristics of the cigarettes. The standard deviation calculated for the results presented in Table I is +0.024 per cent. The level of catechol in smoke from cigarettes made with a blend of air-cured (Burley) tobaccos was considerably lower than for smoke from cigarettes made with either flue-cured or sun-cured tobaccos. To evaluate the effect of filtration on the concentration of catechol in cigarette smoke, it is necessary to correct for the moisture content of the smoke.This is required as the filters remove a disproportionate amount of water. When this correction was applied to the analyses performed on smoke from several different brands and types of filter-tipped cigarettes (E, I;, G and H, Table 11), the results indicated no appreciable effect of the filter on the concentration of catechol in the smoke, i.e., the catechol is removed by these filters to an extent equivalent to the removal of the total dry smoke. This would suggest that negligible The reasons for this difference are being investigated.March, 19661 193 DETERMINATION OF CATECHOL IN CIGARETTE SMOKE TABLE I CATECHOL IN SMOKE FROM KON-FILTER-TIPPED CIGARETTES Smoke Catechol content- condensate, r A > Ing per t% Per Type of cigarette cigarette cigarette Cigarette A, 85-mm blended flue-cured, air-cured 48 145 and sun-cured tobaccos 161 49 127 130 Cigarette B, 85-mm blended flue-cured, air-cured 37 113 and sun-cured tobaccos 131 36 118 130 Average .. Average . . Cigarette C, 70-mm blended flue-cured, air-cured 33 92 and sun-cured tobaccos 93 35 102 102 Cigarette D, 70-mm blended flue-cured, air-cured 35 76 and sun-cured tobaccos 95 35 97 96 94 100 53 260 180 54 228 244 65 193 198 52 168 186 39 50 50 39 46 43 Average . . Average . . Average . . Average . . Average . . * Omitted from calculation of average and standard deviation. Cigarette I, 85-mm blend of flue-cured tobacco Cigarette J, 83-mm blend of sun-cured tobacco Cigarette K, 85-mm blend of air-cured tobacco percentage of condensate 0.30 0-33 0.26 0.27 .. 0.29 0.3 1 0.36 0.33 0.36 . . 0.34 0.28 0.28 0.29 0.29 . . 0.28 0.22 0.27 0.28 0.28 0.27 0.29 . . 0.27 0.49 0.34* 0.42 0-45 . . 0.45 0.35 0.36 0.33 0.36 . . 0.35 0.13 0.13 0.12 0.11 . . 0.12 amounts of catechol are present in the vapour phase of the smoke, otherwise its selective removal by the cellulose acetate filters, as is noted for the more volatile monohydric phenols, would be anticipated. TABLE I1 CATECHOL IN SMOKE FROM 85-mm FILTER-TIPPED CIGARETTES Filter intact Filter removed f Dry r smoke, * mg per Brand mm Filter-tipped type cigarette E 17 acetate 26 F 20 acetate 20 G 20 acetate + charcoal 29 H 20 acetate -+ charcoal 21 Catechol 1 percentage of dry PLg smoke 103 0.39 97 0.49 118 0.4 1 92 0.44 r Dry 7 smoke, * ing per cigarette 42 31 44 26 1 Catechol -7 percentage of dry tLg smoke 146 0.35 155 0.50 176 0-40 116 0.45 * The smoke weights are corrected to a dry basis by using moisture values from duplicate smoke collections determined by Karl Fischer titrations.194 MOLD, PEYTON, MEANS AND WALKER [Analyst, Vol.91 The colorimetric test for o-dihydric phenols, applied to the borate-extractable fraction of cigarette smoke, prior to chromatography on polyamide, and calculated as catechol, indicated a total content for these materials about twice the value of that measured for catechol (see Table 111). Smoke samples used for these analyses were prepared under the supervision of D. H. Woods. TABLE I11 TOTAL O-DIHYDRIC PHENOLS IN SMOKE FROM NON-FILTER-TIPPED CIGARETTES Studies are in progress to identify these materials. Smoke o-Dihydric phenols (as catechol) fng Per r-lg Per percentage of condensate, r h \ cigarette cigarette condensate Cigarette A, 85-mm blended flue-cured, air-cured and sun-cured tobaccos . . . . . . 49 336 0.69 Cigarette J, 85-mm blend of sun-cured tobacco 53 286 0.54 Cigarette K, 85-mm blend of air-cured tobacco 39 107 0.27 Cigarette I, 85-mm blend of flue-cured tobacco 54 526 0.98 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. REFERENCES JanAk, J., and Komers, R., Colln Czech. Chem. Cornmun., Engl. Edn, 1959, 24, 1960. von Rudloff, E., J . Gas Chromat., 1964, 2, 89. Commins, B. T., and Lindsey, A. J., Analytica Chim. Acta, 1956, 15, 557. Carruthers, W., and Johnstone, R. A. W., Nature, 1960, 185, 762. Young, J. H., Analyst, 1961, 86, 520. Endres, H., and Hormann, H., Angew. Chern., Int. Edn, 1963, 2, 254. Martin, W. N., and Husband, R. M., Analyt. Chem., 1961, 33, 840. Halmekoski, J., and Hannikainen, H., Suornen. Kern., 1963, B36, 24. Gasparic, J., Petranek, J., and Borecky, J., J . Chromat., 1961, 5, 408. Betts, T. J., J . Pharm. Sci., 1964, 53, 794. Reio, L., J . Chrornat., 1968, 1, 338. Mitchell, C. A., Analyst, 1923, 48, 2. Keith, C. H., and Newsome, J. R., Tob. Sci., 1957, 1, 51. Matthews, J. S., Pereda, V., A. L., and Aguilera, P., A., J. Chrornat., 1962, 9, 331. Received A$ril 12th, 1965

ISSN:0003-2654    

DOI:10.1039/AN9669100189

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

March, 19661 CURTHOYS AND SIMPSON 195 Determination of Zinc in Trace-element Superphosphate by A.C. Polarography BY G. CURTHOYS AND J. R. SIMPSON (Newcastle University College, The University of New South Wales, Australia) Zinc has been effectively determined in “trace-element superphosphate” with an a.c. polarographic technique. This technique is both rapid and accurate and compares favourably with the atomic-absorption method. The zinc is maintained in solution by polarographing in an acid electrolyte of M hydrochloric acid a t a pH of less than 1. The method eliminates the time- consuming process of separation from interfering ions. The presence of the hydrogen reduction wave does not materially interfere with the zinc reduction wave as happens in conventional d.c. polarography .THE application of conventional d.c. polarography has been used by Heller et al.,l Walkley2 and Piper3 to determine zinc in soil and plant material. They extracted the zinc with dithizone and evaporated the extract to dryness. The residue was dissolved in a basal solution of ammonium chloride and potassium thiocyanate. The zinc was determined polarographically ; it has also been determined polarographically in biphthalate? ammoniaca15 and fluoride6 electrolytes. The above investigations were carried out in alkaline, or near-alkaline, solutions because of the interference of the hydrogen wave occurring close to the zinc wave. Breyer, Gutman and Hacobian’,* have shown that a.c. polarographic waves 40 mV apart are clearly separable and have, in fact, obtained well defined curves for zinc in 0.1 N hydrochloric acid and 0-5 N hydrochloric acid.METHOD REAGENTS- All the reagents used were analytical-reagent grade chemicals. Nitric acid, concentrated. Hydrochloric acid, 10 N. Suulphuric acid. Zinc sulphate solution-Prepare a standard solution by dissolving 0.2200 g of zinc sulphate heptahydrate in distilled water. Add to the solution 50 ml of 10 N hydrochloric acid and dilute the solution to exactly 500 ml with distilled water (1 ml of the solution = 0.0001 g of zinc). SAMPLES- A.O.A.C. ~pecifications.~ at 90” to 100” C for 4 hours and place them in a sealed bottle. Sample the normal superphosphate and “trace-element superphosphate” according to Crush the samples to pass through a 40-mesh sieve, dry them APPARATUS- Polarograph-A manual a.c.polarograph was used, similar to that described by Breyer, Gutman and HacobianlO with a few minor modifications. The cell consisted of a 100-ml squat beaker into which the test solutions were placed. The dropping-mercury cathode was lowered into the cell to within 15 to 20 mm of the mercury- pool anode. The head of mercury of 100cm gave a drop time of 1 drop per 4.0 second, with a mass (m) = 1.44mg per second. Standard polarograms were carried out at the same time as the experimental work and the temperature was maintained constant to within k0.5” C. The peak currents were measured from the interpolated base-line.196 CCRTHOYS AND SIMPSON: DETERhIINATIOS OF ZINC Ih’ [A?UdySt, vO1. 91 Zinc in the trace-element superphosphate samples was determined with an atomic- absorption spectrophotometer similar to that described by Box and Walshll and containing a hollow zinc cathode emitting a resonance line at 213-8 mp.PROCEDURE- Prepare five standard solutions by weighing 2.000 g of the normal superphosphate into a 250-ml beaker. Add to the solid 5ml of concentrated nitric acid, 5ml of concentrated hydrochloric acid and evaporate the solution to dryness. Dissolve the residue in 10 ml of 10 s hydrochloric acid and 70 ml of hot distilled water. Boil the solution, then filter it through a Whatman No. 41 filter-paper, and wash the residue with 6 small washings of hot distilled water . Cool the filtrate, dilute it to exactly 100 ml in a calibrated flask and mix it well. Transfer by pipette a 20-ml aliquot into a 500-ml calibrated flask with 48 ml of 10 N hydrochloric acid, dilute the solution to exactly 500 ml with distilled water and mix it well.Transfer by pipette a 50-ml aliquot of this solution into each of five 100-ml squat beakers. Introduce 1, 2, 3, 5 and 6ml of the standard zinc solution to the respective beakers and mix the contents well. Polarograph the solutions between -0.90 and -1.34 volt with a mercury-pool anode and an a.c. potential of 2.87 mV r.m.s. Transfer a 50-ml aliquot of the above solution to a 100-ml squat beaker and polarograph it as a blank determination on the normal superphosphate and the reagents used. Place duplicate 2-g samples of the “zinc-trace superphosphate” into 250-ml beakers and evaporate them to dryness with 5 ml of concentrated nitric acid and 5 ml of concentrated hydrochloric acid.Dissolve the residues in 10 ml of concentrated hydrochloric acid and 70 ml of hot distilled water. Boil the solutions and filter them through \$’hatman No. 41 filter-paper, washing with 6 small washings of hot distilled water. Cool the filtrates, dilute to exactly 100ml in a calibrated flask and mix them well. Transfer by pipette a 20-ml aliquot into a 500-ml calibrated flask together with 48ml of 10 N hydrochloric acid and dilute the solution to exactly 500 ml with distilled water. Transfer a portion of each to separate 100-ml squat beakers and polarograph between -0.90 and - 1.34 volt with a mercury-pool anode under the, same cell conditions as used for the standard. Draw a calibration curve from the standard polarogram for the zinc, and determine the zinc in the trace-element superphosphate.RESULTS Although the influence of the hydrogen ion reduction on the base-line is evident, it does not interfere with the zinc wave or the determination of its peak height. Zinc gave fairly well defined peaks in hi hydrochloric acid with a half-wave potential at -1.02 volt with a mercury-pool anode. No interference resulted from the presence of phosphate or iron. The polarograms for some of the additions of standard zinc solution to the normal superphosphate are given in Fig. 1 (a), ( b ) and (c), and show a corresponding increase in peak height with concentration. The blank determination, represented by Fig. 1 ( d ) , consisted of the reagents and the normal superphosphate and gave no wave for zinc.From the peak heights at different concentrations of zinc, as shown in Table I, the cali- bration graph was drawn. The calibration graph gave a straight line passing through the origin over the range 0 to 10.7 x 10-3g of zinc per litre. TABLE I P E A K HEIGHTS AT DIFFEREXT ZINC CONCESTRATIONS Concentration of zinc, Current, g per litre PA 1.96 x 10-3 3 3.85 x 10-3 5.5 5.66 x 8 9-09 x 10-3 13 10.7 x 10-3 15-5 The polarograms of duplicate samples for zinc in trace-element superphosphate carried out under the same cell conditions as the standards gave similar, well defined peaks. WithMarch, 19661 TRACE-ELEMENT SUPERPHOSPHATE BY A.C. POLAROGRAPHY I I -1.0 -1.2 1 I -1-0 -1.2 L 197 -1.0 -1.2 -1.0 - I .2 Potentia1,Volts Fig. 1 . Polarogram of zinc standards in “normal” superphosphate at 21.1” C.Base electrolyte M hydrochloric acid, a.c. potential 2.87 mV r.m.s. (a) 1-96 x g of zinc per litre; ( b ) 56.6 x g of zinc per litre; ( 6 ) 10.7 x g of zinc per litre; ( d ) “normal” superphosphate (blank) high zinc content, increased dilution was necessary. The peak heights were measured and the percentage of zinc was determined from the calibration curve. The concentration of zinc in the samples was also determined with an atomic-absorption spectrophotometer, the comparison of the results being shown in Table 11. TABLE I1 COMPARISON OF RESULTS Acid digestion, Atomic absorption, Sample per cent. of zinc per cent. of zinc Zinc - superphosphate . . 1.25 1.26 1-21 1-26 1.23 1.24 1.31 1.31 1.33 1.28 1.28 1-30 Mean = 1.24 Mean = 1.30 Standard deviation 0.015 Standard deviation 0.017 Zinc may be determined by a.c. polarography in superphosphate containing other trace elements, such as copper, by using a procedure identical with that described above.198 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. [Analyst, VOl. 91 CURTHOYS AND SIMPSON REFERENCES Heller, K., Kuhla, G., and Machek, F., Mikrochemie, 1937, 23, 78. Walkley, A., Aust. J . Ex$. Biol. Med. Sci., 1942, 20, 139. Piper, C. S., “Soil and Plant Analysis, Waite Agricultural Research Institute, South Australia, Jones, G. B., Analytica Ckim. Acta, 1954, 11, 88. Menzel, R. G., Jackson, M. L., Analyt. Chem., 1951, 23, 1861. Eve, D. J., Verdier, E. G., Ibid., 1956, 28, 537. Breyer, B., Gutman, F., and Hacobian, S., Aust. J . Scient. Res., 1950, 3, 559, --- , Ibid., 1950, 3, 567. “Offikial Methods of Analysis,” Ninth Edition, Association of Official Agricultural Chemists, Breyer, B., Gutman, F., and Hacobian, S., Aust. J . Chem., 1953, 6, 188. Box, G. F., Walsh, A., Spectrochim. A d a , 1960, 16, 255. 1950, p. 350. 1960, p. 6. Received November 20th. 1964

ISSN:0003-2654    

DOI:10.1039/AN9669100195

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

March, 19663 BELKAS AND SOULIOTIS 199 Simultaneous Determination of Iodine and Bromine in Urine by Neutron-activation Analysis BY E. P. BELKAS AND A. G. SOULIOTIS (Chemistry Department, hTuclear Research Centre “Democritus,” Athens, Greece) Neutron-activation analysis was used for the simultaneous determination of iodine and hromine in urine. The activated iodine and bromine were separated by radiochemical methods. The 0.46 Me\’ and 0.55 MeV peak areas of lZR1 and 8zBr, respectively, were measured by nieans of a multi- channel analyser. The amounts of iodine and bromine were found to be of the order of lo-’ and of urine, respectively, for normal human beings of different ages. g ml IODINE is found in urine both in inorganic (80 per cent.) and organic (20 per cent.) chemical f0rms.l Lsually, iodine is found in the various biological tissues as an organically bound species, but it cannot be determined until after mineralisation. The order of magnitude of the mineral iodine so obtained, purified by distillation, extraction, ion exchange and so on, is determined by a classical titrimetric or colorimetric method, or from its catalytic action upon the rate of reduction of ceric sulphate by arsenous oxide.2 The rate of this reaction, slow in the absence of a catalyst, is increased by the presence of micro amounts of iodine.Although the sensitivity of this catalytic reaction is of the order of 04002 pg for iodine determinati~n,~ the results of this method are not good due to the disadvantage of the im- purity of the analytical reagents, and to the presence of iodine in the laboratory.Thus neutron-activation analysis, which presents high sensitivity and good precision in comparison with other analytical methods, has been used by several investigators for the quantitative determination of iodine and bromine in a variety of biological materials. Iodine was deter- mined as thyroglobulin i ~ d i n e , ~ blood-serum and serum organically-bound i ~ d i n e , ~ ,6 blood iodine,’ stable iodine up-taken by the thyroid8 and as a constituent of different biological material^.^,^^ ,11 9 l 2 Bromine was determined in a series of biological material^.^^^^^^^^^^^ 9 1 7 9 1 8 Although there are many papers on radioactive iodine determination in urine,lg y 2 0 ,21 ,22 923 ,24 rnilkg925 and plasma,26 not much work has been done on the determination of stable iodine in urine, especially by radioactivation analysis.As a contribution to these studies, iodine and bromine were simultaneously determined in urine by radioactivation-analysis techniques. On irradiating any material with neutrons, various nuclear reactions take place, those in Table I being of interest for iodine and bromine d e t e r r n i n a t i ~ n . ~ ~ * ~ ~ TABLE I NUCLEAR REACTIOKS Main radiation A4ctivation encrgics, MeV Abund- cross- 7- ancc, section, Half- fl cnergy, y energy r--+ r-\ lZ7I 1271 (n,y) 1281 100 5.60 24-99 min. 1.67 16 0.46 17 2.12 76 0.55 75 0.78 83 81Br 81Br (n,y) 82Br 49.48 1-60 36.87 hr 0.44 100 1.04 29 1.32 28 Nuclide Reaction % barns life I ~ X . 76 Possible interference from lasXe (n,p) lZ8I with a Xe matrix sZKr (n,p) E2Br with a Kr matrix EXPERIMENTAL IRRADIATION- Transfer an aliquot of about 6 ml of biological liquid, by pipette, into a polythene snap-closure tube of diameter 26 mm and height 50mm, having along its axis another polythene200 BELKAS AND SOULIOTIS : SIMULTANEOUS DETERMINATION OF IODINE [Analyst, Vol.91 snap-closure tube of diameter 15 mm and height 50 mm, that can be stoppered and fused. Add 6 ml of the standard iodine and bromine solution, mentioned below, into the central tube and then stopper and fuse it. A = External polythene tube containing B = Central polythene tube containing iodide and potassium bromide urine standard solution of potassium Fig. 1. Target for irradiation Irradiate the target for 15 minutes at a flux of 10l2n.cm-2 second-l. We sent our prepared target, by means of the pneumatic system, to the core of the swimming pool of the “Democritus” nuclear reactor. REAGENTS- Use analytical-grade reagents. Potassium iodide standard solution-Make an aqueous solution containing 10 mg ml-l of Potassium bromide standard solution-Make an aqueous solution containing 10 mg ml-l Potassium iodide and potassium bromide standard solution-Prepare an aqueous solution mg ml-l of bromine of mixture, taken from the standardised iodine. of bromine. of lod4 mg ml-l of iodine and solution of the carrier. Use triply distilled water. Perhydrol. Sodium nitrite solution, 2.5 N and N sodium nitrite. Sulphuric acid, concentrated. Sodium hydroxide solution, 7-5 per cent. sodium hydroxide.Carbon tetrachloride. Nitric acid, concentrated, 6 N and 0-01 N. Sodium hydrogen sulphite solution, N. Silver nitrate solution, 0.1 N. Ethanol. Potassium permanganate, powder. Potassium permanganate solution, 2 per cent. potassium permanganate. Hydroxylammonium chloride solution, M. APPARATUS- and a Plexi-glass filter-funnel were used. Modified apparatus was used to increase chemical yield. A Pyrex distillation apparatus ISOLATION OF IODINE AND BROMINE BY DISTILLATON- After irradiation transfer by pipette into the distillation apparatus, 5 m l of urine con- taining 1 ml of iodine plus 2 ml of bromine carrier solutions, respectively. Add the following reagents : 2 ml of concentrated sulphuric acid, 2 ml of perhydrol and 1 ml of N sodium nitrite solution. Begin distillation by heating and introducing air.Introduce the distillate and air into 10 ml of 7.5 per cent. sodium hydroxide solution contained in a separating funnel im- mersed in an ice - water mixture. After a few minutes add the same volumes of perhydrol and sodium nitrite and continue the distillation until white sulphur trioxide vapour is produced. The duration of the distillation procedure was 10 minutes.March, 19661 AND BROMINE I N URINE BY NEUTRON-ACTIVATION ANALYSIS 201 A A = Compressed air from cylinder D = Asbestos shield B = IO-ml funnel containing sodium E = Air-cooled tube nitrite, sulphuric acid and a 30% solution of hydrogen peroxide F = 250-ml flask containing sodium C = 50-ml round-bottom flask contain- ing urine, potassium iodide and G = Beaker containing ice-water mix- potassium bromide ture Fig.2. Pyrex distillation apparatus hydroxide A = Screw-cylinder B = Filter disc C = Screw-funnel Fig. 3. Plexi-glass filter funnel ISOLATION OF IODINE BY REDOX AND PRECIPITATION- Pour 10 ml of carbon tetrachloride into the solution contained in the separating funnel. Gently neutralise and slightly acidify this alkaline solution with 6 N nitric acid. Add 1 ml of 2.5 per cent. sodium nitrite drop by drop until the organic phase turns pink and separates. Repeat the same oxidation extraction step to the aqueous phase. Keep the aqueous layer containing bromine so that it can later be subjected to the bromine isolation procedure.202 BELKAS AND SOULIOTIS : SIMCLTAKEOUS DETERMINA4TTON OF IODINE [A?ZdySt, VOl.91 Gather the organic phases containing the iodine and subject them to a reduction step by adding 10 ml of distilled water and a few drops of N sodium hydrogen sulphite. Separate the aqueous and organic phases and repeat the same reduction step with the organic phase, which can then be discarded. Collect the portions of aqueous phase and add 1 ml of 6 IC’ nitric acid. Heat the solution so as to expel the sulphur dioxide and the few globules of carbon tetra- chloride present. Add a 2-ml portion of 0.1 N silver nitrate. Filter the silver iodide precipitate, rinse the precipitate with 0.01 N nitric acid solution, distilled water and finally with ethanol. Mount the filter-paper with the precipitate on an aluminium disc for counting. The chemical yield averaged 90 per cent., and the time required was 10 minutes for the redox steps and 5 minutes for the precipitation - filtration procedure.ISOLATION OF BROMINE BY REDOX AND PRECIPITATION- Add a 10-ml portion of carbon tetrachloride, 2 ml of concentrated nitric acid and powdered potassium permanganate, until the pink colour of permanganate is visible. When the organic phase becomes brown, separate it immediately. I t was found that, for an instance when separation of the two phases was not achieved due to the excess of permanganate added, one or more mechanical decantations of the mixture from one separating funnel into another gave satisfactory separation of the two phases. Subject the aqueous phase to two more identical oxidation and extraction processes by using 1 ml of concentrated nitric acid and 2 ml of 2 per cent.permanganate solution. Collect the organic phases and reduce them by using 10 ml of distilled water and 1 ml of M hydroxyl- ammonium chloride. Separate the aqueous and organic layers and repeat the same reduction step, using 0.5 ml of reducing agent, on the organic phase, which can then be discarded. Gather the aqueous phases and subject them to the redox procedures mentioned above by using N sodium hydrogen sulphite. Add a 1-ml portion of 6 x nitric acid to the collected aqueous solutions, and then heat so as to expel sulphur dioxide and carbon tetrachloride. Add a 4-ml portion of 0.1 N silver nitrate. Treat the silver bromide precipitate in the same way as the iodide and mount for counting. We found that the chemical yield averaged 70 per cent., and the time required was 15 minutes for the redox steps and 5 minutes for the precipitation - filtration procedure.Subject the aqueous solution containing bromine to the following treatment. The standards were treated in an identical manner to the urine sample. DETERMINATION O F RADIOACTIVITY- Count the silver iodide precipitate immediately for 10 minutes on a 3 x 3-inch sodium iodide (Tl) crystal counter, connected with an Intertechnique 400-channel transistorised analyser, adjusted to count energies from 0 to 2 MeV. Mount a 8-mm thick Plexi-glass block on the crystal to cut off Bremsstrahlung. Print the 0.46-MeV photopeak area of the iodine-128 and compare it with that of the standard. Count the silver bromide precipitate next day for 10 minutes under the conditions mentioned above.Print the 0.55-ICIeV photopeak area of the bromine-82 and compare it with that of the standard. GAMMA SPECTROMETRIC EXAMINATION OF THE ISOLATED RADIO-ISOTOPES- Gamma-ray spectrometry confirmed the absence of any y-emitting radionuclides as contaminants in the isolated precipitates of iodine-128 and bromine-82 coming from the aiialysed urine sample. DETERMINATION OF THE HALF-LIFE OF THE ISOLATED RADIO-ELEMENTS- This was accomplished by plotting the decay curves for silver iodide and silver bromide precipitates. The half-lives were obtained from the slope of the straight line calculated by the method of the least squares. A value of 25 minutes with a standard error of +0.013 minutes was found for iodine, and a value of 36-88 hours with a standard error of +0-21 hours for bromine, compared with 24-99 minutes and 36.87 hours, respectively, reported in the literature .27 928 RESULTS Iodine and bromine quantitative results in urine were obtained for normal human One special case is reported of a person individuals (male and female) of different ages.March, 19661 AND BROMINE IN URINE BY NEUTRON-ACTIVATION ANALYSIS 203 whose first urine sample indicated high iodine content in comparison with the content of other samples, and with those from the same person after a few days from the first sampling.This was due to the fact that the person concerned had sustained food poisoning and was being treated with Mexaform Ciba medicine containing iodochlorhydroxyquinoline. The values found were of the order of 10-7 mg ml-l and mg ml-l for iodine and bromine, respec- tively. The results are shown in Table 11.TABLE I1 CONCENTRATION OF IODINE AND BROMINE IN HUMAN URINE Name G. -4. S. A.C.C. A.G.V. G.A.S. P.C.C. A.G.S. A. J.S. S.G.S. S.G.S. C.A.K. ,4ge, in years 1 2 24 38 29 30 45 58 58 so Sex male female female female female male male female female female Iodine, in p.p.m. 0-160 0.085 0.195 0.225 0.305 0.170 0.165 1.980 0.150 0.175 Bromine, in p.p.m. Remarks 5.3s - 5.82 - 2.78 - 4.3 1 - 9.47 - 8.29 - 9-63 in medical cure 2.4 1 - 4.28 - 11.9 in pregnancy DISCUSSION By the technique mentioned above iodine and bromine were simultaneously determined by one irradiation. From the values found it is confirmed that urine is enriched in iodine and bromine by a factor of about 2 with respect to The errors in iodine determination by titrimetric, colorimetric and catalytic classical chemical methods, mainly due to the impurity of the analytical reagents, are eliminated.The isolated precipitates of silver iodide and silver bromide showed remarkable radiochemical purity. The results were reproducible within a relative error of less than t 3 per cent., and the sensitivity reached values of p.p.m. for iodine and bromine, respectively, for a neutron flux of 1012 n. cm-2 second-l and an irradiation time of 15 minutes. This technique could be easily applied for precise investigation of different thyroid diseases due to its high sensitivity and good precision. It could also be applied to the simultaneous determination of these two halogens in almost every biological material.The authors wish to express their thanks to A. P. Grimanis for helpful discussions. They also appreciate the valuable technical assistance of the N.R.C. “Democritus” nuclear-radio- chemical analysis group personnel. p.p.m. and 1. 3. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. REFERENCES Fletcher, K., Biochem. J., 1957, 17, 136. Sandell, E. B., and Iiolthoff, I. RI., il.likvochi?n. Acta, 1937, 1, 9. Lachiver, F., Thesis: Facultk des Sciences de Paris 1954, Masson, Paris, 1966. Brues, ;I, &I., and Robcrtson, 0. H., Kept. ANL, AECD-20094 (1947). Leonhardt, !A’., Ir‘evmnevgie, 1961, 4, 305. Manney, T. K., and Larochc, G., Kept. Calif. ITniv. Uerkclcy, Lawrence Kad. Lab. UCKL-9897, Kellershohn, C., Comar, D., and Le-Poec, C., Int.J . A p p l . Ratliat. Isotopes, 1961, 12, 87. LVagner, H. N., Selp, Vr. E., and nowling, J . H., .I. Cliiz. 1117iesf., 1961, 40, 1984. Bergh, H., Second United Nations International Conference on Peaceful Uses of Atomic Energy, Coinar, D., Rept. CEA-2095, p. 61 (1962). Comar, I),, and I<ellershohn, C’., Comptes Reiidzies des Joiwne‘es d‘Etudes stir l’’4 nalyse par ‘4 ctiuation, Comar, D., Le-Poec, C., Joly, M., and Kellershohn, G., Bull. SOC. Chiun. Fr., 1961, 56. Beyermann, K., 2. analyt. Chem., 1961, 183, 199. Bowen, H. J. M., Biochem. J., 1959, 73, 381. Bomen, H. J . M., and Cawse, P. A., U.K. Atomic Energy Authority Report AERE-R 2925, Harwell, Hall, T. A., Nucleonics, 1954, 12, 34. Samsahl, H., and Siiremark, R., Rept. .4E-61, p. 22 (1961). __ ~ , in “Proceedings of the 1961 International Conference on Modern Trends in Activation Analysis, December 15-16, 1961,” College Station, Texas, Agricultural and Mechanical College, 1961, pp. 27 30. Volume 18, paper 586, p. 508. Grenoblc, 1961., 71. 1959, p. 40. 1962, pp. 149-154.204 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. BELKAS AND SOULIOTIS [Analyst, VOl. 91 Arnott, D C., and Wells-Cole, J., Nature, 1953, 171, 269. Craig, A., and Jackson, M., Ibid., 1951, 167, 80. Jaworowski, 2.. Nucleonika, 1960, 5, 81. Marriott, J. E., Analyst, 1959, 84, 33. Purves, H. D., Nature, 1952, 169, 111. Schrodt, A. G., Rept. WASH-736, 112-30 (1957). Farabee, L. E., Rept. ORNL-3347, p. 149-52 (1962). Ekins, R. P., Physics Med. Biol., 1959, 4, 182. Allen, R. A., Smith, D. B., and Hiscott, J. E., U.K. Atomic Energy Authority Report, AERE-R Koch, R. C., “Activation Analysis Handbook,” Academic Press, New York, 1960, pp, 92 and 128. Bowen, H. J. M., Biochcm. J.. 1959, 73, 381. 2938, Harwell, Second Edition, 1961, pp. 42 and 89. Received Murch 12th, 1965

ISSN:0003-2654    

DOI:10.1039/AN9669100199

出版商:RSC    

年代:1966

数据来源: RSC