摘要:

THE ANALYSTTHE ANALYTICAL JOURNAL OF THE CHEMICAL SOCIETYEDITORIAL ADVISORY BOARD"Chairman: H. J. Cluley (Wembley)"L. S. Bark (Salford)R. Belcher (Birmingham)L. J. Bellamy, C.B.E. (Waltham Abbey)L. S. Birks (U.S.A.)E. Bishop (Exeter)L. R. P. Butler (South Africa)"R. M. Dagnall (Huntingdon)E. A. M. F. Dahmen (The Netherlands)A. C. Docherty (Billingham)D. Dyrssen (Sweden)J. Hoste (Belgium)H. M. N. H. Irving (Leeds)H. Kaiser (Germany)M. T. Kelley (U.S.A.)W. Kemula (Poland)"W. T. Elwell (Birmingham)"J. A. Hunter (Edinburgh)"G. F. Kirkbright (London)G. W. C. Milner (Harwell)G . H. Morrison (U.S.A.)"J. M. Ottaway (Glasgow)"G. E. Penketh (Billingham)E. Pungor (Hungary)D. I. Rees (London)"R. Sawyer (London)P. H. Scholes (Sheffield)*W.H. C. Shaw (Greenford)S. Siggia (U.S.A.)A. A. Smales, O.B.E. (Harwell)A. Walsh (Australia)T. S. West (Aberdeen)A. L. Wilson (Medmenham)P. Zuman (U.S.A.)*A. Townshend (Birmingham)" Members of the Board serving on The Analyst Publications CommitteeREGIONAL ADVISORY E DlTO RSDr. J. Aggett, Department of Chemistry, University of Auckland, Private Bag, Auckland, NEWProfessor G. Ghersini, Laboratori CISE, Casella Postale 3986, 201 00 Milano, ITALY.Professor L. Gierst, Universit6 Libre de Bruxelles, Facult6 des Sciences, Avenue F.- D. Roosevelt 50,Professor R. Herrmann, Abteilung fur Med. Physik., 63 Giessen, Schlangenza hl 29, GERMANY.Professor Axel Johansson, lnstitutionen for analytisk kemi, Tekniska Hogskolan, Stockholm, 70,Professor W.E. A. McBryde, Dean of Faculty of Science, University of Waterloo, Waterloo, Ontario,Dr. W. Wayne Meinke, KMS Fusion Inc., 3941 Research Park Drive, P.O. Box 1567, Ann Arbor,Dr. I.Rubegka , Geological Survey of Czechoslovakia, Kostelni 26, Praha 7, CZECHOSLOVAKIA.Professor K. Saito, Department of Chemistry, Tohoku University, Sendai, JAPAN.Dr. A. Strasheim, National Physical Research Laboratory, P.O. Box 395, Pretoria, SOUTH AFRICA.ZEALAN D.B ruxelles, BELGIUM.SWEDEN.CANADA,Mich. 48106, U.S.A.Published by The Chemical SocietyEditorial: The Director of Publications, The Chemical Society, Burlington House,London, W1 V OBN. Telephone 01 -734 9864. Telex No. 268001.Advdrtisements: J. Arthur Cook, 9 Lloyd Square, London, WC1X 9BA. Telephone 01 -837 631 5.Subscriptions (non-members): The Chemical Society Publications Sales Office, Blackhorse Road,Letchworth, Herts., SG6 1 HN.Volume 101 No 1200 March 19760 The Chemical Society 197

ISSN:0003-2654    

DOI:10.1039/AN97601FX009

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

ANALAO 101 (1 200) 145-224 (1 976)ISSN 0003-2654March 1976THE ANALYSTTHE ANALYTICAL JOURNAL OF THE CHEMICAL SOCIETYCONTENTS145146148Editorial : The Centenary of The Analyst-F. A. RobinsonThe Analyst: 100 Years of Development-G. W. C. MilnerExtracts from Issue No. 1, March, 1876.REVIEW PAPERRecent Advances in the Ring Oven Technique-Herbert Weisz 152ORIGINAL PAPERSFungicide Residues. Part V. Determination of Residues o f Chloraniformethan inGrain and Cucumbers by Gas Chromatography-R. A. Hoodless and M. SargentThe Determination of Chlorhydroxyquinoline i n Medicated Pig Feeds. Part II.Ultraviolet Spectrophotometric Batching Assay and Gas-chromatographicAssay for Mono- and Dichloro Components-T. Cowen and W. F. HeyesA Simple Method for Monitoring Excessive Levels of Lead i n Whole Blood UsingAtomic-absorption Spectrophotometry and a Rapid, Direct NebulisationTechnique-K.C. Thompson and R. G. GoddenSolvent Mediator Studies on Barium lon-selective Electrodes Based on a Sensorof theTetraphenylborate Salt of the Barium Complex of a Nonylphenoxypoly-(ethy1eneoxy)ethanol-A. M. Y. Jaber, G. J. Moody and J. D. R. ThomasA Semi-automated Method for the Determination of Inorganic, Organic andTotal Phosphate in Sediments-K. I. Aspila, Haig Agemian and A. S. Y. ChauDetermination of Polyoxyethylene Alkylphenyl Ether Non-ionic Surfactants i nWaters-L. Favretto and F. TunisCatalymetric - Thermometric Titration of Some Derivatives of Barbituric Acid-L. s. Bark and 0. LadipoA Method for the Detection o f Microgram Amounts of Hydroxamic Acids-Shahid Abbas AbbasiA Raman Spectral Data Search System-I. A. Degen, Miss L. Birmingham and G. A.Newman161167174179187198203209212CO M M U N ICATIO N220 A Novel Approach t o the Elimination of Matrix Interferences in FlamelessAtomic-absorption Spectroscopy using a Graphite Furnace-J. G. T. Reganand J. Warren222 Book ReviewsSummaries of Papers in this lssue-Pages iv, v. viii, x-Printed by Heffers Printers Ltd, Cambridge, EnglandEntered as Second Class at New York, USA, Post Offic

ISSN:0003-2654    

DOI:10.1039/AN97601BX011

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

iv SUMMARIES OF PAPERS I N THIS ISSUE Mads, 1976Summaries of Papers in this IssueRecent Advances in the Ring Oven TechniqueA ReviewSummary of ContentsIntrodiictionThe apparatus and its useQualitative analysis of metal ionsDetermination of cations and anionsCationsAnionsOrganic substances (herbicides, vitamins, etc.)Radiochemical applicationsAir pollution studiesCombination with other analytical techniquesNew applications of the ring oven techniqueAdsorption barrierCatalysed reactionsUnstable reaction productsReprints of this Review paper can be obtained from the Publications SalesOfficer, The Chemical Society, Blackhorse Road, Letchworth, Herts., SG6 lHN,a t k1 per copy (with a 25% discount for six or more copies), post free.A remittance for the correct amount, made out to The Chemical Society,should accompany every order ; these reprints are not available through TradeAgents.HERBERT WEISZLehrstuhl fur Analytische Chemie, Chemisches Laboratorium der Universitat,78 Freiburg im Breisgau, West Germany.Analyst, 1976, 101, 152-160.Fungicide ResiduesPart V.Determination of Residues of Chloraniformethanin Grain and Cucumbers by Gas ChromatographyA method for determining residues of chloraniformethan (N-[2,2,2-trichloro-1- (3,4-dichloroanilino)ethyl]formamide) in grain and cucumbers is presented.After extraction with methanol and preliminary partitioning with hexane,chloraniformethan is extracted into dichloromethane, separated from inter-fering co-extractives by preparative thin-layer chromatography on silica geland determined by electron-capture gas - liquid chromatography.R.A. HOODLESS and M. SARGENTDepartment of Industry, Laboratory of the Government Chemist, Cornwall House,Stamford Street, London, SE1 9NQ.Analyst, 1976, 101, 161-166March, 1976 SUMMARIES OF PAPERS I N THIS ISSUEThe Determination of Chlorhydroxyquinoline in MedicatedPig FeedsPart 11. Ultraviolet Spectrophotometric Batching Assay andGas-chromatographic Assay for Mono- and Dichloro ComponentsTwo procedures have been developed for determining chlorhydroxyquinoline(halquinol) in pig feed medicated a t a level of 120p.p.m. The ultravioletspectrophotometric procedure can be used to determine halquinol and thegas - liquid chromatographic procedure to determine specifically the 5,7-dichloro- and the combined 5- and 7-chloroquinolin-8-01 components.Halquinol was found to react with copper during the initial extraction withchloroform, thus preventing formation of the silyl ether prior to gas - liquidchromatography.Partitioning the chloroform extract with dilute mineralacid so as to cause dissociation of the chelate and adding EDTA before back-extraction into dichloromethane overcame this problem.T. COWEN and W. F. HEYESSquibb International Development Laboratory, Moreton, Wirral, Merseyside.Analyst, 1976, 101, 167-173.A Simple Method for Monitoring Excessive Levels of Lead in WholeBlood Using Atomic-absorption Spectrophotometry and a Rapid,Direct Nebulisation TechniqueA method for monitoring excessive levels of lead in whole blood, using a rapid,direct nebulisation, atomic-absorption technique is described.The bloodsample is diluted with an equal volume of 0.2% m/V Triton X-100 solutionand immersed in an ultrasonic bath for 10 min. A 200-pl aliquot of theresulting solution is then nebulised and the peak height of the transientoutput pulse is monitored. Some preliminary results are also reported forcadmium and selenium in blood using the single-pulse nebulisation atomic-fluorescence technique.K. C. THOMPSON and R. G. GODDENShandon Southern Instruments Limited, Frimley Road, Camberley, Surrey,GU16 5ET.Analyst, 1976, 101, 174-178.Solvent Mediator Studies on Barium Ion- selective ElectrodesBased on a Sensor of the Tetraphenylborate Salt of the BariumComplex of a Nonylphenoxypoly(ethy1eneoxy)ethanolThe barium ion-selective electrode sensor based on the neutral carrier complexof a nonylphenoxypoly(ethy1eneoxy) ethanol containing 12 ethylene oxideunits and 2 mol of tetraphenylborate ion per mole of Ba2+ (12 EOU.Ba.2TPB)requires a more viscous solvent mediator than 4-nitroethylbenzene for long-life poly (vinyl chloride) (PVC) matrix-membrane barium ion-selective elec-trodes.Both 2-nitrophenyl octyl ether and di-2-nitrophenyl ether used inconjunction with the sensor in a PVC matrix membrane give functionalbarium ion-selective electrodes, but those with di-2-nitrophenyl ethermediator are far superior with lifetimes of about 30 d. Barium ion-selectiveelectrodes with the sensor and mediator in liquid membranes can be made fora wider range of nitro-aromatic solvent mediators.Barium ion-selective electrodes made from discs taken from a mastermembrane containing 0.40 g of a saturated solution of Antarox CO-880.Ba.-2TPB in di-2-nitrophenyl ether can be used as indicator electrodes for thepotentiometric titration of SO,2- with Ba2+. A role for a potentiometrictitration finish in the determination of sulphur in organic compounds by theoxygen-flask method is recommended.A. M. Y. JABER, G. J. MOODY and J. D. R. THOMASVChemistry Department, University of Wales Institute of Science and Technology,Cardiff, CF1 3NU.Analyst, 1976, 101, 179-186

ISSN:0003-2654    

DOI:10.1039/AN97601FP017

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

...Vlll SUMMARIES OF PAPERS I N THIS ISSUEA Semi-automated Method for the Determination ofInorganic, Organic and Total Phosphate in SedimentsMarch, 1976A simple, rapid and semi-automated method for the determination of inor-ganic, organic and total phosphorus in lake and river sediments is described.Total phosphorus is extracted from sediments with 1 N hydrochloric acid afterignition at a high temperature (550 "C) or by digestion with sulphuric acid -potassium persulphate at 135 "C in a sealed PTFE-lined Parr bomb. Organicphosphorus is determined by the difference in phosphorus content of the 1 Nhydrochloric acid extract measured before and after ignition of the drysediments a t 550 "C. In all instances the orthophosphate is determined byusing standard Technicon AutoAnalyzer I1 techniques.The interferencescaused by silica and variable acid concentrations on the determination ofphosphorus have been studied. Freedom from interferences under thechosen experimental conditions as well as the good results obtained forrecovery and precision indicate that the methods are suitable for monitoringinorganic, organic and total phosphorus in sediments.K. I. ASPILA, HAIG AGEMIAN and A. S . Y. CHAUCanada Centre for Inland Waters, Water Quality Laboratory, P.O. Box 5050, 867Lakeshore Road, Burlington, Ontario, L7R 4A6, Canada.Analyst, 1976, 101, 187-197.Determination of Polyoxyethylene Alkylphenyl Ether Non-ionicSurfactants in WatersA method is proposed for the determination of polyoxyethylene alkylphenylethers, RO(CH,CH,O),H (where R is an alkylphenyl group), at the 1-0.1 mg 1-1level in waters, The method is based on the spectrophotometric determinationof the complexes of the polyethers with the sodium cation after extractionas picrates into 1,2-dichloroethane, The number-average degree of poly-merisation (ii) is evaluated by thin-layer chromatography or by gas chro-matography.The method was tested on commercial compounds that have R = p-tert-nonylphenyl (3.3 < ii < 21.5).For typical surfactants (6.5 d ii d 21.5) theproposed method is about eight times more sensitive than that based on theammonium tetrathioisocyanatocobaltate( 11) reagent and it gives resultsfor the absolute concentration with an accuracy ranging from -6 to +8per cent. in the indicated interval of fi.The precision was evaluated fromthe analysis of waste waters. A few interferences are discussed.L. FAVRETTO and F. TUNISIstituto di Merceologia, UniversitA di Trieste, 34100 Trieste, Italy.Analyst, 1976, 101, 198-202.Catalymetric - Thermometric Titration of Some Derivatives ofBarbituric AcidThe compound barbitone, and the related compounds amylobarbitone,butobarbitone, hexobarbitone, phenobarbitone and quinalbarbitone, havebeen determined by catalymetric - thermometric titration involving an acid -base reaction in the analyte followed by a base-catalysed indicator reaction.The base-catalysed reactions used were the dimerisation of acetone and thepolymerisation of acrylonitrile with dimethylformamide as a matrix diluent.The effects of excipients are reported, and a method of assay of dosage forms isproposed.L.S . BARK and 0. LADIPORamage Laboratories, University of Salford, Salford, M5 4WT.Analyst, 1976, 101, 203-208X SUMMARIES OF PAPERS I N THIS ISSUEA Method for the Detection of Microgram Amounts ofHydroxamic AcidsMarch, 1976A simple and rapid method for the detection of trace amounts of hydroxamicacids is presented. It consists in extraction of the coloured complex formedby the reaction of hydroxamic acids (5-30 pg) with vanadium into one dropof isobutyl methyl ketone or a water-immiscible alcohol. The applicabilityof the method was tested with a variety of hydroxamic acids. It was estab-lished that carboxylic acids, their chlorides or esters, and hydroxylaminesdo not interfere.SHAHID ABBAS ABBASIDepartment of Chemistry, Indian Institute of Technology, Powai, Bombay-400 076,India.Analyst, 1976, 101, 209-211.A Raman Spectral Data Search SystemA computer-based storage and retrieval system has been devised for Ramanspectral data.. Unknown compounds can be identified by comparison oftheir spectra with the indexed library of data by means of a simple computerprogram. The method is illustrated by an example.I. A. DEGEN, hiss L. BIRMINGHAM and G. A. NEWMANResearch Division, Kodak Limited, Headstone Drive, Harrow, Middlesex, HA 1 4TY.Analyst, 1976, 101, 212-219.A Novel Approach to the Elimination ofMatrix Interferences in Flameless Atomic-absorptionSpectroscopy Using a Graphite FurnaceCommunicationJ. G. T. REGAN and J. WARRENDepartment of Industry, Laboratory of the Government Chemist, Cornwall House,Stamford Street, London, SE1 9NQ.Analyst, 1976, 101, 220-221

ISSN:0003-2654    

DOI:10.1039/AN97601BP021

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

MARCH 1976 The Analyst Vol. 101 No. 1200 100th Anniversary of The Ana/yst With this issue, No. 1200, The Analyst celebrates 100 years of continuous publication. To mark the occasion, we publish here an Editorial by Dr. F. A. Robinson, President of The Chemical Society, followed by a brief historical survey by Dr. G. W. C. Milner, President of the Analytical Division. In addition, some extracts from the first issue, published in March, 1876, are reproduced, including the title page and an introduction that sets out the original aims of the journal. Editorial The Centenary of The Analyst It is a pleasure and a privilege to be asked to contribute this Editorial to mark the Centenary of The Analyst, for I was once an analytical chemist myself, a member for 30 years of the Society of Public Analysts and Other Analytical Chemists (later the Society for Analytical Chemistry), an occasional contributor to the journal and, between the years 1938 and 1968, the writer of the bulk of the abstracts relating to biochemistry that appeared in The Analyst and subsequently in Analytical Abstracts-or so it seemed to me at the time! The Analyst underwent a great many changes both before my time and after, and has now become one of the primary journals of The Chemical Society, taking its rightful place alongside the Society’s other journals as the proper medium for the publication of original papers in the rapidly expanding field of analytical chemistry.The Analyst was originally founded “primarily, as the organ of the Society of Public Analysts and, secondly, as the representative of Analytical Chemists in general.” Its contents were by no means restricted to descriptions of analytical methods, for it also published “all cases of prosecution for adulteration, and such parliamentary and other proceedings as may appear to touch the interest of Analysts in general.” At times it must have been a very lively journal, quick to defend the interests of the new science and those who practised it, especially Public Analysts, who saw themselves as the first “Practising Chemists” in contrast to the “amateur and theoretical chemists” whom they clearly despised! In fact, however, the first “Practising Chemists” must surely have been those arch-enemies of the Public Analyst, the chemists of the Inland Revenue Laboratory at Somerset House, since this was founded in 1841, only a year after the foundation of The Chemical Society; it became eventually the Laboratory of the Government Chemist. Somerset House and the Public Analysts appear to have been inan almost perpetual state of conflict and the pages of The Analyst were frequently enlivened with editorial comments and correspondence that “displayed a command of language which many might envy today.Sarcasm, irony, hyperbole and mild invective were all employed on occasion. ” By the end of the century, however, the “Practising Chemists” obviously felt that they had established themselves, and more and more attention was given in the journal to scientific papers and abstracts. During the War of 193945 there was a revival of interest in legal matters, as a steady stream of Food Orders was issued and consideration had to be given to food standards and food substitutes.Other materials besides foods also came under the control of analysts and new techniques, such as microchemical analysis, a variety of physical methods and microbiological assays, were developed to solve new types of problems. More recently, attention has had to be directed to the detection and determination of trace amounts of, for example, metals, pesticides and medicinal chemicals, often using absurdly small amounts of sample. Such new and challenging developments inevitably led to a great expansion in research and the need to make the results available in a specialist journal. Sonow, at the end of its first 145146 CENTENARY OF THE ANALYST Analyst, Vol. 101 century, The Analyst has become one of the primary journals of The Chemical Society, with which the former Society for Analytical Chemistry amalgamated in 1975. My wish for The Analyst is that it will continue to develop in the second century of its existence with the same vigour and initiative that it displayed during its first century, and that its new status will make it better known to chemists in other fields whose own research work is likely to be helped by new developments in analytical chemistry. F. A. ROBINSON Yresiden.t, The Chemical Society

ISSN:0003-2654    

DOI:10.1039/AN9760100145

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

146 CENTENARY OF THE ANALYST Analyst, Vol. 101 The Andyst: 100 Years of Development Following the formation of the Society of Public Analysts in August, 1874, its Proceedings were first published, with the co-operation of Sir N’illiam Crookes, in Chemical News but, with the termination of that arrangement at the end of 1875, the Society resolved to publish its own journal and the first issue appeared in March, 1876, under the title it still bears today, The Analyst. The subscription price then was 3s. 6d. (17;~) per annurn, and the first issue contained 16 pages. Originally, the journal was heavily weighted towards legislative aspects of the work of Public Analysts, and for many years was concerned particularly with adulteration. Notable features of early issues were provocative and often highly critical Editorials and correspon- dence, reflecting the embryonic state of the science of analytical chemistry at that time.Over the years, the papers and the abstracts published in The Analyst have consistently reflected the developments that took place in analytical chemistry, not only as applied to foods and drugs, but also to the wider areas of water, inorganic and mineral analysis and later to bio- chemistry and related topics. In 1885, for example, the sub-title of the journal was “A monthly journal devoted to the advancement of the analysis of foods and drugs and of general analytical and microscopical research,” and the changes since then would seem amply to justify the present sub-title of “A monthly international journal dealing with all branches of analytical chemistry .” The aim of those responsible for the publication of The Analyst has always been to maintain the highest possible standards, and there is no doubt that this aim has been achieved.In the course of 100 years, many papers of fundamental importance to the development of analytical chemistry have appeared in its pages. The Reinsch test for the detection of arsenic was described by Chaston Chapman and A. H. Allen, and the Gutzeit test was described for the first time at a Society meeting; the Marsh - Berzelius test was recommended in an SPA/SCI report in 1902. In 1916, T. E. Wallis applied the microscope to quantitative analysis by employing lycopodium powder as the quantifying agent. F. Twyman, in 1920, found that many drugs showed distinctive absorption spectra and pointed out the potential of the technique for the non-destructive detection of trace amounts of active constituents, and one of the first papers on the determination of vitamins in foods was published by A.F. Watson in 1922. In the period 1924-36, a major series of 31 papers on the analytical chemistry of tantalum and niobium by W. R. Schoeller and co-workers appeared in The Analyst; the first two parts had been published in the Journal ofthe Chemical Society in 1921. With the advent of newer techniques, of major importance were the papers on partition chromatography by R. L. M. Synge (who was later awarded the Nobel Prize jointly with A. J. P. Martin for this work) in 1946 and gas chromatography by A. J. P. Martin and A.T. James in 1952. Papers on fundamental aspects are encouraged in The Analyst, and a notable example from the past is the paper on the metal complexing properties of aminopolycarboxylic acids and the analytical application of complexones published by G. Schwarzenbach in 1955. If space permitted, it would be possible to cite many other examples. The format of the journal has changed in various ways during its history, particularly when some of its contents were split off into other journals. In 1950, abstracts, which had appeared in The Analyst since its earliest years, were published separately in British Abstracts C, which had been expanding for several years, but that journal ceased publication in 1953 and the SAC inaugurated Analytical Abstracts as a new journal in 1954.In 1964, the detailed affairs of the Society, which had been published regularly in The Analyst since its inception,March, 1976 CENTENARY OF THE ANALYST 147 were removed to form the basis of another new journal, Proceedings of the Societyfor Analytical Chemistry. Other less obvious changes have involved regular revision of the layout, typo- graphy and covers so as to maintain a modern image. The Society has been concernedwith standardisation for over 50 years; in 1935 these activities were brought under the newly formed Analytical Methods Committee, and its recommended methods of analysis have appeared regularly in The Analyst. In 1952, the November and December issues were devoted to the Proceedings of the First International Congress on Analytical Chemistry, held in Oxford under the patronage of IUPAC.In 1965, the Society initiated its own conferences, and papers presented at these SAC Conferences have been a regular feature of The Analyst. In December, 1974, probably the most important issue in its history was published, containing the Centenary, Plenary and Keynote Lectures presented at the Centenary Celebrations of the Society for Analytical Chemistry. An important feature of the journal since the late 1950s has been the publication of critical reviews of various aspects of analytical chemistry, and about 60 have appeared to date. A more recent innovation has been the acceptance of brief, urgent communications on topics of immediate interest to analytical chemists, and these appear in print in as little as 5 weeks after receipt. This brief historical survey illustrates the prominent role played by The Analyst in the development of analytical chemistry over the past 100 years.During the first 99 years, its progress was fostered initially by the Society of Public Analysts and then by the Society for Analytical Chemistry but, consequent upon the amalgamation of the SAC with The Chemical Society in January, 1975, it is now one of the primary journals of The Chemical Society and has thus entered a new phase in its existence. Within such an organisation, a journal with the traditions and merits of The Analyst must continue to flourish, and it is my belief that it will continue in the forefront of analytical chemistry and in the wider field of chemistry in general, where it has such an important contribution to make. G. W. C. MILNER President, Analytical Diaision Papers from many major conferences have been published in The Analyst. The reerodzcctions on the next four pages are taken from the j r s t issue of The Analyst, published in March, 1876.

ISSN:0003-2654    

DOI:10.1039/AN9760100146

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

March, 1976 CENTENARY OF THE ANALYST 147 were removed to form the basis of another new journal, Proceedings of the Societyfor Analytical Chemistry. Other less obvious changes have involved regular revision of the layout, typo- graphy and covers so as to maintain a modern image. The Society has been concernedwith standardisation for over 50 years; in 1935 these activities were brought under the newly formed Analytical Methods Committee, and its recommended methods of analysis have appeared regularly in The Analyst. In 1952, the November and December issues were devoted to the Proceedings of the First International Congress on Analytical Chemistry, held in Oxford under the patronage of IUPAC. In 1965, the Society initiated its own conferences, and papers presented at these SAC Conferences have been a regular feature of The Analyst.In December, 1974, probably the most important issue in its history was published, containing the Centenary, Plenary and Keynote Lectures presented at the Centenary Celebrations of the Society for Analytical Chemistry. An important feature of the journal since the late 1950s has been the publication of critical reviews of various aspects of analytical chemistry, and about 60 have appeared to date. A more recent innovation has been the acceptance of brief, urgent communications on topics of immediate interest to analytical chemists, and these appear in print in as little as 5 weeks after receipt. This brief historical survey illustrates the prominent role played by The Analyst in the development of analytical chemistry over the past 100 years.During the first 99 years, its progress was fostered initially by the Society of Public Analysts and then by the Society for Analytical Chemistry but, consequent upon the amalgamation of the SAC with The Chemical Society in January, 1975, it is now one of the primary journals of The Chemical Society and has thus entered a new phase in its existence. Within such an organisation, a journal with the traditions and merits of The Analyst must continue to flourish, and it is my belief that it will continue in the forefront of analytical chemistry and in the wider field of chemistry in general, where it has such an important contribution to make. G. W. C. MILNER President, Analytical Diaision Papers from many major conferences have been published in The Analyst.The reerodzcctions on the next four pages are taken from the j r s t issue of The Analyst, published in March, 1876.March, 1976 CENTENARY OF THE ANALYST 147 were removed to form the basis of another new journal, Proceedings of the Societyfor Analytical Chemistry. Other less obvious changes have involved regular revision of the layout, typo- graphy and covers so as to maintain a modern image. The Society has been concernedwith standardisation for over 50 years; in 1935 these activities were brought under the newly formed Analytical Methods Committee, and its recommended methods of analysis have appeared regularly in The Analyst. In 1952, the November and December issues were devoted to the Proceedings of the First International Congress on Analytical Chemistry, held in Oxford under the patronage of IUPAC.In 1965, the Society initiated its own conferences, and papers presented at these SAC Conferences have been a regular feature of The Analyst. In December, 1974, probably the most important issue in its history was published, containing the Centenary, Plenary and Keynote Lectures presented at the Centenary Celebrations of the Society for Analytical Chemistry. An important feature of the journal since the late 1950s has been the publication of critical reviews of various aspects of analytical chemistry, and about 60 have appeared to date. A more recent innovation has been the acceptance of brief, urgent communications on topics of immediate interest to analytical chemists, and these appear in print in as little as 5 weeks after receipt.This brief historical survey illustrates the prominent role played by The Analyst in the development of analytical chemistry over the past 100 years. During the first 99 years, its progress was fostered initially by the Society of Public Analysts and then by the Society for Analytical Chemistry but, consequent upon the amalgamation of the SAC with The Chemical Society in January, 1975, it is now one of the primary journals of The Chemical Society and has thus entered a new phase in its existence. Within such an organisation, a journal with the traditions and merits of The Analyst must continue to flourish, and it is my belief that it will continue in the forefront of analytical chemistry and in the wider field of chemistry in general, where it has such an important contribution to make.G. W. C. MILNER President, Analytical Diaision Papers from many major conferences have been published in The Analyst. The reerodzcctions on the next four pages are taken from the j r s t issue of The Analyst, published in March, 1876.March, 1976 CENTENARY OF THE ANALYST 147 were removed to form the basis of another new journal, Proceedings of the Societyfor Analytical Chemistry. Other less obvious changes have involved regular revision of the layout, typo- graphy and covers so as to maintain a modern image. The Society has been concernedwith standardisation for over 50 years; in 1935 these activities were brought under the newly formed Analytical Methods Committee, and its recommended methods of analysis have appeared regularly in The Analyst.In 1952, the November and December issues were devoted to the Proceedings of the First International Congress on Analytical Chemistry, held in Oxford under the patronage of IUPAC. In 1965, the Society initiated its own conferences, and papers presented at these SAC Conferences have been a regular feature of The Analyst. In December, 1974, probably the most important issue in its history was published, containing the Centenary, Plenary and Keynote Lectures presented at the Centenary Celebrations of the Society for Analytical Chemistry. An important feature of the journal since the late 1950s has been the publication of critical reviews of various aspects of analytical chemistry, and about 60 have appeared to date.A more recent innovation has been the acceptance of brief, urgent communications on topics of immediate interest to analytical chemists, and these appear in print in as little as 5 weeks after receipt. This brief historical survey illustrates the prominent role played by The Analyst in the development of analytical chemistry over the past 100 years. During the first 99 years, its progress was fostered initially by the Society of Public Analysts and then by the Society for Analytical Chemistry but, consequent upon the amalgamation of the SAC with The Chemical Society in January, 1975, it is now one of the primary journals of The Chemical Society and has thus entered a new phase in its existence. Within such an organisation, a journal with the traditions and merits of The Analyst must continue to flourish, and it is my belief that it will continue in the forefront of analytical chemistry and in the wider field of chemistry in general, where it has such an important contribution to make.G. W. C. MILNER President, Analytical Diaision Papers from many major conferences have been published in The Analyst. The reerodzcctions on the next four pages are taken from the j r s t issue of The Analyst, published in March, 1876.March, 1976 CENTENARY OF THE ANALYST 147 were removed to form the basis of another new journal, Proceedings of the Societyfor Analytical Chemistry. Other less obvious changes have involved regular revision of the layout, typo- graphy and covers so as to maintain a modern image. The Society has been concernedwith standardisation for over 50 years; in 1935 these activities were brought under the newly formed Analytical Methods Committee, and its recommended methods of analysis have appeared regularly in The Analyst.In 1952, the November and December issues were devoted to the Proceedings of the First International Congress on Analytical Chemistry, held in Oxford under the patronage of IUPAC. In 1965, the Society initiated its own conferences, and papers presented at these SAC Conferences have been a regular feature of The Analyst. In December, 1974, probably the most important issue in its history was published, containing the Centenary, Plenary and Keynote Lectures presented at the Centenary Celebrations of the Society for Analytical Chemistry. An important feature of the journal since the late 1950s has been the publication of critical reviews of various aspects of analytical chemistry, and about 60 have appeared to date.A more recent innovation has been the acceptance of brief, urgent communications on topics of immediate interest to analytical chemists, and these appear in print in as little as 5 weeks after receipt. This brief historical survey illustrates the prominent role played by The Analyst in the development of analytical chemistry over the past 100 years. During the first 99 years, its progress was fostered initially by the Society of Public Analysts and then by the Society for Analytical Chemistry but, consequent upon the amalgamation of the SAC with The Chemical Society in January, 1975, it is now one of the primary journals of The Chemical Society and has thus entered a new phase in its existence. Within such an organisation, a journal with the traditions and merits of The Analyst must continue to flourish, and it is my belief that it will continue in the forefront of analytical chemistry and in the wider field of chemistry in general, where it has such an important contribution to make. G. W. C. MILNER President, Analytical Diaision Papers from many major conferences have been published in The Analyst. The reerodzcctions on the next four pages are taken from the j r s t issue of The Analyst, published in March, 1876.

ISSN:0003-2654    

DOI:10.1039/AN9760100148

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

152 Analyst, March, 1976, Vol. 101, pp. 152-160 Recent Advances in the Ring Oven Technique A Review* Herbert Weisz Lehrstuhl fur Atzalytische Chemie, Chemisches Labovatoriunz der Universitict, 78 Freiburg im Breisgazc, West Germany Summary of Contents Introduction The apparatus and its use Qualitative analysis of metal ions Determination of cations and anions Cations Anions Organic substances (herbicides, vitamins, etc.) Radiochemical applications Air pollution studies Combination with other analytical techniques New applications of the ring oven technique Adsorption barrier Catalysed reactions Unstable reaction products Introduction The first paper on the ring oven technique was published in 1954.l This technique is basically a special type of spot analysis carried out on filter-paper in which, however, the substances to be identified or determined are concentrated in the form of sharply developed, well defined circular lines as a result of the heat-barrier action of the edge of the central bore-hole of the heating block of the ring oven.Originally, this method was devised as a separation tech- nique for extremely minute samples (e.g., in investigations of works of art). From the two basic aspects-the concentration of substances on filter-paper in the form of well defined lines and the possibility of carrying out separations on a single drop-all of the applications of this technique in many fields that have since been published in more than 300 papers were derived. In 1961 a monograph, “Microanalysis by the Ring Oven Technique,” was published and in 1970 the Second Edition2 appeared (subsequently referred to in this paper as the mono- graph) in which all of the then known applications of the method were surveyed.Since then, about 100 further publications dealing with the ring oven method have been published. Most of them are discussed in this review, although some can be mentioned only very briefly. The Apparatus and Its Use The basic form of the ring oven itself has not been altered since its first development. The ring oven is usually made of aluminium, but various other metals have been used. In the monograph2 ring ovens made of glass are mentioned. Within the last few years, similar glass ring ovens have been described by Chiba3 and co-workers; one of them is a portable oven, obviously designed for field ~ o r k .~ - ~ The “Nichrome-wire ring chamber” of Hashmi et aZ.7 is a glass ring oven with a heating wire installed in it, in a manner similar to that in the usual metal ring ovens. Improvised home-made ring ovens that are simple and inexpen- sive have also been described.8~~ Instead of the edge of the hot ring oven for concentrating substances on filter-paper in narrow zones, a brief mention has been made of the possibility of using a hot stream of air10 or nitrogen11 for the purpose of providing a “heat barrier.” The dependence on the quality of various filter-papers of the limits of identification in several reactions for anions has been investigated.12 * Reprints of this review will be available shortly. For details, see summaries in advertisement pagesWEISZ 153 Gertner and GrdiniC carried out some theoretical investigations on the process of pre- cipitation, complexing and transporting ions to the ring 2one.l3-l5 Autoradiography has been used in a number of these experiments (e.g., using labelled silver ions).13J6 The deter- mination of the solubility of poorly soluble silver salts (such as halides, phosphate, sulphide and chromate) on filter-paper has been carried out using ring oven colorimetry; it has been found that solubilities are much lower on paper than directly in water.16 Ackermann and Gressmann had already made similar studies some time ag0.l’ By using the same technique, the solubilities of a number of other salts (eg., sulphides of various metals) have likewise been investigated.l8 Qualitative Analysis of Metal Ions Identification reactions for almost all metal ions have been adapted for use with the ring oven method, but it is beyond the scope of this review to record all of the new developments that have been described in recent years.For some of them, unfortunately, not enough detailed information has been provided (e.g., identification limits, interferences, precise reaction conditions). Many of the reactions used for quantitative analysis can also be applied for qualitative purposes ; therefore, the reactions mentioned in the following section should also be considered from the viewpoint of qualitative analysis. The identification of a number of metals using the fluorescence of their morinates has been described, beryllium and aluminium having already been identified with morin (2‘,3,4’,- 5,7-pentahydro~yflavone)~; the reactions of arsenic, calcium, caesium, lanthanum, lead, lithium, magnesium, strontium and zinc are described, although several of the reactions have poor identification limits (e.g., caesium and arsenic, 15 pg).l9 A brief study on the sensitivity of detection of some metals, alone and in defined mixtures, has been carried out.20 Ghose and Dey devised systematic separation schemes for 20 common metalsz1 and for fourteen “less common” metals (gold, beryllium, thallium, cerium, titanium, zirconium, thorium, vanadium, molybdenum, tungsten, uranium, selenium, tellurium and platinum) ,23 by combining solvent-extraction procedures and the ring oven ; some further examples of extraction procedures can be found in the monograph.z Two analytical schemes for all six platinum metals, using solvent extraction directly on the filter-paper, have been published r e ~ e n t l y .~ ~ , ~ * An example of the application of potass- ium thiocarbonate as a reagent for the separation of metal ions is provided by a systematic scheme for 20 common metals.25 The separation of some metals using dithiooxamide, and a study on the separation efficiency by use of radioactive isotopes of the corresponding metal ions (silver, cobalt, zinc, iron, barium), have been described.26 Du and Gutbier described an interesting scheme for the simultaneous separation of some anions (SO,”, C1-, NO3-) and cations (iron, nickel, aluminium, cadmium, copper) ; a ring oven with three different bore-hole diameters (17, 22 and 28 mm) was used.27 To close this section, two practical applications of the ring oven method can be mentioned.Locke and Riley (Guggenheim Museum, New York) published a systematic scheme for the analysis of paint samples from valuable paintings.28 This work is of particular interest to the present author, because more than 20 years ago the ring oven technique was originally devised with investigations of objets d’art in mind. A number of such applications to metal specimens can be found in the monograph.2 Thomas and Lee used the ring oven method for the analysis of trace amounts of metal particles (iron, zinc, manganese) in intravenous solutions (injections) .29 Determination of Cations and Anions The comparison of the colour intensities of unknown rings with those of standard rings, a procedure that has been called “ring colorimetry,” has found many applications in the analysis of metal ions, anions and organic substances. In fact, most papers on the ring oven technique deal with the quantitative aspects of the method.It should be mentioned that there has been some discussion about whether “semi-quantitative” or “quantitative” is the most appropriate description for ring colorimetry. West30 may be quoted here: “If the ring oven is semi-quantitative at these levels then so are such methods as polarography, emission spectroscopy and colorimetry.” In this connection, it might be of interest that some workers have compared results achieved by the ring oven method with results obtained154 WEISZ: RECENT ADVANCES I N Analyst, Vol.101 by other well established analytical techniques, such as polarography,3 spectrophotometry5~31 and atomic-absorption spectro~copy~+~~ ; in all instances the results were in good agreement. Cations Table I lists newer applications of the ring oven method to the determination of metal ions. In the method for manganese,35 the resulting benzidine blue is not very stable and changes In order to obtain a series of permanent standard rings for comparison, a colour with time. coloured crayon of a suitable colour (matching that of benzidine blue) was used. TABLE I DETERMINATION OF METAL IONS Ion Reaction Reference Mn Be Cd c u Fe V Se Ca Pb Pb Pb Pb Benzidine Morin (crayon) in W Bathocuproin Bathophenanthroline Schiff base (anthranilic acid + salicylddehyde) 2,3-Diaminonaphthalene in UV Di( 2-hydroxyphenylimino) ethane Potassium chromate Dithizone As [PbC1,I2- in UV Molybdate 3 molybdenum blue [Fe(%~’-bPY)sl [CdI,I 36 36 37 3 3 39 40 33, 41 32 42 43 38 In the determination of beryllium with morh, West and J u n g r e i ~ ~ ~ used a crayon in which the morin is incorporated in a suitable solid medium (monoglyceryl stearate and paraffin wax) instead of a reagent solution.A number of other morinates have likewise been used for the determination of the corresponding metals ; the qualitative applications of these marinates have been cited above.19 Fluorescent iron morinate rings have been used as a common standard scale for the determination of several metals (iron, copper, cobalt, nickel, manganese).44 This is a further example of the possibility of using a universal standard scale instead of preparing an individual standard scale for every substance to be determined.Earlier examples can be found in the monograph.2 The determination of platinum metals had been described, but unfortunately without sufficient detail~.~4 The rapid separation and determination of uranium(V1) using DEAE-cellulose anion- exchange paper and potassium hexacyanoferrate(I1) has been described.45 Johri and co-workers developed three practical applications for ring colorimetry, namely the determination of arsenic in animal feeds (utilising the reaction As2S3.-+Ag,S),46 calcium in mineral waters40 and some trace metals (iron, zinc, manganese, copper) in milk.47 Du and Gutbier48 determined trace amounts of copper in nickel and cobalt salts with dithiooxamide, first using a spot of lead sulphide on the paper in order to locate the trace metal, Many other determinations have been carried out in connection with air pollution studies, and are considered later.In a number of papers, further examples of the combination of thin-layer and paper chro- matography with the ring oven technique have been discussed: various groups of metals (e.g., the six platinum metals,49 other noble metals50 and alkali metals51) are separated by one of the two chromatographic techniques and are then dissolved from the chromatographic support using methods described in the monograph2 and determined with the aid of suitable ring colorimetric methods. In some instances, previously known methods are used for the final determination, while in some of the papers insufficient information is provided.52-58 The question of whether photometric measurement of the intensity of the rings could make ring colorimetry more accurate was considered long ago; the monograph2 (p.71) should be consulted on this point. Recently, two contributions have dealt with this possibility again: Friedrichs and Grover59 evaluated the intensity of the rings by light reflectance measurement for the determination of iron as Prussian blue in air pollution studies; Du et aZ.60 measured the light absorption of the rings, cellulose acetate filters being used instead of ordinary filter- paper. In order to achieve even better transparency of the supporting matrix, the filters were moistened with paraffin oil before the final photometric measurement, and in this wayMarch, 1976 THE RING OVEN TECHNIQUE 155 iron (Prussian blue), nickel (dimethylglyoxime) and copper (benzoin a-oxime) were deter- mined with the aid of a microscope photometer.A completely new approach to quantitative determinations, the use of catalysed reactions and of unstable reaction products, is discussed later under New Applications of the Ring Oven Technique. Anions Very little can be reported about new contributions to the determination of anions. West et aL61 determined sulphuric acid in air pollution studies. Potassium bromide is washed to the ring zone together with the acid, sodium fluorescein and potassium bromate is being added to the ring zone.The red eosin ring formed is compared with a standard scale. By this method, total protons can be measured likewise by adding all three reagents at once to the centre sample spot and transferring the eosin formed to the ring zone, Phosphate, silicate, arsenate and germanate have been determined with the aid of the well known molybdenum - benzidine blue reactioms2 Because all four of these ions form hetero- poly acids with molybdate, all of which can be converted into benzidine blue, a common standard scale can be applied; this is also an example of a “universal standard scale.” A few other methods for the determination of anions are considered in the last section of this review. Organic Substances (Herbicides, Vitamins, etc.) Although the ring oven method has found many applications with inorganic substances, the number of analytical applications with organic substances is still rather limited; it is to be hoped that future developments will result in more applications in this area, perhaps with the aid of the newly developed adsorption barrier technique (see the last section).In addition to the examples of alkaloids already mentioned in the monograph,2 some further determinations of this group of substances have been reported. Shah and Hussains3 deter- mined ajmaline with P-dimethylaminobenzaldehyde in a number of pharmaceutical products. Chibas reported the detection and determination of some alkaloids (morphine, codeine, cocaine, caffeine, quinine, ephedrine, strychnine and papaverine) by the ring oven technique, mostly using suitable known colour reagents, e.g., picric acid, iron(II1) chloride, molybdo- phosphoric acid, molybdate and hexacyanoferrate( 11).Ergosterol has been determined with 2,3,5-triphenyltetrazolium chloride and potassium hydroxide, forming a red reaction product that was stabilised with copper nitrate (0.03-1 pg , ~ l - l ) . ~ ~ In the monograph,2 some methods are mentioned for determining a number of insecticides. The first application of the ring oven technique to herbicide analysis was described by toha and VojinoviP5; amiben was determined by spraying the rings first with sodium nitrite, followed by N-1-naphthylethylenediamine dihydrochloride (red), while diquat and paraquat rings were made visible with methanolic sodium hydroxide solution (brown and bluish green, respectively).Coha and Klj a j i P subsequently described the separation of five herbicides (amiben, paraquat, diquat, CDAA and CIPC) by thin-layer chromatography, followed by their determination. The extraction of trace amounts of the herbicides diquat and paraquat from water and soil, using column chromatography on a cation-exchange resin for their separation and the ring oven technique for their determination, was described by toha?’ It is certainly of great interest to provide methods for determining small amounts of pesticides now that environmental problems are becoming increasingly important. Several fats and oils of mineral and vegetable origin have been determined, using the phenomenon that these substances render filter-paper translucent.These translucent rings are always compared with the corresponding translucent standard scale prepared with hard paraffin wax.88 Hashmi and co-workers described the determination of a number of organic substances, e.g., amino-acid~~~ and vitamins,70 with the “Nichrome-wire ring chamber,’’ using a somewhat different approach (“sensitivity scale”) that had previously been discussed in principle by Wenger et al. (“extinction method”).71 Radiochemical Applications The application of the ring oven method to radiochemical analytical procedures has been discussed extensively in the monograph2 and here only some of the newer developments are156 WEISZ: RECENT ADVANCES IN Analyst, Vot. 101 mentioned. The use of radioactive tracers for the study of precipitation, complexing reactions and for following the efficiency of separations on filter-paper have already been mentioned above in the sections on The Apparatus and Its Use13J4J6 and Qualitative Analysis of Metal Ions .26 Klockow and co-workers carried out a series of studies on radiochemical separations by the ring oven technique.The genetically related radionuclides cerium-144 and praseodymium- 144 could be separated on filter-paper impregnated with hydrated manganese oxides ; the praseodymium-144 is transferred to the ring zone with trichloroacetic acid, whereas the cerium-144 remains in the centre of the filter-paper; a carrier-free solution of cerium-144 was a~plied.7~ Silver-109m could be separated from its parent nuclide cadmium-109 on carboxymethylcellulose paper using thiosulphate as a complexing agent for the silver.For the separation of cadmium-109 from a silver matrix, another possibility was described.'3 The silver is retained on paper impregnated with copper(I1) sulphide and the cadmium (together with released copper ions) is washed into the ring zone with acetic acid.73 The selective isolation of caesium-137, zirconium-95 - niobium-95, ruthenium-106 and yttrium-90 plus cerium-144 - praseodymium-144 from a mixture containing long-lived fission products has been reported.74 Suitable combinations of impregnated filter materials and solvents with and without complexing agents were applied. Kri~Afi'~ published a method for the determination of copper in the presence of several other metals involving the release of radioactivity through an exchange reaction. A spot of cadmium sulphide, labelled with cadmium-109, is prepared in the centre of a filter-paper, the test solution (copper) is added and an amount of cadmium equivalent to the copper present is released and transferred to the ring zone The activity of the radioactive cadmium in the ring is measured.If a standard amount of copper is treated likewise, it is easy to calculate the amount to be determined from the ratio of the two measured activities. This method is generally applicable and should permit the determination of a number of other metal ions. Air Pollution Studies The ring oven method has been used very frequently in recent years to study and control air pollution. This question has been discussed particularly in two recent books76J7 and in some summarising papers (e.g., reference 8).In the monograph,2 contributions to this special field up to 1970 are cited. Samples collected by impaction or electrostatic precipitation can be dissolved and drops of the solution obtained can be subjected to the usual ring oven procedures. In most in- stances, however, samples of airborne particulate matter are collected on filter-paper or other suitable filter media (membrane filters, glass-fibre filters, etc.). When a filter-paper is applied as the collecting medium, the sample collected can be concentrated directly into the ring zone and made visible there for comparison purposes. If the samples are collected on other filtration media, they must be transferred on to ordinary filter-paper and concentrated there.These methods for the transfer, concentration and determination of collected air- borne particulate matter are described extensively in the monograph2 and in an earlier publication. 78 If the collected sample is washed directly on the ring oven into the ring zone, only one ring is available for the comparison instead of the usual three rings in ring colorimetry, and this is accepted in many published practical examples. A possible means of obtaining three rings is to dissolve the collected sample in a suitable solvent and to prepare three sample rings, but much more of the material to be determined needs to be collected than is actually used in preparing the three rings. We proposed some time ago an alternative procedure,79 in which three circular pieces of different but well defined sizes are cut from the filter used for sampling, the areas of the three cuttings being in a suitable ratio to each other, and the collected material is transferred from these small pieces to the ring zones of three separate filter-papers, thus giving three rings (corresponding to three rings with different known drop numbers). This procedure was verified by Chiba in the determination of nickel and copper in air.5131 In Table 11, most of the determinations of polluting material by the ring oven method known to date are summarised.Table I1 lists not only newer contributions but also deter- minations that were mentioned in the monograph2 in order to present as complete as possible a survey of this field of analysis.March, 1976 THE RING OVEN TECHNIQUE 157 Chinese workers have discussed the determination of phosphorus , sulphur, selenium , mercury, lead and cadmium in air,89 but unfortunately no information on the details of the methods used is available to the reviewer.An investigation on water pollution has been described,34 copper, cadmium and zinc being determined after their concentration by extraction procedures. TABLE I1 DETERMINATION OF AIRBORNE PARTICULATES Ion Reaction Sb Molybdophosphoric acid cu Dithiooxamide crayons cu Bathocuproin Pb Molybdate + diphenylcarbazide Pb Chromate Pb Dithizone Pb As [PbC141a- in UV Fe Potassium hexacyanoferrate(I1) Fe Potassium hexacyanoferrate( 11) (reflectance) Fe Bathophenanthroline Al Morin Mn Benzidine Ni Dimethylglyoxime Zn o-Mercaptothenalaniline crayons Be Morin crayon Se 3,3’-Diaminobenzidine PO4*- o-Dianisidine molybdate PO4*- Molybdate + benzidine H,SO, Sulphur Caffeine Acetylacetone + pdimethylaminobenzaldehyde Cd [Fe(~,.’-bPY)sl[CdI,1 so SO:a- 2- }BaCI, + KMnO, + oxalic acid (co-precipitation) Br0,- + Br- + fluorescein Copper(1) sulphate +- colloidal Cu,S Reference 80 81 5 37 43 33, 41 32 42 78 69 4 78 35 31 82 36 83 84 85 86 61 87 88 Combination with Other Analytical Techniques The combination of electrographic sampling, involving anodic dissolution of metals, with the ring oven technique was described by Stephen.so Two more recent papers on this com- bination of techniques for the analysis of various alloys have been publi~hed.91~~~ Combinations with chromatographic techniques have already been mentioned in this review for mixtures of metal ions4s-53~ 55-58 and for organic substances (herbicides).66 As an example of the combination with circular chromatography, Frei and Stockton93 developed a method for the determination of trace metals (cobalt, copper, iron, nickel) in natural samples (tap water, sea water, algae).The use of ion exchange in connection with the analysis of metal i0ns,4~ herbicides67 and radioactive ~ u b s t a n c e s ~ ~ ? ~ ~ has already been mentioned in other sections of this review. As a further example of the combination with titrimetric analysis, the complexometric titration of aluminium after its separation from other metals by the ring oven method has been des~ribed.~~ The ring oven technique has been used to concentrate metal samples (silver, palladium, rhodium, platinum, gold, copper, iron) on filter-paper for X-ray fluorescence analysis, giving higher sensitivities in the determination of these metakS5 New Applications of the Ring Oven Technique Adsorption Barrier All of the applications of the ring oven method that have been described so far are based on the use of a heat barrier, and substances that are not sufficiently stable at the temperature of the heating block cannot be analysed.A means of avoiding this difficulty while still being able to concentrate substances in a narrow outlined ring zone is to use an adsorption barrier instead of a heat barrier, the ring oven itself being used only for the preparation of a158 WEISZ : RECENT ADVANCES IN Analyst, Vol.101 narrow ring zone, consisting of a suitable adsorbent. The actual separation and concentration of the sample are carried out on this prepared filter-paper without the heated ring 0ven.~6~~7 In an example of this technique, blood peroxidase was washed fiom the centre of a filter- paper with sodium chloride solution on to a magnesium hydroxide adsorption barrier, where the enzyme was retained; a sharply outlined blue ring appeared on spraying the filter-paper with benzidine - hydrogen peroxide - acetic acid solution. It now seems to be possible to apply the ring oven technique to biological specimens; preliminary work in our laboratory has given promising results. A number of binary mix- tures of dyestuffs have been separated on the basis of their different adsorption behaviour on various adsorbents (aluminium, magnesium and beryllium hydroxides) .98 These anions release chloranilate from a lanthanum chloranilate spot prepared in the middle of a filter-paper that also bears an adsorption barrier ring consisting of aluminium and magnesium hydroxides.The chloranilate released, which is not stable to heat and would otherwise change colour, is transferred to the adsorption zone with methyl Cellosolve; a violet ring appears.9g This technique has also been used for the determination of fluoride and oxalate. Catalysed Reactions Tests based on the use of catalysed reactions are very sensitive, because the final product to be observed is not the result of a stoicheiometric reaction between the reagent and the substance to be identified; the latter serves only as a catalyst and, consequently, a much greater amount of the end-product is formed.If the catalyst to be identified is concentrated in the form of a sharply outlined ring zone, such reactions can be made even more sensitive. Some catalysed identification reactions have been describedloO in which the catalyst is washed into the ring zone together with one of the reactants and sprayed with the second reactant. It is not practicable to apply the same technique to semi-quantitative determinations because the amount of reaction product formed is obviously dependent on the time that has elapsed since the start of the reaction, which makes it impossible to use a stable standard scale. The observation of simultaneously started catalysed reactions with unknown and known concentrations of the catalyst enabled us to apply such reactions to the determination of catalysts.This is, in effect, an application of the “simultaneous comparison method” to the ring oven techniquelOl: one drop of the unknown catalyst sample solution and of two different standard solutions are spotted at three concentric points around the middle of a round filter-paper, thus forming an equilateral triangle. These three drops are washed in the usual manner on the ring oven from the centre to the ring zone; the three different amounts of the catalyst are thereby concentrated in the form of three sharply outlined circular seg- ments. The filter-paper is then sprayed with a solution of the two reactants of the catalysed reaction and the changes in colour in the three segments are observed.The order of these changes shows whether the concentration of the sample is higher or lower than the two standard concentrations or if it lies between them. In further steps, the sample drop and two drops of suitably chosen standard solutions (six different standard concentrations are sufficient) are placed on a new filter-paper and the whole procedure is repeated. In most instances, after the third comparison step one can establish the standard concentration to which the unknown concentration corresponds best. For higher accuracy it is advisable to carry out a second determination with a different number of drops of the unknown solution. Several catalysts have been determined in this manner, e.g., vanadium (p-phenetidine + bromate) , molybdenum (iodide + hydrogen peroxide), copper (fi-phenylenediarnine + hydrogen peroxide), cobalt (pyrocatechol + hydrogen peroxide), silver (Leucomalachite Green + S,O,2-), L-cystine (iodine - azide reaction).Hexacyanoferrate( 11) inhibits the catalytic action of cobalt in the above reaction and so can be determined indirectly.lo2 It is possible to apply this technique to the determination of some enzymes.97 Unstable Reaction Products If a chemical reaction yields coloured products that are unstable, it cannot be used in ring colorimetry in the usual way because it is impossible to have a stable standard scale. The “segment technique” mentioned above offers the possibility of using even reactions such asMarch, 1976 THE RING OVEN TECHNIQUE 159 these in ring colorimetry. The technique is the same as described above; in catalysed re- actions, products are formed that change with time, Le., that are also unstable.In this instance also, six standard solutions are used instead of a standard scale. A number of methods for direct and indirect determinations in this manner have been described, e.g., iron (thiocyanate), vanadium (3,3'-dimethylnaphthidine) , chromate (o-tolidine) and formal- dehyde (o-dianisidine). Lead and EDTA were determined indirectly by using the reaction of chromate with o-tolidine.103 Nanogram amounts of nitrate and nitrite have been determined alone and in admixture by this method with the well known Griess - Ilosvay reaction; nitrate has first to be reduced on a zinc-coated iron plate.lo4 1.2. 3. 4. 5. 6. 7. 8. 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. 63. References Weisz, H., Mikrochim. Acta, 1954, 140. Weisz, H., “Microanalysis by the Ring Oven Technique,” Second Edition, Pergamon Press, Oxford, Chiba, A., and Ogawa, T., Bunseki Kagaku (Japan Analyst), 1972, 21, 303. Chiba, A., Bunseki Kagaku (Japan Analyst), 1973, 22, 21. Chiba, A., Bunseki Kagaku (Japan Analyst), 1974, 23, 237. Chiba, A., Ansen Kogaku, 1973, 12, 112. Hashmi, M. H., Shahid, M. A., Chughtai, N. A., and Rana, M. A., Mikvochim. Acta, 1968, 1143. West, P. W., and Sachdev, S. L., J .Chem. Educ., 1969, 46, 96. Herrera, N. M., and Laux, C. D., J . Chem. Educ., 1973, 50, 756. Ronneau, C. J. M., Jacob, N. M., and Apers, D. J., Analyt. Chem., 1973, 45, 2162. Moskaliuk, K., MarjanoviC, V., Maiuranovid, K., GoluboviC, A., and ESkinja, I., Mikrochim. Actu, Ackermann, G., and Gressmann, K., Mikrochim. Acta, 1970, 662. Gertner, A., and GrdiniC, V., Mikrochim. Acta, 1975, I, 197. GrdiniC, V., and Gertner, A., Mikrochim. Acta, 1975, I, 205. GrdiniC, V., Mikrochim. Acta, 1975, I, 425. GrdiniC, V., Mikrochim. Acta, 1975, I, 253. Ackermann, G., and Gressmann, K., Mikrochim. Ada, 1966, 4 . GrdiniC, V., and Gertner, A., Acta Pharm. Jugosl., 1973, 23, 95; Analyt. Abstr., 1973, 25, 2135. Gertner, A., Kodrnja, D., Pavisid, D., and GrdiniC, V., Acta Pharm. Jugosl., 1971, 21, 125.Soloniewicz, R., and Teodorczyk, M., Rudy Metale Niezel., 1974, 19, 576; Chem. Abstr., 1976, 82, Ghose, A. K., and Dey, A. K., Analyst, 1970, 95, 698. Ghose, A. K., and Dey, A. K., Separ. Sci., 1967, 2, 673. Agrawal, B. K., Ghose, A. K., and Agarwala, B. V., Separ. Sci., 1973, 8, 413. Kaushik, N. K., and Mehra, H. C., Talanta, 1974, 21, 790. Johri, K. N., and Singh, K., Mikrochim. Acta, 1970, 1. GrdiniC, V., Tabor, Z., and Gertner, A,, Mikrochim. Acta, 1976, I, 433. Du, Ngo Huy, and Gutbier, G., Mikrochim. Acta, 1972, 935. Locke, D. C., and Riley, 0. H., Stud. Conserv., 1970, 15, 94. Thomas, W. H., and Lee, Y. K., Acta Pharm. Suec., 1974, 11, 495; Analyt. Abstr., 1975, 28, 6E2. West, P. W., Analyt. Chem., 1968, 40, 143R. 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I., and Chughtai, M. I. D., Mikrochim 71. Wenger, P. E., Monnier, D., and Piguet, A., Helv. Chim. Acta, 1946, 29, 1698. 72. Klockow, D., and Bohmer, R. G., Talanta, 1969, 16, 1209.73. Klockow, D., and Krivbii, V., Radiochem. Radioanalyt. Lett., 1969, 2, 181. 74. Klockow, D., and Abe, S., Radiochem. Radioanalyt. Lett., 1970, 4, 237. 75. Krivbii, V., Talanta, 1969, 16, 1513. 76. West, P. W., in Stern, A. C., Editor, “Air Pollution,” Volume 11, Academic Press, New York, 1968, 77. Gallay, W., “Environmental Pollutants : Selected Analytical Methods,” Butterworths, London, 1975. 78. West, P. W., Weisz, H., Gaeke, G. C., and Lyles, G., Analyt. Chem., 1960, 32, 943. 79. Weisz, H., Talanta, 1964, 11, 1041. 80. West, P. W., and Llacer. A. J., Analyt. Chem., 1962, 34, 555. 81. West, P. W., and Pitombo, L. R. M., Analytica Chim. Acta, 1967, 37, 374. 82. West, P. W., and Thabet, S. K., Analytica Chim. Acta, 1967, 37, 246. 83. West, P. W., and Cimerman, Ch., Analyt. Chem., 1964, 36, 2013. 84. West, P. W., and Sachdev, S. L., “Atmospheric Environment,” Volume 2, Pergamon Press, Oxford, 85. Rayner, L. W. W., Mikrochim. Acta, 1970, 214. 86. Huygen, C., Mikrochim Acta, 1963, 6. 87. Rowland, R., and West, P. W., Analytica Chim. Ada, 1972, 61, 162. 88. Ordoveza, F., and West, P. W., Analytica Chim. Acta, 1964, 30, 227. 89. Chang, Tsu-Chun, Huaxue Tongbao, 1974, 2, 26; Analyt. Abstr., 1974, 27, 2266. 90. Stephen, W. I., Mikrochim. Acta, 1956, 1531. 91. Armeanu, V., and Niculescu, I., Revue Roum. Chim., 1971, 16, 1867; Analyt. Abstr., 1972, 23, 1462. 92. Johri, K. N., and Handa, A. C., Microchem. J . , 1973, 18, 491. 93. Frei, R. W., and Stockton, C . A., Mikrochim. Acta, 1969, 1196. 94. Gertner, A., and GrdiniC, V., Acta Pharm. Jugosl., 1970, 20, 187; Analyt. Abstr., 1971, 21, 982. 95. Ackermann, G., Koch, R. H., Ehrhardt, H., and Sanner, G., Talanta, 1972, 19, 293. 96. Weisz, H., and Abe, S., Mikrochim. Actu, 1970, 1054. 97. Weisz, H., Proc. SOG. Analyt. Chem., 1974, 11, 319. 98. Abe, S., and Kikuchi, H., Mikrochim. Acta, 1973, 615. 99. Abe, S., and Kikuchi, H., Mikrochim. Acta, 1975, I, 379. 100. Weisz, H., and Kiss, T., Bull. SOC. Chim. Beograd, 1969, 34, 419. 101. Bognar, J., Mikrochim. Acta, 1963, 397. 102. Weisz, H., Pantel, S., and Vereno, I., Mikrochim. Acta, 1975, 11, 287. 103. Weisz, H., Pantel, S., and Vereno, I., Mikrochim. Acta, in the press. 104. Weisz, H.. and Hanif, M., Analytica Chim. Acta, in the press. Acta, 1969, 36. p. 147. 1968, 331. Received October 22nd, 1976 Accepted November 6th, 1976

ISSN:0003-2654    

DOI:10.1039/AN9760100152

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

Analyst, March, 1976, Vol. 101, pp. 161-166 161 Fungicide Residues Part V.* Determination of Residues of Chloraniformethan in Grain and Cucumbers by Gas Chromatography R. A. Hoodless and M. Sargent Department of Industry, Laboratory of the Government Chemist, Cornwall House, Stamford Street, London, SEl9NQ A method for determining residues of chloraniformethan {N-[2,2,2-trichloro- 1- (3,4-dichloroanilino) ethyl] f ormamide} in grain and cucumbers is presented. After extraction with methanol and preliminary partitioning with hexane, chloraniformethan is extracted into dichloromethane, separated from inter- fering co-extractives by preparative thin-layer chromatography on silica gel and determined by electron-capture gas - liquid chromatography. Chloraniformethan {N-[2,2,2-trichloro-1-(3,4-dichloroaniLino)ethyI]forma~de~ is a recently introduced systemic fungicide.lY2 In the United Kingd~m,~ recommendations have been issued for its safe use on cereals and hops and, provisionally, on leaf brassicas, swedes and turnips.It is included in the list of Approved Products and Their Uses for Farmers and Growers* as a protection of barley and roses against powdery mildew. Its use on cucumbers has also been r e p ~ r t e d . ~ ~ ~ The only published method for residue analysiss is based on the hydrolysis of chlorani- formethan to give 3,4-dichloroaniline, which is determined colorirnetrically by diazotisation and coupling with 2-aminoethyl-l-naphthylamine. This method does not enable chlorani- formethan to be distinguished from several other widely used pesticides that also yield dichloroaniline on hydrolysis.In the method described below, thin-layer and gas chromato- graphy are used for the determination of chloraniformethan at residue levels. Fortified samples of barley, wheat and cucumber were used to obtain the results for re- covery recorded here. Experimental The work was carried out on samples with unknown history, all recovery tests being made on artificially fortified chopped samples. The samples were extracted with methanol using either a homogeniser or a Soxhlet extraction apparatus. The extracts were diluted with water and given a preliminary wash with hexane in order to remove some of the highly coloured co-extractives. Partitioning into dichloromethane was used so as to provide a concentration step, followed by clean-up on preparative thin-layer chromatographic plates and determination by gas - liquid chromatography with an electron-capture detector. Chloraniformethan is relatively involatile but appears to be unstable at temperatures above about 200 "C.Thermal analysis showed a slow loss of mass between about 200 and 300 "C, indicating slow decomposition, followed by a more rapid loss above 300 "C as vapori- sation of the decomposition products occurred. Its reproducible gas-chromatographic determination thus presents some difficulty. The most satisfactory results were obtained with a column of 5% neopentyl glycol succinate on Gas-Chrom Q operated at 180 "C. This column gave a sharp, symmetrical peak for chloraniformethan, which was reproducible provided that care was taken to avoid conditions that favour decomposition (use of clean silanised glass columns and clean sample extracts and avoidance of contamination of the stationary phase, particularly in the injection region of the column). It was not possible to confirm the identity of the gas-chromatographic peak by mass spectrometry as the chloraniformethan appeared to be lost or had decomposed either at the silicone rubber gas-chromatographic - mass spectrometric interface or in the heated metal * For Part IV of this series, see Analyst, 1976, 100, 249.Crown Copyright.162 Analyst, VuZ. 101 transfer line. However, it seems probable that when decomposition occurs, a major residual product under these conditions would be 3,4-dichloroaniline.With the standard gas- chromatographic conditions used in the method, chloraniformethan gave a main peak a t 8.3-min retention time with very small peaks at 0.3, 0.5, 1.0, 3.0, 6.1 and 6.7 min, whereas 3,4-dichloroaniline has a retention time of 6.0min. During preliminary work and while attempting to obtain satisfactory chromatograms using different column packings and higher injection temperatures, a major peak with the same retention time as 3,4-dichloroaniline was observed. The gas-chromatographic determination of chloraniformethan could be applied to sample extracts only after a rigorous clean-up. It was found that column chromatography gave a "clean" sample, as indicated by the electron-capture detector, but remaining co-extractives still interfered, apparently by causing breakdown on injection. Silica gel, alumina and poly- amide columns were tried with a variety of eluting solvents without success.Preparative- scale thin-layer chromatography was found to give a much better clean-up without undue difficulty and also greatly facilitated the separation of chloraniformethan from other poten- tially interfering pesticides. A range of different commercially available pre-prepared thin-layer chromatographic plates was tested. Silica gel was chosen because it gave narrower bands and (with some sample extracts) lower levels of background material than alumina, cellulose or polyamide layers and was much easier to handle during the quantitative appli- cation and removal of samples; a 1000-pm thick layer gave the best compromise between sample capacity and ease of use.Calcium sulphate was a satisfactory binding agent but layers that incorporated an organic polymer binder were found to be unsuitable. The RF values of chloraniformethan were compared with those of the main co-extractive bands obtained from barley samples, which were found to require the most exacting clean-up of the crops tested. The values obtained with a number of solvent systems are shown in Table I, the best compromise between good separation and convenient running conditions being given by a 1 + 1 mixture of 2,2,4-trimethylpentane and butan-2-one. The RF values of potentially interfering pesticides were then measured for this system. Those compounds which were not readily detected on the fluorescent thin-layer chromatographic plates were rendered visible by spraying with either silver nitrate or Dragendorff's reagent.Samples were applied to commercial 20 x 20 cm thin-layer chromatographic plates, which contained an inorganic binder and inorganic fluorescent (254 nm) additive, by using a commercial streak applicator. No application problems were experienced provided that the sample solution was completely dry and the application was carried out slowly. Control spots of a concentrated chloraniformethan solution were applied at either side of the streak so as to allow the band of interest to be located (by observation of the spots under ultra- violet light) after running the plate. The band was removed simply by scoring around it and then scraping the silica from the plate.It was found to be important to use acetone rather than methanol for washing the sample from this silica gel. The latter solvent is widely recommended for this purpose but caused irreproducible results, apparently as a result of interference by dissolved silica gel during gas chromatography. HOODLESS AND SARGENT: FUNGICIDE RESIDUES. PART v Method Reagents Analytical-reagent grade materials should be used unless otherwise indicated. Acetone, redistilled. Dichloromethane, redistilled. Hexane. Methanol, redistilled. Sodium chloride soldion, saturated. Sodium sulphate, anhydrous, granular. Mobile phase. Add 1 volume of 2,2,4-trimethylpentane to 1 volume of butan-2-one. Chloraniformethan. Technical grade material (about 95% pure) was purified by recrystal- lisation twice from benzene (m.p.132-133 "C, literature value' 134-135 "C) and the product used to prepare a standard 1 mg ml-l stock solution in acetone. Working standards and solutions for fortification of samples were prepared from this solution by further dilution with acetone as required. Redistil laboratory-reagent grade hexane from sodium hydroxide.&larch, 1976 Apparatus HOODLESS AND SARGENT: FUNGICIDE RESIDUES. PART v 163 Grinder. A domestic coffee grinder is suitable. Homogeniser or Son-hlet extraction apparatus. Rotary evaporator. Thin-layer plates. A 1000-pm thick layer of silica gel GF with fluorescent indicator on Remove a 1-cm strip of silica gel from each side before Thin-layer chromatographic applicator (Burkard) with 1-ml syringe (Agla) . Glass tanks for thin-Layer chromatography.The tanks were lined with Whatman No. 1 filter-paper along their longer sides and at their base. Efficient sealing of the lids was en- sured without the use of grease by using spring clamps and a PTFE gasket. Gas chromatographs. Two Pye 104 instruments fitted with 63Ni electron-capture detectors were used isothermally. One detector was operated in the pulsed mode a t a fixed frequency using the standard Pye 104 supply unit (pulse interval set to 150ps) and amplifier. The other detector was operated in the pulse mode at constant current using a combined supply - amplifier unit of the type supplied with Pye GCV gas chromatographs. Both detectors were used at a temperature of 250 "C without a flow of purge gas. The stationary phase was 5% neopentyl glycol succinate on Gas-Chrom Q (supplied by Phase Separations Ltd.) packed into a silanised glass column, 0.9 m x 4 mm i d .The column was operated at 180 "C with a nitrogen carrier gas flow-rate of 40 ml min-l. The temperature of the injection port was also maintained at 180 "C. 20 x 20 cm glass plates (Anachem). use. Procedure Fortijcation solution to the ground or chopped sample. sample was sealed and stored overnight at -20 "C before analysis as described below. ExtractioN For the Soxhlet extraction, place 20 g of ground or chopped sample in the paper thimble and extract it for 4 h with 200 ml of methanol and a rate of heating such that the solvent cycles about twenty-five times per hour. Alternatively, samples can be homogenised three times with methanol in a 150-ml vortex beaker, the mixture being filtered on a Buchner funnel fitted with a glass sinter and washed with methanol after each operation. A total of 200 ml of methanol is used.Analysis Dilute the methanol extract with distilled water (40ml for grain samples and 20ml for cucumber samples) and add 10 ml of saturated sodium chloride solution. Extract twice with 50-ml portions of hexane and discard the extracts. Add a further 100 ml of water and extract with two 50-ml portions of dichloromethane. (It is essential that these extracts are completely dried before proceeding further.) Dry the extracts by shaking them with anhydrous sodium sulphate and then, in order to ensure that they are completely dry, pass them through a further 20 g of sodium sulphate in a 20 mm diameter glass column.Com- bine the extracts and any washings in a 250-ml round-bottomed flask. Concentrate the solution to a volume of about 1 ml using the rotary evaporator (under reduced pressure with the water-bath at 40-50 "C). Carefully wash the extract out of the flask with dichloromethane, making the solution up to volume in a 2-ml calibrated flask. This step can be carried out successfully only if the dichloromethane solution is completely dry. Fill the syringe from the applicator using about 1 ml of the concentrated solution of the extract. Apply 0.50 ml of this solution to a thin-layer chromatographic plate in the form of a 10-cm streak about 3 cm from the bottom of the plate using twenty-five applications of 2Opl each. Ensure that a narrow band of extract is obtained by drying carefully with a stream of cold air between each application.Apply a 5-p1 spot of standard chloranifor- methan solution (a 1 mg ml-1 solution in acetone) either side of the streak of extract. Score a line across the plate 10 cm ahead of the front of the extract band. Run the plate in the development solvent immediately, ensuring that the solvent is allowed to run up to the scored line. Samples were fortified for use in recovery experiments by the addition of a standard acetone After allowing the acetone to evaporate, the Keep the tank in the dark.164 HOODLESS AND SARGENT: FUNGICIDE RESIDUES. PART v Analyst, VoZ. 10f After development, dry the plate in a current of cold air, again in the dark if possible.Very briefly examine the plate under ultraviolet light and mark the two chloraniformethan spots. Remove a 10 x l-cm band of silica gel from the plate between the spots (it may be more satisfactory to remove a 1.5-cm band if the original streak has spread to any extent). Pack the silica gel into a small glass column plugged with silanised glass-wool and dry it further by passing a flow of cold air through the column. Elute the column with acetone, collecting the eluate in a 10-ml calibrated flask, and make the volume up to the mark with acetone. Inject 5 4 of this solution into the gas chromatograph and compare the peak height with those obtained for 5-p1 injections of standard solutions. When using the con- ventional (fixed frequency) electron-capture detector, ensure that the peak heights of the sample and standard solutions are directly comparable.Results Chloraniformethan was found to give excellent sensitivity on both electron-capture de- tector system used. With a signal to noise ratio of 3: 1 the detection limits were 0.05 ng with constant-current operation and 0.15 ng with fixed pulse frequency operation. This difference is not significant and may be partly explained by minor differences that exist between the two gas chromatographs and their columns. Linearity of calibrations was observed from the detection limit up to about 1 ng with the fixed pulse frequency detector and to greater than 2.5ng with the constant-current detector. The detection limits for chloraniformethan in sample extracts are slightly poorer and vary to some extent with in- dividual samples.However, detection limits (as defined above or, when co-extractive peaks coincide, as four times the height of any interfering peak) in the samples investigated are estimated to be 0.1 mg k g l in barley, 0.05mg kg-l in wheat and 0.05 mg k g l in cucumber. The RF values of chloraniformethan for eighteen different thin-layer chromatographic solvent systems are shown in Table I. This table also shows the RF values for three co- TABLE I R p VALUES OF CHLORANIFORMETHAN AND BARLEY CO-EXTRACTIVES ON SILICA GEL G F PREPARATIVE THIN-LAYER CHROMATOGRAPHIC PLATES RF value Chlorani- ,-- Solvent formethan (i) 0.21 2,2.4-Trimethylpentane - tetrahydrofuran (1 + 1) . . . . 0.41 0.40 2,2,4-Trimethylpentane - acetone - diethyl ether (5 + 3 + 2) 0.29 2,2,4-Trimethylpentane - butan-2-one (1 + 1) .. . . 0.50 0.34 2,2,4-Trimethylpentane - ethanol (1 + 1) . . .. . . 0.64 0.72 2,2,4-Trimethylpentane - dichloromethane - ethyl acetate (3 + 4 + 3) .. .. .. . . 0.30 0.30 Methanol - diethyi kther'(i + 99j . . .. .. . . 0.39 0.35 Acetone - diethyl ether (1 + 99) . . a . .. . . 0.35 0.68 Ethyl acetate - diethyl ether (7 + 3) . . .. .. . . 0.50 0.76 Ethyl acetate - diethyl ether (7 + 13) .. .. . . 0.68 0.87 Butan-2-one - diethyl ether (1 + 2) . . .. .. . . 0.70 0.58 Ethyl acetate - diethyl ether (1 + 1) . . .. .. . . 0.67 0.79 Ethyl acetate - dichloromethane (3 + 7) . . .. . . 0.68 0.46 Acetone - hexane (1 + 1) . . .. .. .. . . 0.43 0.64 Chloroform .. .. .. .. .. . . . . 0.11 0.11 2,2,4-Trimethylpentane - acetone - diethyl ether (3 + 1 + 1) 0.19 0.31 Butan-2-one - benzene (1 + 3) , ... .. .. . . 0.20 0.20 Ethyl acetate . . .. .. .. .. .. . . 0.92 0.96 Propan-2-01 . . .. .. .. .. .. . . 0.71 0.69 Barley (ii) 0.14 0.11 0.17 0.16 0.40 0.17 0.18 0.33 0.42 0.61 0.40 0.09 0.61 0.31 0.40 0.08 0.21 0.06 (iii) 0.05 0.09 0.11 0.20 - 0.08 0.09 0.68 0.18 0.26 0.17 0.16 0.21 0.21 0.13 0.03 - - extractive bands [(i)-(iii)] obtained from barley. In each system these bands are the three most interfering bands present and do not necessarily represent the same co-extractive in each instance. Barley was used, as our main aim was to develop a method for this crop, but the solvent system selected on the basis of these data was also suitable for wheat and cucumber samples. The mixture 2,2,4-trimethylpentane - butan-2-one (1 + 1) was chosen as the solvent because as well as giving good separation of chloraniformethan from co-Alarch, 1976 HOODLESS AND SARGENT: FUNGICIDE RESIDUES.PART v 165 extractives, it gave clear, reproducible chromatograms, was easy to use and gave a reasonable development time (about 30 min). Fig. 1 shows the chromatograms obtained with barley, wheat and cucumber samples taken through the standard procedure described above. Barley Wheat Cucumber Fig. 1. Thin-layer chromatograms obtained with barley, wheat and cucumber samples taken RF values are measured from the front of the 2 mm Broken lines indicate un- through the procedure described in the text. wide sample streak. sharp edges of bands. Chloraniformethan gives an lip value of 0.50.a b C Bands visible by white Bands visible by absorption a t light 254 nm a t 366 nm Bands visible as fluorescence 1 Very faint yellow 1 Very faint 1 Bright grey 2 Faint yellow 2 Faint 2 Bright blue - grey 3 Light yellow 3 Light 3 Light blue 4 Dark yellow 4 Dark 4 Moderately bright blue 5 Light brown 5 Very dark 5 Bright blue 6 Dark brown (6) Yellow coloration 6 Very faint pink 7 Very dark brown (7) General background coloration The RF values for some pesticides that may be used under similar circumstances to those which require the use of chloraniformethan and thus represent a possible interference are shown in Table 11. Organochlorine pesticides (DDT and BHC) were not included as they are removed by the preliminary wash with hexane.It can be seen from Table I1 that only TABLE I1 RF VALUES O F POTENTIALLY INTERFERING PESTICIDES FOR STANDARD THIN-LAYER CHROMATOGRAPHIC CLEAN-UP SYSTEM Pesticide R g value Pesticide RP value Chloraniformethan . . .. . . 0.60 2,3,6-TBA . . .. . I . . 0.00 MCPA .. .. .. .. . . 0.00 Mecoprop . . .. .. . . 0.01 2,4-D . . .. .. .. . . 0.01 Oxydemeton-methyl . . .. . . 0.01 Dichlorprop . . .. .. . . 0.02 Dicamba .. . . .. . . 0.02 2,4-DB . . .. .. .. . . 0.05 Ioxynil . . .. .. .. . . 0.07 Bromoxynil .. .. .. . . 0.09 Ethirimol . . . . .. . . 0.16 Dinoseb . . .. . . . . 0.20 Dimethoate . . .. .. . . 0.21 Triforine . . .. .. . . 0.34 Demeton-S-methyl . . .. . . 0.36 Formothion . . .. .. . . 0.61 Carboxin . . . . . . . . 0.52 Linuron . . .. .. . . 0.64 Fenitrothion . . ... . . . 0.60 Barban .. .. .. . . 0.62 Thiometon . . .. .. . . 0.66 Trithion . . .. . . . . 0.70 . .0.73 + 0.65 Tridemorph . . .. . . three of the compounds included are likely to be removed from the thin-layer chromato- graphic plate with chloraniformethan, namely, formothion, carboxin and linuron. These compounds were found to be well separated from chloraniformethan by the gas-chromato- graphic system : linuron had a much shorter retention time, formothion a far longer retention time and carboxin gave satisfactory separation (about 12 min compared with 8.3 min for chloraniformethan) but in any event the response was more than fifty times less than that for chloraniformethan.166 HOODLESS AND SARGENT The recoveries obtained for fortified samples of barley, wheat and cucumber are shown in Table 111. TABLE I11 Sample Barley RECOVERY O F CHLORANIFORMETHAN FROM FORTIFIED SAMPLES Chloranif or methan Extraction method added/mg kg-l Chloraniformethan recovered, yo Soxhlet Macerated Soxhlet - - W e a t Soxhlet Cucumber Macerated - I Soxhlet 6 6 2 1 0.6 6 0.6 5 0.6 0.6 91, 90, 90 76, 70, 72, 92, 87, 110, 82, 88 85, 85, 92, 91 76, 70, 86, 74, 76, 90, 83, 82 92, 90, 83, 90, 93, 96, 93 86, 78, 85, 79 65, 67, 67, 71 73, 83, 72, 77 79, 70 66, 76 The authors thank the Government Chemist for permission to publish this paper. 1. 2. 3. 4. 5. 6. 7. References German Patent 1 643 604; British Patent 1 123 860, 1968. Martin, T. J., Pjianzenschutz-Nachrichten Buyer, 1971, 24, 196. Ministry of Agriculture, Fisheries and Food, “Recommendations for S?fe Use in the United Kingdom Recommendation Sheet No. Ministry of Agriculture, Fisheries and Food, “1975 List of Approved Products and Their Uses for Piglionica, V., and Salvatore, F., Infme FitofiatoE, 1973, 23, 17; Chem. Abstr., 1974, 81, 86626r. Vogeler, K., Pflanzenschutz-Nachrichten Buyer, 1969, 22, 289. “Pesticide Manual,” Fourth Edition, British Crop Protection Council, Droitwich, 1974, p. 91. of Chemical Compounds Used in Agriculture and Food Storage, 982, 1973. Farmers and Growers,” H.M. Stationery Office, London, 1976. Received October 17th, 1976 Accepted November 1 lth, 1976

ISSN:0003-2654    

DOI:10.1039/AN9760100161

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

Analyst, March, 1976, Vol. 101, pp. 167-173 167 The Determination of C h I o r hyd roxyq u i no1 i ne in Medicated Pig Feeds Part 11." Ultraviolet Spectrophotometric Batching Assay and Gas-chromatographic Assay for Mono- and Dichloro Components T. Cowen and W. F. Heyes Squibb International Development Laboratory, Moreton, Wzrral, Merseyside Two procedures have been developed for determining chlorhydroxyquinoline (halquinol) in pig feed medicated at a level of 120p.p.m. The ultraviolet spectrophotometric procedure can be used to determine halquinol and the gas - liquid chromatographic procedure to determine specifically the 5,7- dichloro- and the combined 5- and 7-chloroquinolin-8-01 components. Halquinol was found to react with copper during the initial extraction with chloroform, thus preventing formation of the silyl ether prior to gas - liquid chromatography.Partitioning the chloroform extract with dilute mineral acid so as to cause dissociation of the chelate and adding EDTA before back- extraction into dichloromethane overcame this problem. Halquinol (chlorhydroxyquinoline) , I, a mixture of chlorinated quinolin-8-01s that has anti- bacterial activity, is added to feeds in order to promote growth and control scours in growing pigs. The mixture contains three structurally related components as shown below. Y H CI 23-40 CI H Not more than 3 I (Halquinol) The spectrofluorimetric determination of halquinol in medicated pig feeds was described in an earlier paper.l This procedure was developed specifically for application to feeds contain- ing 600 p.p.m.of halquinol; when it was applied to feeds containing 120 p.p.m. of halquinol, the high fluorescence values for blank feeds led to interferences of the order of 30%. In order to overcome this interference we sought to develop an alternative extraction procedure. The most convenient way to separate halquinol from co-extracted material proved to be by partitioning the original chloroform extract with dilute mineral acid, thus causing the hal- quinol to be extracted into the aqueous layer in its protonated form. The latter extract was sufficiently free from interfering substances to permit ultraviolet spectrophotometric assay, whereas measurement of fluorescence required chelation of the halquinol with magnesium, a procedure that could not be carried out directly on the acid extract.Consequently, ultra- violet spectrophotometry, rather than spectrofluorimetry, was adopted as a batching assay procedure. A method was also required for determining quantitatively the individual components of halquinol. Use has been made of several gas - liquid chromatographic procedures for separating substituted quinolinols in order to evaluate the isomeric purity of synthesised material.2-6 Silylation of halquinol leads to a separation of the main components at 176 "C on a column of 5y0 JXR on Gas-Chrom Q. The procedure enabled the monochloroquinolinols to be separated from dichloroquinolinol, but it was not possible to distinguish between the 5- and 7-ChlOrO isomers. As the 7-chloro isomer is present in small amounts (usually 1-3%) * For details of Part I of this series, see reference list, p.173.168 COWEN AND HEYES: THE DETERMINATION OF AnaZyst, VoZ. 101 in halquinol, the determination of the total monochloroquinolinol content was considered to be adequate for our purposes. Experimental A common additive to feeds that is intended to promote the growth and fattening of pigs is copper sulphate, which is usually added at a level equivalent to 200 p.p.m. of copper. Other metals such as zinc, calcium and iron are also added as a mineral supplement. These metals readily form chelates with halquinol in solution. Of the metals present in an animal feed, copper is the most strongly chelated and this chelate is predominantly formed during solvent extraction of the feed. It is therefore essential that the solvent used to extract a feed for assay purposes be that in which both halquinol and its copper chelate are appreciably soluble.Only chloroform meets this requirement, but it also extracts various interfering materials from animal feedstuffs; further extraction is required in order to produce a solution that is free from co-extracted feed substances. Partitioning a chloroform extract of a feed containing halquinol with dilute sulphuric acid caused the halquinol and its copper chelate to be extracted into the aqueous layer as the protonated forms of the chloroquinolinols, leaving the interfering substances in the chloroform layer. Subsequent difficulty due to the formation of emulsions was overcome by evaporating the chloroform and dissolving the residue in hexane before partitioning the organic phase with dilute acid.Unfortunately, it was not possible to extract the feed directly with hexane or with dilute acid because of the insolubility of the halquinol - copper chelate in the former and the slow dissolution of solid halquinol in the latter. The extraction of samples of blank feed spiked with known levels of halquinol, by adding chloroform and shaking the mixtures at room temperature, resulted in an average 80% recovery of active material. In order to obtain satisfactory recoveries (95% or more), it was necessary to reflux the feed with chloroform for 2 h. In developing the gas - liquid chromatographic assay, we aimed to make the initial prepara- tion of the sample as simple as possible; in this context we attempted direct extraction of a feed with chloroform.After silylation, aliquots of the solution were injected into the chroma- tograph, but from the large number of peaks observed it was obvious that some form of clean-up procedure would be required. In addition, some of the halquinol present in the feed was extracted as the copper chelate, in which the 0-H bond of the hydroxyl group of the quinolinol is replaced by an 0-Cu bond. The chelate would not be expected to react with silylating reagents prior to the Chromatography, and an apparent loss of halquinol would result during extraction. In order to overcome these difficulties, we applied the same extraction procedure as that used in the spectrophotometric assay. Protonated halquinol in the aqueous layer was then back-extracted into an organic solvent after adjustment of the pH to 7.EDTA solution was added prior to the pH adjustment so as to prevent any recom- bination of halquinol with the copper ions. After evaporation of the solvent on a rotary evaporator, a silylating reagent was added to the solution before gas - liquid Chromatography. The discovery that the copper chelate dissociated more rapidly in dilute perchloric acid than in dilute sulphuric acid led to the use of perchloric acid for subsequent extractions during the development of the gas - liquid chromatographic assay. Application of this proposed procedure to a blank feed demon- strated the presence of a small amount of co-extracted material, the retention time of which showed it to be completely resolved from the mono- and dichloroquinolinols, and therefore no interference with the assay was expected.Several assays of a medicated feed by gas - liquid chromatography gave low and erratic recoveries of halquinol, the poor reproducibility being traced to the rotary evaporation stage of the extraction procedure. Halquinol is slightly volatile at the temperature used for the evaporation of chloroform. The assay results were improved by adding silylating reagent before evaporating the solvent and by substituting a more volatile solvent (dichloromethane) for the original back-extraction solvent (chloroform), so that rotary evaporation could be carried out at a lower temperature. Although the use of dilute perchloric acid resulted in a more rapid dissociation of the halquinol - copper chelate and was incorporated in the gas - liquid chromatographic assay procedure so as to improve the efficiency of the partitioning, we retained the use of dilute sulphuric acid in the spectrophotometric batching assay mainly for economic reasons.March, 1976 Reagents CHLORHYDROXYQUINOLINE IN MEDICATED PIG FEEDS.PART 11 Spectrophotometric Batching Assay Asbestos fibre. Micro-analytical grade, acid washed. Halquinol. A sample used to medicate the feed, or a suitable reference standard. Chloroform. AnalaR grade. Hexane. Fraction from petroleum (BDH Chemicals Ltd.). Sulphuric acid, 1.0 M . 169 Apparatus All absorbance measurements were made on a Hilger and Watts H700 spectrophotometer. Extraction of Sample Weigh accurately about 10 g of the feed into a 250-ml round-bottomed flask, add 100 ml of chloroform and reflux the mixture for 2 h.Filter it immediately through a No. 4 sintered funnel pre-coated with a 0.5411 bed of asbestos fibre. The sinter is pre-coated by adding the asbestos as a chloroform slurry. Use a further 50 ml of chloroform in order to complete the transfer and to wash the feed residue. Evaporate the filtrate to about 1 ml on a rotary evaporator and then gently remove the remaining chloroform with a stream of nitrogen. Using two consecutive 60-ml volumes of hexane, transfer the residue quantitatively into a 250-ml separating funnel, then extract the halquinol from the hexane phase with five consecutive 95-ml volumes of 1.0 M sulphuric acid. The first two portions of acid should be used to complete the transfer of halquinol from the round-bottomed flask into the separating funnel.Collect the extracts in a 500-ml calibrated flask and dilute to volume with 1.0 M sulphuric acid. Filter an aliquot of the extract through a Whatman No. 42 filter-paper, discarding the first 25 ml of filtrate. Preparation of Standard Weigh accurately about 25 mg of halquinol into a 100-ml calibrated flask. Dissolve the sample in and dilute to volume with 1.0 M sulphuric acid. Pipette 5 ml of this solution into a 500-ml calibrated flask and again dilute to volume with 1.0 M sulphuric acid. Measurement of Absorbance Measure the absorbance of the sample and standard solutions against 1.0 M sulphuric acid in 1-cm silica cells at 258 nm. Repeat the absorbance measurements on the samples alone at 290 nm.Subtraction of the sample absorbance at 290 nm from that at 258 nm corrects for the background absorbance of co-extracted substances. The concentration of halquinol in the sample of medicated feed can then be calculated. Gas-chromatographic Assay for Mono- and Dichloro Components Reagents and Materials Asbestos fibre, chloroform and hexane as before. Carbon disulphide. AnalaR grade. Dichloromethane. Analytical-reagent grade. 5-ChZoroquinolin-8-ol. A sample of material that was shown to contain no dichloro- 5,7-Dichloroq~inolin-8-ol. A sample of material that was shown to contain no mono- Perchloric acid, 1.0 M. Sodium hydroxide solution, 10.0 M. E D T A solution, 5% m/V. Bufer solution, p H 7. Dissolve 27.2 g of potassium dihydrogen orthophosphate in about 700ml of distilled water.Adjust the solution to pH 7.0 with sodium hydroxide solution, then dilute to 1 1 with distilled water. Internal standard. Dissolve 25 & 1 mg of eicosane (analytical-reagent grade, BDH Chemicals Ltd.) in dichloromethane and dilute the solution to 50 ml with dichloromethane. quinolinol. chloroquinolinols .170 COWEN AND HEYES: THE DETERMINATION OF Analyst, Vol. 101 Stationary phase. JXR (Applied Science Laboratory Supplies). Gas-Chrom Q, 100-120 mesh. Column packing. Dissolve 0.5 g of JXR in toluene. Add l o g of Gas-Chrom Q to the solution and evaporate off the solvent with a rotary evaporator. The final traces of solvent can be removed by drying the packing in an open dish at 60 "C under vacuum. Silylating reagent [NO-bis(trimethylsilyl)acetamide, BSA] Laboratory-reagent grade (BDH Chemicals Ltd.).Apparatus All of the experimental work described was carried out with a Pye, Series 104, gas chromato- graph, equipped with a flame-ionisation detector, and single-column operation with injection heater and on-column injection. Column. A glass column, 5 foot long and of 4 rnm i.d., was packed with the prepared column packing of 5% JXR on 100-120-mesh Gas-Chrom Q. Conditioning was then carried out according to the schedule described by Vandenheuvel and Court.g The following operating conditions were used. The measured gas flow-rates were : carrier gas, oxygen-free nitrogen, 80 ml min-l; hydrogen, 80 ml min-l; and air, 600 ml min-l. An oven temperature of 178-180 "C, together with an injection heater temperature of about 200 "C (setting 5), produced satisfactory chromatograms.Preparation of Standard Weigh accurately on a microbalance about 4mg of 5-chloroquinolin-8-o1 and 7 mg of 5,7-dichloroquinolin-8-01 into the same 50-ml calibrated flask. Dissolve the samples in chloroform and dilute the solution to volume with chloroform. Pipette 5 ml of this solution into a 100-ml separating funnel containing 50 ml of hexane. Continue as described below under Extraction Procedure. Preparation of Sample Weigh accurately about log of feed into a 250-ml round-bottomed flask, add 40ml of chloroform and reflux the mixture for 2 h. Cool and filter the sample through a No. 4 sintered funnel, pre-coated with a 0.5-in bed of asbestos fibre (the sinter is pre-coated by adding the asbestos as a chloroform slurry).Use a further 50 ml of chloroform to complete the transfer and to wash the feed residue. Evaporate the filtrate to about 1 ml on a rotary evaporator and transfer the residue quantitatively into a 100-ml separating funnel, using four 10-ml portions of hexane. Finally, rinse the round-bottomed flask with two 4-ml portions of chloroform and add these to the separating funnel. Continue as described below under Extraction Procedure. Extraction Procedure Extract the halquinol from the hexane phase with four consecutive 15-ml volumes of 1.0 M perchloric acid and collect the extracts in a 250-ml beaker. Add 10 ml of 5% EDTA solution to the acid in the beaker, then adjust the pH to 7 (with a pH meter) with 10.0 M sodium hydroxide solution.Add 25 ml of pH 7 buffer and transfer the contents of the beaker quantitatively into a 250-ml separating funnel. Wash the beaker with two 10-ml portions of distilled water and two 5-ml portions of dichloromethane, trans- ferring each wash into the 250-ml separating funnel. Shake the funnel well for 2 min, allow the layers to separate, then run the lower layer into a 50-ml calibrated flask. Extract the halquinol with three further 10-ml portions of dichloromethane, collecting the extracts quantitatively in the flask. Add, by pipette, 2 ml of internal standard solution to the flask, then dilute to volume with dichloromethane. After mixing the flask contents, pipette 25ml of this solution into a 50-ml pear-shaped flask, add 0.25 ml of silylating reagent and evaporate the solution to dryness on a rotary evaporator at room temperature. Add to the flask a further 0.2ml of silylating reagent, followed by 1 ml of carbon disulphide.This solution of the silyl derivative is fairly stable but should not be stored overnight.March, 1976 CHLORHYDROXYQUINOLINE IN MEDICATED PIG FEEDS. PART 11 171 Gas - Liquid Chromatographic Procedure Inject 2.5-p1 aliquots of sample and standard solutions on to the column and, from the resulting traces, determine the peak height ratio of each component to internal standard for each injection. The contents of 5-CNOrO- and 5,7-dichloroquinolin-8-01 in the feed can then be calculated. A typical trace is shown in Fig. 1. 1 2 I Y 3 4 Fig.1. Typical gas - liquid chromatographic trace of halquinol in feed ex- tract: 1, 6-chloroquinolin-8-o1 (Rt = 2 min); 2, 6,7-di- chloroquinolin-8-01 (R, = 3.6 min) ; 3, internal standard (eicosane, R, = 7 min); and 4 and 6, co-extracted matter from feed (R, = 8.6 and 17 min). Discussion and Results Correction for Background Absorbance The ultraviolet spectrophotometric batching assay described above involves absorbance measurements at two wavelengths, namely 258 and 290 nm. This procedure corrects for the interference of co-extracted material, which is typically of the order of 10%. By this means, assay of a blank feed is not required. The ultraviolet absorbance spectrum of a blank feed shows the absorbance to be constant between 253 and 300nm. As the absorbance of the standard solution is virtually zero at 300 nm, an absorbance measurement at this wavelength allows a correction to be made for the contribution by the blank in an extracted sample.Obviously this procedure applies only to the particular feeds used in the development of the assay. It is possible that other manufacturers’ feeds may not yield extracts that have the same characteristics. Effect of Silylation Although the gas - liquid chromatographic procedure described does not enable the in-172 COWEN AND HEYES: THE DETERMINATION OF Analyst, Vol. 101 dividual monochloro components of halquinol to be assayed, the assay of the total mono- chloroquinolinol content was considered to be adequate, for reasons explained earlier. All three components of halquinol can be separated with a column of 10% OV-17 on Gas-Chrom Q at a temperature of 200 "C, but only if halquinol is chromatographed without prior sily- lation.7 Formation of the silyl ether prior to chromatography results in the two monochloro derivatives being eluted at the same time.However, we considered it to be essential to silylate the halquinol at the expense of separating the two monochloro isomers, for reasons that concern the chelating properties of quinolinols. The presence of any metal surface, for example, a syringe needle or parts of the flame-ionisation detector, especially at elevated temperatures, would result in a loss of chlorhydroxyquinoline by chelate formation with the metal surface, thereby introducing further sources of error into the method.In addition, evidence was obtained indicating that unsilylated halquinol is not completely eluted from the column during chromatography. Injection of solvent alone results in the production of small peaks that have the same retention times as the halquinol components, a phenomenon that does not occur when the silyl ether of halquinol is chromatographed. Applicability Attempts to apply the assay procedures to feeds containing 600 p.p.m. of halquinol were unsuccessful because a halquinol - copper chelate precipitated during extraction, as had been expected from earlier work on the solubility of the chelate. Although reduction of the amount of medicated feed used in the assay averted the precipitation of a chelate, it resulted in problems associated with the homogeneity of the feed.No limitations are anticipated with feeds that contain less than 120 p.p.m. of halquinol. The assay procedures are therefore recommended for use only when the level of active substance is not greater than 120 p.p.m. A number of other common medicinal feed additives that may possibly be present have been examined for their effect on the assay procedures described. Nitrovin, arsanilic acid and Eskalin (virginiamycin) at levels of 10, 250 and 10 p.p.m., respectively, do not interfere. Dimetridazole, at a level of 200 p.p.m. does cause interference and should be absent. Validity The validity of the above procedures was ascertained by preparation of samples of feed spiked at a level of 120 g of halquinol per ton of feed. Spiking was accomplished by adding aliquots of a solution of halquinol in chloroform to 10 g of unmedicated feed (Messrs.Tyrell, Byford & Pallet Ltd., Norfolk), the chloroform being subsequently removed by rotary eva- poration. Halquinol was added in this manner to achieve maximum adsorption of active substance by the feed. Table I shows the recovery of halquinol from the feed by use of the procedures described above. In all instances, the recovery values were considered to be acceptable for an assay of animal feed containing a very low level of active substance. TABLE I RECOVERY OF HALQUINOL FROM SPIKED FEEDS (120 g t0n-l) 7 Added, p.p.m. photometric assay 126 125 123 124 126 Ultraviolet spectro- i i o 110 110 110 102 102 Gas - liquid chromatographic assay Halquinol Recovered, p.p.m.- 118 118 114 117 118 105 105 107 107 96 99 5-Chloro component 5,7-Dichloro component Y A Y m Recovery, Added, Recovered, Recovery, Added, Recovered, Recovery, % % p.p.m. p.p.m. % p.p.m. p.p.m. 94 94 93 94 94 95 95 97 97 94 97 42 41 98 78 73 94 42 42 100 78 72 92 43 45 105 80 77 96 43 46 107 80 75 94 43 45 105 80 73 91 43 46 108 80 76 9sMarch, 1976 CHLORHYDROXYQUINOLINE IN MEDICATED PIG FEEDS. PART 11 173 Application of the procedures to manufactured batches of medicated feeds stored for periods as long as 6 months at temperatures between ambient and 40 "C showed good agree- ment between the results of the ultraviolet spectrophotometric assay and gas - liquid chro- matographic determination of the individual components. In Table I1 the results obtained with four batches of medicated feeds are compared, the two procedures being carried out independently on separate extracts. TABLE II COMPARISON OF ULTRAVIOLET SPECTROPHOTOMETRIC AND GAS - LIQUID CHROMATOGRAPHIC ASSAY RESULTS Ultraviolet r spectrophoto- metric assay Sample total, p.p.m. 1 110 2 105 3 112 4 94 Gas - liquid chromatographic assay A b Monochloro Dichloro components, components, p.p.m. p.p.m. Total, p.p.m. 30 85 115 29 78 107 39 77 116 34 58 92 1. 2. 3. 4. 5. 6. 7. References Fairbrother, J. E., and Heyes, W. F., AnaZyst, 1973, 98, 797. Gruber, M. P., Klein, R. W., Foxx, M. E., and Campisi, J., J . Pharm. Sci., 1972, 61, 1147. Ohlson, B., Svensk Farm. Tidskr., 1973, 77, 631. Gershon, H., McNeil, M. W., and Grefig, A. T., J . Org. Chem., 1969, 34, 3268. Hortmann, V., and Herrmann, W., Pharm. Ind., B e d , 1974, 36, 202. Vandenheuvel, F. A., and Court, S. A., J . Chrumat., 1968, 38, 439. Simpson, K., personal communication. NOTE-Reference 1 is to Part I of this series. Received Sefitember 16th, 1976 Accepted October 20th, 1976

ISSN:0003-2654    

DOI:10.1039/AN9760100167

出版商:RSC    

年代:1976

数据来源: RSC