摘要:

974 Analyst, October, 1980, Vol. 105, **. 974-980 Determination of Cyanide in Animal Feeding Stuffs J. R. Harris, G. H. J. Merson, M. J. Hardy* and D. J. Curtis Department of Industry, Laboratory of the Government Chemist, Cornwall House, Stamford Street, London, SE1 9NQ A method for the determination of cyanide in feeding stuffs has been developed. Naturally occurring cyano-substituted glycosides are subjected to enzymatic hydrolysis, the liberated cyanide is isolated by aeration and determined either by a spectrophotometric method or by gas chromatography. Recoveries of cyanide added to feeding stuffs at concentrations of 10 and 20 mg kg-' were approximately 98%. The method is sensitive to as little as 1 mg bg-1 of cyanide. Keywords; Cyanide determination; animal feeding stuffs; enzymatic hydvolysis; spectrofihotometry; gas chromatography Cyanide in trace amounts is found in a large number of plants, mainly in the form of cyano- substituted glycosides.Relatively high concentrations are found in certain grasses, pulses, roots and fruit kernels. Glycosides that have been positively identified include amygdalin in fruit kernels, especially bitter almonds; dhurrin in sorghum and other grasses; and linamarin in pulses, linseed and cassava. The structures and reactions by which these glycosides release free cyanide have been described by Montgomery1 and Conm2 Of the plant products mentioned above, sorghum, linseed (after extraction of linseed oil) and cassava are important ingredients in animal feeding stuffs but their use is restricted by the presence of the cyano- substituted glycosides.The EEC Directive3 on the control of undesirable substances in feeding stuffs prescribes maximum concentrations of hydrogen cyanide for both straight and complete feeding stuffs, ranging from 350 mg k g l (as hydrogen cyanide )for linseed cake down to 10 mg kg-l for complete feeding stuffs for chicks. The EEC method4 prescribed for the determination of cyanide involves enzymatic hydro- lysis, steam distillation and silver nitrate (Volhard) titration. The method is not specific for hydrogen cyanide and its lack of sensitivity is such that for concentrations of 10 mg k g l , only 0.2 ml of 1 N silver nitrate solution is consumed. This paper describes a procedure that is free from interferences and its sensitivity permits as little as 1 mg kg-I to be determined.As Cooke5 pointed out, most methods for the determination of cyanide have three stages: (i) hydrolysis of the cyano-substituted glycoside; (ii) isolation of the cyanide, for example by steam distillation or aeration; (iii) determination of the cyanide. This author states that most of the difficulties arise in stages (i) and (ii), as there are good techniques for cyanide determination; we would agree with Cooke although in our experience stage (ii), the isolation of the cyanide, is the most troublesome. Although methods for the determination of cyanide in plant materials have been published by C ~ o k e , ~ Wood,6 Blaedel et aL7 and Winkler,* none of these is directly applicable to compound animal feeding stuffs.In the determination stage Barkg considers that, for trace amounts of cyanide, the most suitable method is the spectro- photometric procedure based on the Konig synthesis of a pyridint. dyestuff by the reaction between cyanogen bromide and a suitable aromatic amine. In a further paper, Bark and HigsonlO recommended 9-phenylenediamine as the most suitable coupling agent ; this com- pound is specified in the method for the determination of cyanide in water,ll and has been adopted in the proposed method. More recently, gas-chromatographic m e t h ~ d s l ~ - ' ~ for trace amounts of cyanide have been described. In these methods the cyanide ion is reacted with bromine to produce cyanogen bromide, which, after separation on the gas chromatographic column, is determined by the use of an electron-capture detector.'This procedure is included in the proposed method as an alternative to the spectrophotometric prlocedure. * Present address: Beecham Pharmaceuticals Research Division, Great Burgh, Epsom, Surrey. Crown Copyright.975 HARRIS, MERSON, HARDY AND CURTIS Experimental Reagents Orthophosphoric acid, 10% VjV and 0.1 M. Hydrochloric acid, d = 1.18 g ml-l and 0.5 M. Sodium hydroxide solutions, approximately 0.5 and 1 M. Phosphate buffer solution, pH 7.0. in water and dilute to 1 1 with water. hydroxide solution. Dissolve 27.22 g of potassium dihydrogen orthophosphate Adjust the pH of the solution to 7.0 with 5 M sodium Bromine water. Saturated solution. Arsenious acid solution. Dissolve 2 g of arsenic(II1) oxide in 100 ml of water by boiling under reflux.Pyridine solution. Mix 150 ml of pyridine with 100 ml of water and add 25 ml of hydro- chloric acid (d = 1.18 g ml-l). p-Phenylenedaamine dihydrochloride solution. Dissolve 0.17 g of p-phenylenediamine hydrochloride (or 0.1 g of 9-phenylenediamine) in 50 ml of 0.5 M hydrochloric acid. p-Phenylenediamine - pyridine reagent. For each determination mix 15 ml of pyridine solution with 5 ml of p-phenylenediamine dihydrochloride solution immediately before the test. Diisopropyl ether. Phenol, 57; mjV aqueous solution. Potassium cyanide stock solution. Dissolve 1.563 g of potassium cyanide in water, add 25 ml of approximately 1 M sodium hydroxide solution and dilute to 250 ml. Standardise the solution against 0.1 M silver nitrate solution (1.0 ml of 0.1 M silver nitrate solution = 2.5 mg To 10.0 ml of stock solution add 50 ml of approximately 1 M sodium hydroxide solution and dilute to 500 ml (1.0 ml = 50 pg of CN-).To 10.0 ml of intermediate stock solution add 50 ml of approximately 1 M sodium hydroxide solution and dilute to 500 ml. Prepare the inter- mediate and working solutions freshly as required (1.0 ml = 1.0 pg CN-). Chop very finely or grind (preferably in a coffee grinder) 10 blanched sweet almonds and suspend in 100 ml of water. of CN-). Potassiuwz cyanide intermediate stock solution. Potassium cyanide aorking solution. Almond suspension. Shake the mixture thoroughly before use. Apparatus Aeration apparatus. The apparatus consists of a train of four flasks, each fitted with a Drechsel-bottle head.The reaction flask is of 500-ml capacity, round bottomed with a long neck. Preceding the reaction flask is a conical flask (250 or 500 ml) containing 0.5 M sodium hydroxide solution (to remove trace amounts of sulphur dioxide from the incoming air). Following the reaction vessel are two conical flasks (250 ml), each containing 50 mi of 0.5 M sodium hydroxide solution for absorption of the liberated hydrogen cyanide. (A Cecil CE595 double-beam ultraviolet spectrophotometer was used.) (A Pye Unicam GCV fitted with a nickel-63 electron-capture detector was used.) Operat- ing temperatures: column, 100 "C; injector, 125 "C; detector, 150 "C. The flask is immersed in a water-bath a t 37-40 "C. Spectrophotometer. Gas chromatograph. Column. With 10-mm cells, operated a t 515 nm.Fitted with an electron-capture detector. Silanised glass, 1 m x 4 mm i.d., containing Porapak Q (80-100 mesh). Procedure Extraction Weigh, to the nearest 0.005 g, approximately 20 g of the finely divided and mixed sample (previously ground to pass a 1-mm sieve) and transfer it into a 500-ml conical flask. Add by pipette 200 ml of 0.1 M orthophosphoric acid, stopper the flask and shake for 1 h. Allow the contents of the flask to settle and decant the supernatant liquid into a 250-ml centrifuge bottle and spin a t 2500 rev min-1 for 5 min. Transfer the supernatant liquid into a clean dry flask.976 HARRIS et al. : DETERMINATION OF Analyst, Vol. 105 Enzymatic hydrolysis Place approximately 250 ml of the phosphate buffer solution into the enzymolysis flask and add 10 ml of sweet almond suspension and two drops of antifoam.Introduce by pipette 50 ml of the sample extract prepared as described in the previouis section. Fit the bubbler system on to the enzymolysis flask and aerate the contents with an air flow of approximately 1.5 1 min-1 for 18 h, maintaining the temperature of the reaction mixture a t 3740 “C by means of a water-bath. Collect the liberated hydrogen cyanide in two 250-ml conical flasks arranged in series and each containing 50 ml of approximately 0.5 M sodium hydroxide solution. Quantitatively combine the solutions in a 200-ml calibrated flask, dilute to the mark with water and mix. Blank of the sample extract and following the procedure described under Enzymatic hydrolysis.Determination Spectrophotometric method Into a 50-ml calibrated flask transfer an aliquot portion of the sample solution obtained from the enzymatic hydrolysis, not exceeding 20 ml and expected to contain not more than 20 pg of cyanide (as CN-). In a second 50-ml calibrated flask place an identical volume of the hydrolysis blank solution. To each flask add 0.5 ml of hydrochloric acid (d = 1.l8gm1k1), mix and then immediately add 0.5 ml of bromine water. Stopper the flasks to prevent losses of cyanogen bromide, mix and allow to stand for 2 min. Add to each flask 0.5 ml of arsenious acid, mix thoroughly to remove excess of bromine, then add 20.0 rnl of p-phenylenediamine - pyridine reagent, dilute to the mark with water, mix and allow to stand for 40 min. Without further delay measure the absorbance of the solutions at 515 nm in 10-mm cells against water as reference.Subtract the absorbance of the hydrolysis blank from that of the sample and determine the amount of cyanide in the sample solution by reference to the calibration graph. Transfer by pipette into a series of 50-ml calibrated flasks 5, 10, 15 and 20 ml of the cyanide working solution and dilute as necessary to 20 ml with water. In addition include one flask containing 20 ml of water without cyanide as the reagent blank. Proceed as described above from “To each flask add 0.5 ml of hydrochloric acid . . .” Measure the absorbance of each solution after 40 min a t 515 nm in 10-mm cells against water as reference. Subtract the absorbance of the reagent blank from those of the cyanide standards and plot the calibration graph using the net absorbance values on the ordinate atnd the corresponding masses of cyanide (as micrograms of CN-) on the abscissa.Gas-chromatographic method Into a 100-ml separating funnel transfer an aliquot portion of the sample solution obtained from the enzymatic hydrolysis, not exceeding 20 ml and expected to contain not more than 8 pg of cyanide (as CN-)*. Into a second separating funnel place an identical volume of the hydrolysis blank solution. Make up the volumes to 20 ml if necessary. Add 5 ml of 10% VjV orthophosphoric acid solution and 0.5 ml of bromine water. Shake each funnel and allow to stand for 15 min, then add 0.2 ml of 5% m/V aqueous phenlol solution and gently shake. Add 20.0 ml of diisopropyl ether to each funnel, stopper firmly and shake vigorously for 2 min.Allow the phases to separate, then discard the lower aqueous phase and transfer the diisopropyl ether layer into a vial fitted with a septum cap. Inject 1.0 pl of each solution on to the column and measure the heights of the cyanogen bromide peaks obtained. Subtract the peak height of the cyanogen bromide in the hydrolysis blank solution (if any) from that of the sample and determine the amount of cyanide in the solution by reference to the calibra- tion graph. Calibration graph. Transfer by pipette into a series of 100-ml separating funnels 2, 4, 6, 8 and 10 ml of cyanide working solution, dilute as necessary to 20 ml with water. In addition * The amount of cyanide in the solution injected into the gas chromatograph must be within the linear range of the detector.In some instances it may be necessary to reduce both the recommended maximum content in the sample solution and the amounts prescribed for the calibration graph in order to meet this requirement. Carry out a blank enzymatic hydrolysis using 50 ml of 0.1 M orthophosphoric acid in place Calibration graph.October, 1980 CYANIDE IN ANIMAL FEEDING STUFFS 977 include one separating funnel containing 20 ml of water without cyanide as the reagent blank. Proceed as described above from “Add 5 ml of 10% VjV orthophosphoric acid. . .” Measure the heights of the cyanogen bromide peaks and, after correcting for the reagent blank, plot the calibration graph of corrected peak height against the corresponding mass of cyanide (as micrograms of CN-).Calculation The same calculation is applicable to both procedures. The cyanide content of the feed in milligrams per kilogram is given by 800 x A M x V where A = mass of cyanide (as micrograms of CN-) present in the aliquot portion of the sample extract, M = mass of test portion (grams) and V = volume of the aliquot portion taken for the determination (millilitres) . Results and Discussion Recovery of Cyanide from Cyano-substituted Glycosides The efficiency of the proposed method was assessed by adding to the orthophosphoric acid used in the extraction stage known amounts of amygdalin (Aldrich Chemical Co. Ltd; cyanide content 5.69% m/m as CN-) and linamarin (Calbiochem, Bishops Stortford, Hertfordshire; cyanide content 10.52% mlrn as CN-) and following the procedure described above.The results are given in Table I and show that near-quantitative yields of cyanide were obtained. TABLE I RECOVERY OF CYANIDE FROM AMYGDALIN AND LINAMARIN IN THE ABSENCE OF FEED Spectrophotometric method GC method 1 CK- added r------- - r---L--- Glycoside PLg P8 % Pg % as substratel CN- found/ Recovery, CN- found/ Recovery, Amygdalin. . 200 200 197 201 400 405 389 397 Linamarin . . 200 194 197 199 191 191 198 100.0 98.5 100.5 101.3 97.3 99.3 97.0 98.5 99.5 95.5 95.5 99.0 197 98.5 199 99.5 196 98.0 - - - - 196 98.0 201 100.5 197 98.5 - - Having established the efficiencv and reliability of the method when applied to amygdalin and linamarin, it was then applied to a series of compound feeding stuffs fortified with these two glycosides.The results of these studies are shown in Table 11, from which the recovery of cyanide and the repeatability of the method can be seen to be good. The mean recovery by the spectrophotometric method was 97.9% with a standard deviation of 1.24%. Corres- ponding figures for the gas-chromatographic method were 98.2% and 0.98%, respectively. For samples where both the spectrophotometric and gas-chromatographic methods were used a comparison of the results showed no significant difference between the procedures. No cyanide was detected in the unfortified feeds. Determination of Cyanide in Straight and Compound Feeding Stuffs Several straight feeding stuffs and a compound feeding stuff containing linseed expeller were examined by the proposed method.The results shown in Table I11 demonstrate the good repeatability of the method and the high level of agreement between the spectrophoto- metric and gas-chromatographic procedures.978 HARRIS et al. : DETERMINATION OF Anallyst, Vol, 105 As a further check on the recoveries of cyanide the method was applied to the products listed in Table I11 after fortification with amygdalin and linamarin ar concentrations equivalent to 10 mg k g l of CN-. Before these experiments could be conducted it was necessary to remove the cyanide arising from natural glycosides present. This was achieved by subjecting the products to the extraction and enzymatic hydrolysis procedures described above before adding known amounts of amygdalin and linamarin and then performing a second enzymolysis.Unfortified extracts treated similarly yielded no cyanide, indicating that the first enzymolysis was effective in removing all the cyanide initially present. The results of these experiments are given in Table IV and demonstrate the good recoveries given by the method. TABLE I1 RECOVERY OF CYANIDE FROM ANIMAL FEEDS FORTIFIED WITH AMYGDALIN AND LINAMARIN Feed (20.0-g sample) Glycoside Chick mash A . . Amygdalin Chick mash B Linamarin Linamarin Layers mash. . . . Amygdalin Linamarin Dairy ration containing approximately 18% m/m of rape meal Amygadlin Linamarin Spectrophotometric method GC method 7 r---.LL-- , ---A CN- added/ CN- found/ Recovery, CN- found/ Recovery, Pg Pg % Pg % 200 196 98.0 194 97.0 197 98.5 199 99.5 197 98.5 197 98.5 191 95.5 194 97.0 197 98.5 194 97.0 ~.~ 191 95.5 200 194 97.0 196 98.0 196 98.0 193 96.5 400 395 98.8 400 100.G 386 96.5 38 1 95.3 386 96.5 391 97.8 200 195 97.5 199 99.5 - _ _ 197 98.5 200 200 100.0 197 98.5 197 98.5 200 195 97.5 197 98.5 197 98.5 200 197 98.5 195 97.5 198 99.0 199 99.5 195 195 198 97.5 97.5 99.0 Liberation and Isolation of Cyanide In preliminary investigations the enzymatic hydrolysis was allowed to proceed for about 16 h at 37 "C in a sealed flask. At the end of this period the liberated cyanide was steam distilled from the reaction mixture under weakly acidic conditions. Although quantitative yields of cyanide from amygdalin and potassium cyanide were recorded in the absence of a feed matrix, the inclusion of such a matrix (ground wheat) reduced the recovery to 80-90% of the theoretical yield of cyanide.When potassium cyanide was added to ground wheat and the mixture was distilled immediately complete recovery of cyanide was obtained. These observations indicated the possibility of a reaction between the liberated cyanide and the feed matrix. If the cyanide could be removed from the reaction mixture whilst the enzymatic hydrolysis was in progress then improved yields might be obtained. An aeration technique was therefore employed with an air flow-rate of 1.5 1 min-l and the liberated cyanide collectedOctober, 1980 CYANIDE I N AXIMAL FEEDING STUFFS 979 in 0.5 11 sodium hydroxide solution. Improved yields were obtained but these were not consistent and on re-checking the yield of cyanide from amygdalin in the absence of a feed matrix a result of about IIOo/o was recorded using the spectrophotometric procedure.Further investigation showed that as a result of using an acetate buffer to maintain a pH of 5.0 (as recommended by the suppliers of the P-glucosidase enzyme used a t this stage of the work) TABLE 111 RESULTS OF ANALYSIS: CYANIDE CONTENT OF FEEDS AND NATURAL PRODUCTS CK- found/yg g-l r-------L------ 7 Spectrophotometric Matrix method GC method Expeller linseed . . . . 380, 392, 395, 392 385, 380, 378, 370 Feed containing 4% mjm linseed . . . . . . 8.6, 8.5, 8.3 8.6, 8.6, 8.9 Ground cassava tubers . . 159, 157, 150 - Sorghum (seeds) . . . . 1.5, 1.4, 1.5 - -4lfalfa . . . . . . . . 4.3, 4.0, 4.1 - acetic acid was being carried over during the aeration stage and was enhancing the absorbance readings.This effect could not be compensated for by making blank determinations as it only became manifest in the presence of cyanide. When the acetate buffer was replaced by a phthalate buffer at pH 5.0 the carry-over problem was eliminated. In applying the method to expeller linseed using phthalate buffers a t varying pH values, the maximum yield of cyanide was obtained at pH 7.0. Following the work of C ~ o k e , ~ the phthalate buffer was sub- sequently replaced by one containing potassium dihydrogen phosphate at pH 7.0. The method described by Cooke5 employs extraction of the cyano-substituted glycosides by orthophosphoric acid, thereby obviating the need for steam-distillation or aeration. Cooke's method did not appear to be wholly applicable t o animal feeding stuffs but the principle of extracting the glycosides from the feed before proceeding with the enzymatic hydrolysis aeration stage offered a further means of reducing the matrix effects discussed above.The orthophosphoric acid extraction stage was therefore combined with the aeration procedure and gave consistent, quantitative yields, as shown in the tables. TABLE IV RECOVERY OF CYANIDE FROM FEED MATERIALS FORTIFIED WITH AMYGDALIN AND LINAMARIN Matrix Glycoside Expeller linseed . . , . Amygdalin Linamarin Feed with 4% mjm linseed . . Amygdalin Linamarin Cassava . . . . . . Amygdalin Linamarin Sorghum (seeds) . . . . Amygdalin Linamarin Alfalfa . . . . . . . . Amygdalin Linamarin Recovery, yo r---------h------- 7 Spectrophotometric 95.7, 98.7, 97.4 96.4, 95.9, 97.3 98.0, 98.5, 99.6 94.2, 97.6, 97.4 96.3, 96.8, 99.1 - 95.9, 96.3, 97.1 - 97.8, 96.3, 96.9 - 95.6, 96.5, 95.0 - 92.3, 94.3, 95.1 - 93.9, 95.6, 96.2 - method GC method 96.5, 98.3, 97.1 97.1, 97.5, 96.9 97.3, 97.3, 96.4 95.9, 95.1, 96.7 Enzyme Sources The EEC method4 for cyanide in feeding stuffs prescribes the use of blanched sweet almonds as the enzyme source in the liberation of cyanide from the glycosides.As purified enzymes are now readily available it was decided a t the start of this work to use commercial P-D-glucosidase (E.C. 3.2.1.21) in place of the sweet almond suspension with a view to standard- ising the reagent. Although cyanide was liberated from expeller linseed in the presence of purified P-glucosidase, little or none was obtained from linamarin, the cyano-substituted glycoside of linseed.However, by using as the enzyme source an aqueous suspension of sweet almonds, good yields of cyanide were obtained from linamarin. The reasons for the980 HARRIS, MERSON, HARDY AND CURTIS very low yields of cyanide when p-D-glucosidase was used are not known, one explanation might be that in preparing the pure enzyme (from almonds) trace amounts of other materials, including enzymes necessary for the hydrolysis of linamarin, have been removed. The fact that some cyanide was liberated from expeller linseed in the presence of purified P-D-ghcosidase was undoubtedly due to the presence of endogenous enzymes, the added enzyme being superfluous to the reaction.From these observations it was concluded that in a general method. for the determination of cyanide in feeding stuffs, an enzyme system capable of acting on several glycosides must be present. The sweet almond suspension seems to supply the necessary range of enzymes and has therefore been retained in the proposed method in preference to pure enzyme sources. We thank the Government Chemist for permission to publish this paper. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. References Montgomery, R. D., in Liener, I. E., Editor, “Toxic Constituents of Plant Foodstuffs,” Academic Conn, E. E., in “Toxicants Occurring Naturally in Foods,” National Academy of Sciences Publication Council Directive 74/63 EEC, Oficial Jour.rta1 ofthe European Communities, L38, 1 l t h February 1974, Commission Directive 71/250 EEC, Oficial Journal of the European Communities, L155, 12th July Cooke, R. D., J . Sci. Food Agric., 1978, 29, 345. Wood, T., J . Sci. Food Agric., 1965, 16, 300. Blaedel, W. J., Easty, D. B., Anderson, L . , and Farrell, T. R., Anal. Chem., 1971, 43, 890. Winkler, W. O., J . Assoc. Off. Agric. Chem.. 1951, 34, 541. Bark, L. S., I n d . Chem., 1962 (October), 255. Bark, L. S., and Higson, H. G., Talanta, 1964, 11, 471. Department of the Environment, “Analysis of Raw, Potable and W%ste Waters,” HM Stationery Nota, G., and Palombari, R., J . Chromatogr., 1973, 84, 37. Nota, G., Palombari, R., and Improta, C., J . Chromatogr., 1976, 123, 411. Bates, B. L., and Buick, D. R., J . Assoc. Off. Anal. Chem., 1976, 59, 1390. Press, New York, 1969, p. 143. 1354, Natural Research Council, Washington, D.C , 1966. p. 31. 1971, p. 13. Office, London, 1972, p. 227. Received March 31st, 1980 Accepted May 28th, 1980

ISSN:0003-2654    

DOI:10.1039/AN9800500974

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

Analyst, October, 1980 981 SHORT PAPERS A Simple Non-dispersive Atomic-fluorescence Spectrometer for Mercury Determination, Using Cold-vapour Generation R. C. Hutton and B. Preston Tioxide Intervtational Limited, Central Laboratories, Stockton-on- Tees, Cleveland, TS18 2iVQ Keywords; Mercury determination; uapour generation; non-dispersive atomic- fluorescence spectrometry; estuarine samples The expansion of interest in environmental pollution has directed considerable effort towards obtaining lower limits of detection for many toxic elements. Analysis for mercury in par- ticular has placed considerable demands on currently available instrumentation and a recent review1 reflects the great analytical interest in this element. Both atomic-absorption and atomic-fluorescence techniques have been commonly employed to determine mercury and both have their advantages and disadvantage^.^-^ In our laboratory, we have for many years used an atomic-fluorescence technique.How- ever, demands for lower limits of detection coupled with the increased volume of samples presented for analysis have rendered our apparatus inadequate for present requirements. When deciding on a replacement, it was obvious from the number of samples analysed that one instrument would have t o be dedicated to mercury analysis. Rather than use an atomic- absorption procedure it was decided, after a review of the literature, that a purpose-built non-dispersive fluorescence instrument could achieve the levels required. The increased light-gathering power of a non-dispersive system is often off set by background scatter from the atom cell, usually a flame. However, cold-vapour generation gives minimum background scatter and considerable advantages could be obtained by using cold-vapour generation with a non-dispersive fluorescence system.Non-dispersive mercury fluorescence has been reported in the l i t e r a t ~ r e , ~ - ~ but in some instances5 the detection limits obtained required extreme conditions, e g . , solar-blind photomultipliers or sodium-lit rooms. This work describes the performance of a simple non-dispersive fluorescence spectrometer and its application to the routine analysis of marine samples. Non-dispersive fluorescence has not gained the popularity of dispersive techniques. Experimental Apparatus The instrument employed in this work was a purpose-built non-dispersive fluorescence spectrometer, illustrated schematically in Fig.1. The instrument was housed in a light-tight box with a partition in the centre separating the light source and fluorescence cell from the detection system. The fluorescence cell was a 10-mm 0.d. silica tube and fluorescence was measured at a height of 3 mm above the top of the tube. Source. Philips 02 4-W mercury-discharge bulb, powered by a laboratory-constructed 0.35-A constant-current power supply. Mercury cell. 10-mm 0.d. silica tubing, blackened both internally and externally to reduce reflected light. Slits. Photomultiplier. Photomultiplier power s u p p l y . Ampli$er. Chart recorder. 2 mm wide x 1 cm high. EM1 9781B (EM1 Electronics Ltd., Hayes, Middlesex) operated at 600 V.Bentham 215 high-voltage supply (Bentham Instruments Ltd., Reading, Berkshire). Bent ham 2 1 OE current-sensitive amplifier. Chessell flat-bed recorder (Chessell Ltd., Worthing, Sussex).982 SHORTPAPERS Analyst, VoZ. 105 Reagents Dissolve 100 g of tin(I1) chloride in 500 ml of con- centrated hydrochloric acid and dilute to 1 1 with distilled water. Add 25 ml of concentrated sulphuric acid and 110 ml of concentrated hydrochloric acid to 50 ml of distilled water. Dissolve 1.08 g of mercury(I1) oxide in the minimum volume of 1 + 1 V/V hydrochloric acid and dilute to 1 1 with distilled water. Procedure Tin(I1) chloride solution (5 ml) and 5 ml of acid solution were placed in the reduction cell. Argon was bubbled through the solution a t 1.5 1 min-l to remove residual mercury.A suitable aliquot of sample solution (usually 1 or 5 ml) was placed in the reactor cell using a micropipette and the fluorescence signal was read off on a chart recorder. The tin(I1) chloride solution was renewed after every 5-10 determinations, depending on mercury levels. Tin(11) chloride solution, 10% m/V. Acid solution. Mercury standard, 1000 pg ml-1 of mevcury. Cool and dilute to 100 ml. A procedure similar to that of Hatch and OttlO was employed. To recorder Fig. 1. Schematic layout of non-dispersive fluorescence system. A, Rotameter; B, 125-ml capacity reaction cell; C, fluorescence cell; D, mercury discharge bulb; E, slits on central paIti- tion; F, optical guide; G, photomultiplier; H, 0.35-A constant current power supply; I, exit to vacuum line.Results and Discussion The instrumental layout illustrated in Fig. 1 was the result of careful optical optimisation, which led to the lowest possible background light levels. It was found preferable, for example, to use an optical guide (a 15-mm diameter brass tube) rather than a lens between the slits and the photomultiplier tube. Reflections from lenses were found to degrade the signal to background ratio. The central partition, separating the source and the fluorescence cell from the photomultiplier, was necessary to reduce stray light from the source. A reduction in background from the source of approximately 300-fold was achieved with the partition in place, giving an approximate source background equivalent t o 0.005 pg 1-l.Possible molecular background from ozone, generated by the mercury discharge bulb, was eliminated by slight suction, which also removed residual mercury vapour from the instrument. The calibration graphs obtained are illustrated in Fig. 2. These sliow a linear response from the detection limit to over 100 pg l-l, over three orders of magnitude. A practical detection limit of 0.04 pg 1-1 was determined by monitoring continuous day-to-day variations on a 1-ml sample containing 1 pg 1-1 of mercury. A typical precision run using 1 ml of a sampleOctober, 1980 SHORT PAPERS 983 containing 1 p g 1-1 of mercury with an amplifier time constant of 1 s gave the following results (chart divisions): 43, 43, 43, 45, 43, 42, 44, 42, 44. These results give a mean of 43.2 chart divisions with 26 = 0.045 pg 1-1 and a coefficient of variation = 2.25%.Precisions of 2-3% can be achieved. Greater sensitivity could be obtained by the use of up to 5 ml of sample solution, but in general this was found not to be necessary. The detection limit obtained statistically also represents approximately twice the total blank signal obtained practically. 1. i- .- to3 i- C W t .- 8 ; 102 0 - ‘c 5: -I 10 *‘ I x’ 0 0 1 1 10 100 Mercury concentration/pg I-’ Fig. 2. Calibration graphs for mercury fluorescence on logarithmic co-ordinates. A, 1-ml sample volume; B, 5-ml sample volume. The performance of this instrument compares favourably with that of other vapour genera- tion systems previously reported, without requiring complex instrumentation.The instru- ment could possibly be improved further by the inclusion of a solar-blind response photomultiplier, but the practical problems associated with working at such low mercury levels may outweigh the expense involved in the purchase of such a tube. The instrument has been routinely used to determine mercury levels in acid extracts of estuarine sediments and shrimps. Comparison of results obtained by dispersive fluorescence show that no disadvantages result from the use of a non-dispersive system and that lower blank levels can be quoted with confidence, owing to the increased sensitivity. This is illustrated in Table I, which gives results obtained from a typical sample batch. The in- strument can typically analyse 30-40 samples per hour (including standards and blanks).TABLE I COivlPARISON OF DISPERSIVE AND NON-DISPERSIVE DETERMINATION OF MERCURY IN EXTRACTS FROM ESTUARINE SEDIMENTS AXD SEA SHRIMPS Sample volume = 1 ml. Mercury concentration/pg 1-1 Blank .. .. 1 . . . . 2 . . . . 3 . . . . 4 . . .. 5 . . . . 6 . . . . 7 . . . . 8 . . . . e . . . . 10 .. .. Sediments Dispersive hTon-dispersive <1 <0.05 14 10 16 7 12 11 6 6 9 10 9 12 Shrimps r---_h ---_ Dispersive Non-dispersive <1 t0.05 3 4 3 3 3 3 3 3 8 6 4 3 3 4 3 4 3 4 7 - -984 SHORT PAPERS Conclusion Analyst, Vol. 105 It has been demonstrated that by careful optical optimisation, a simple inexpensive non- dispersive mercury fluorescence spectrometer can achieve detection limits comparable to those obtained with more complex systems. The instrument is both sensitive and precise and allows a rapid throughput of samples without the need to alter the operating conditions frequently. The authors acknowledge the help of Mr. L. Best with the fabrication of the spectrometer. This work is published by permission of the Directors of Tioxide Inteirnational Limited. References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Ure, A. M., Anal. Chim. Acta, 1975, 76, 1. Thompson, K. C., and Reynolds, G . D., Analyst, 1971, 96, 271. Muscat. V. I.. and Vickers. T. T.. Anal. Chim. Acta. 1971, 57, 23. Thomerson, D. R., Int. Lab., 1377 (January), 57. Caupeil, J . E., Hendrikse, P. W., and Bongers, J. S., Anal. Chim. Acta, 1976, 81, 53. Rigin, V. I., 21. Anal. Khim., 1979, 34, 261. Shimomura, S., and Hiroto, R., Anal. Lett., 1973, 6, 613. Thompson, K. C., Lab. Pract., 1972, 21, 645. Nakahara, T., Tanaka, T., and Musha, S., B d l . Chem. Soc. Jpn., 1978, 51, 2020. Hatch, W. R., and Ott, W. L., Anal. Chem., 1968, 40, 2085. Received March 25th, 1980 Accepted May 16th, 1980

ISSN:0003-2654    

DOI:10.1039/AN9800500981

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

984 SHORT PAPERS Analyst, Vol. 105 Determination of Sulphide in Flooded Acid - Sulphate Soils by an Indirect Atomic-absorption Spectrophotometric Method Ramesh C. Ray, P. K. Nayar, A. K. Misra and N. Sethunathan Division of Soil Science and Microbiology, Central Rice Research Institute, Cuttack-7 53006, India Keywords: Flooded acid - sulphate soils; sulphide determination; atomic- absorption spectrophotometry Hydrogen sulphide, evolved during the anaerobic metabolism of sulphate, is readily converted into insoluble metal sulphides, chiefly iron(I1) sulphide, in flooded acid - sulphate soils that are especially rich in ir0n.l The widely used method for determining sulphide is based on the precipitation of the sulphide in hydrogen sulphide as zinc sulphide and subsequent determina- tion by methylene blue formation2 or t i t r i m e t r ~ .~ The simple, rapid and reproducible method described here essentially involves the precipitation of zinc sulphide by the action of zinc on the hydrogen sulphide liberated on acidification of metal sulphides in flooded acid - sulphate soils, and then indirect determination of sulphide by determining the zinc in the precipitate and also the zinc remaining in solution, after the precipitation, by atoniic-absorption spectro- photometry. Experimental The assembly used for the conversion of metal sulphides into hydrogen sulphide consisted in a 250-ml Erlenmeyer flask, which was closed with a three-hole rubber bung, for holding a dropping funnel (for adding hydrochloric acid) and two glass tubes (an inlet for oxygen-free nitrogen and an outlet).The outlet was connected to two 100-ml Erlenmeyer flasks, in succession, containing an ammoniacal solution of zinc acetate to trap the hydrogen sulphide evolved. For standardisation of the method, a known amount of sodium sulphide was placed in a 250-ml flask and then treated with 100 ml of 1 N hydrochloric acid. The hydrogen sulphide evolved was swept into the zinc acetate solution with oxygen-free nitrogen forOctober, 1980 SHORT PAPERS 985 30 min-1 h (until tests with lead acetate paper strips showed complete cessation of hydrogen sulphide evolution) in order to precipitate zinc sulphide. Zinc sulphide was accumulated in the first trap while the second trap was visibly free from any precipitate; this indicated that hydrogen sulphide was completely precipitated in the first trap.After filtration, the precipitated zinc and soluble zinc remaining in the filtrate were assayed using a Varian Techtron atomic-absorption spectrophotometer, Model AA-1100. Sulphide equivalent to the zinc precipitated or to the decrease in the zinc content of the solution was then calculated. Care was taken to ensure that the molar concentration of sulphide was far exceeded by the molar concentration of zinc in order to provide a measurable excess of zinc in solution after complete precipitation of the sulphide. This method was compared simul- taneously with the conventional iodimetric m e t h ~ d , ~ in which the zinc sulphide precipitated in the trap was reacted with excess of iodine plus 2.5 ml of concentrated hydrochloric acid and the unreacted iodine was titrated against standard thiosulphate solution.Sulphide formed in two acid - sulphate soils, Pokkali (pH, 5.0; organic carbon, 2.28%; sulphate-S, 0.056%; total sulphur, 0.1%) and Kari (pH, 3.9; organic carbon, 4.65%; sulphate- S, 0.039%; total sulphur, 0.13%) under flooded conditions was determined by atomic- absorption spectrophotometry and iodimetry. Soil samples (20 g) were flooded with 25 ml of distilled water in test-tubes (25 x 200 mm). After 40 d, the reduced soil samples were transferred into 250-ml flasks and treated with 100 ml of 1 N hydrochloric acid in order to liberate hydrogen sulphide from the metal sulphides, chiefly iron(I1) sulphide. Hydrogen sulphide was absorbed in an ammoniacal solution of zinc acetate with precipitation of zinc sulphide.The zinc in the precipitate and the filtrate was determined by atomic-absorption spectrophotometry to give the result for the indirect determination of sulphide. Care was taken to bubble oxygen-free nitrogen through the apparatus for 5 min prior to acidification of the soil samples to prevent the instantaneous oxidation of the hydrogen sulphide evolved in the flask. The sulphide was also determined by the conventional iodi- metric method3 by adding excess of iodine plus hydrochloric acid directly to the trap as described for the sulphide determination from sodium sulphide in the standardisation of the method. In a modification of this method, the precipitated zinc sulphide was first separated by filtration and then treated with excess of iodine plus hydrochloric acid to avoid any inter- ferences from iodine consuming substances, if any, from the complex soil system.Results and Discussion The data in Table I showed that about 85% of sulphide was recovered from sodium sulphide standards by both the iodimetric and atomic-absorption spectrophotometric methods. Also, in the latter method, the sulphide values, obtained by determining the zinc either in the zinc sulphide precipitated or that remaining in solution in the filtrate, were almost identical. The atomic-absorption spectrophotometric method was simple, rapid and reproducible with variations of less than 5% within replicates, while the iodimetric method, though equally sensitive, was somewhat tedious.TABLE I SULPHIDE RECOVERED FROM SODIUM SULPHIDE STANDARDS The results are for sulphide recovered. Atomic-absorption spectrophotometry Result from determination of Result from determination of zinc in filtrate zinc in precipitate Iodimetry r- 7 -7 Sulphide Replicate/ Mean/ Recovery, 'Replicate/ &lean/ Recovery, ' Replicate/ Mean/ Recover; added/mg mg mg % mg mg % mg mg % 82.8 2.86) 2.86 84.8 :%} 2.86 84.8 2.85 2.87, 2.84 3.37 2.70 4.49 ::ti} 3.71 82.6 E} 3.75 83.5 84.0 2.79 J 3.83 3.76 3.66 The determination of sulphide in two acid - sulphate soils after a 40-d flooding showed that the sulphide values from both soils were realistic and reproducible, ranging from 0.26 to986 SHORT PAPERS Analyst, VoZ. 105 0.33 mg g-l when determined by atomic-absorption spectrophotornetry (Table 11).As in the pure system when sodium sulphide was used, soil sulphide levels derived from the determination of zinc either in the precipitate or in the filtrate were identical. However, the iodimetric method in which iodine was added directly to the trap gave abnormally high sulphide values (> 1.36 mg g1) for both soils; these levels are above the theoretical values for sulphide that could be generated from Pokkali soil with 0.056% sulphate-S and 0.1% of total sulphur and from Kari soil with 0.039% sulphate-S and 0.13% of total sulphur following flooding. However, the sulphide content of the Kari soil, obtained by the modified iodimetric method, in which the zinc sulphide was treated with iodine only after filtration, was realistic, reproducible and identical with that obtained by atomic-absorption spectrophotometry.This would suggest that overestimation of soil sulphide, by the con- ventional method of adding iodine directly to the trap, was a result of interferences by some reduction products of the flooded soil system. For instance, reduced sulphur compounds TABLE I1 SULPHIDE FORMED IN ACID - SULPHATE SOILS ON 40-d FLOODING The results are for sulphide formed in mg per gram of soil. Atomic-absorption spectrophotometry r-----L------ _7 determination of determination of Iodim e t ry 7 Result from Result from _______ A _______-_ zinc in filtrate zinc in precipitate Conventional* Precipitate? 7 ---- 7 - r---dL ‘-+--- r---- Soil Replicate Mean Replicate Mean Replicate Mean Replicate Mean N.D.$ Pokkali .. ::ti\ 0.29 ::;;\ 0.29 ::!:\ 2.03 N.D. 0.28J 0.30) 1.85) N.D. E} 1.65 0.32 1.56 0.33 Kari . . :::!} 0.28 ::ti} 0.29 0.26 0.29 Iodine was added directly to the trap. t Zinc sulphide precipitated was first separated by filtration and then treated with iodine. N.D. not determined. such as sulphite, thiosulphate, tetrathionate and hydrosulphike rnay decompose during acidification leading to erratic results in the determination using i ~ d i m e t r y . ~ Likewise, the methylene blue method, widely used in determining sulphide, is not always reliable as not only hydrogen sulphide but other reduction products that commonly occur in anaerobic ecosystems can readily react with methylene blue to produce erroneous results. The new method of indirect determination of sulphide through the determination of zinc by atomic- absorption spectrophotometry is simple, rapid and free from interference and thus has a definite advantage over the iodimetric and methylene blue methods, especially in a complex system such as waterlogged soil. The authors are grateful to Dr. H. K. Pande (Director) for encouragement, Dr. S. Patnaik and Dr. C. C. Biddappa for suggestions and Dr. S. B. Lodh for facilities. This project was partially funded by the Department of Science and Technology, Government of India, and the International Atomic Energy Agency, Vienna. 1. 2. 3. References Ponnamperuma, F. N., Adv. Agron., 1972, 24, 29. Johnson, C. M., and Nishita, H., Anal. Chem., 1952, 24, 736. American Public Health Association and Water Pollution Control Federation, “Standard Methods for the Examination of Water and Waste Water,” Thirteenth Edition, American Public Health Association, New York, 1971, p. 551. Received April lst, 1980 Accepted May 8th, 1980

ISSN:0003-2654    

DOI:10.1039/AN9800500984

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

October, 1980 SHORT PAPERS 987 Determination of Diuron Residues in Soil: Comparison of Determinations by High-performance Liquid Chromatography and Gas - Liquid Chromatography E. G. Cotterill .4gricultural Research Council Weed Research Organization, Begbroke Hill, Yarnton, Oxford OX6 1PF Keywords: Diuron determination; soil; gas - liquid chromatography; high- performance liquid chromatography The herbicide diuron [N-(3,4-dichlorophenyl)-NN-dimethylurea] is used for the control of annual weeds in fruit crops and total weed control in non-crop situations. Substituted urea herbicide residues have been determined using gas - liquid chromatography (GLC) by pyrolysis to the phenyl isocyanate in the injection heater192 with electron-capture detection. They have also been determined by high-performance liquid chromatography (HPLC)3-6 and by GLC using a thermionic detector.' Lawrence and Lavers and Biichert and Lokke9 have re- ported methods using GLC determination after alkylation.Bieser and Grolinmundlo and Khan et a1.l1 have devised methods of measuring urea herbicides by GLC without thermal decomposition. The aim of the work reported here was to determine the most reliable method of measurement for the routine determination of diuron residues in soil. Experimental Soils Table I gives some details of the soil composition a t each site. Each soil was air dried and passed through a 3-nim sieve prior to fortification. Aqueous solutions of diuron were prepared from a meth- anolic solution containing 1 mg ml-l of herbicide so that, when sufficient solution was added to the soil to achieve 75% water-holding capacity, the concentration of herbicide in soil was 1.0, 0.5 or 0.1 pg g-l.Soils were fortified in triplicate and allowed to stand for 48 h before analysis. A sample from the top 10-15 cm was taken with a shovel 1 month after application and sieved. After thorough mixing the soil was split into 12 sub-samples and stored wet a t -15 "C until analysis. TABLE I SOME PROPERTIES OF THE SOILS USED Soils from three locations were used for the fortification studies. In addition, an area at site 1 received a field application of diuron a t 1 kg ha-1. Soil 1 2 3 Organic carbon, % . . . . 1.6 4.1 25 Clay, % . . . . . . 16 16 56 Silt, % . . . . . . . . 11 16 32 Water-holding capacity, % . . 16.6 27.0 38.9 Property ---------l pH .. . . . . . . 7.0 5.1 5.9 Sand, yo . . . . . . 73 68 12 Extraction The method of McKonel was used. methanol by shaking on a wrist-action shaker for 1 h. through a Watman No. 42 filter-paper. by gently blowing dry air and the residue was re-dissolved in 2 ml of hexane. A 25-g sample of soil was extracted with 50 mi of The resulting soil slurry was filtered For GLC, a 2-rnl aliquot was evaporated to dryness For HPLC, a988 SHORT PAPERS Analyst, Vol. 105 25-ml aliquot was concentrated to about 1 ml under reduced pressure whilst warming in a water-bath at 40 "C. The remaining solvent was removed with a gentle stream of dried air and the residue was then re-dissolved in 1 ml of the HPLC eluent. Chromatography Gas - liquid chyomatogaphy A Pye 104 chromatograph fitted with a nickel-63 electron-capture detector and a 1.5 m x 4 mm i.d. glass column was used.The conditions employed were as follows: column packing, 5% SE-30 on Chromosorb W HP (80-100 mesh); carriw gas, oxygen-free nitrogen at a flow-rate of 50 ml min-l; column temperature, 155 "C; injector temperature, 250 "C; detector temperature, 350 "C; attenuation, 10 x lo2; and pulse width 150 ps. Standard solutions with concentrations in the range 0.05-1.0 ng per 5-p1 injection gave a linear response, the peak area being determined with a Perkin-Elmer Sigma 10 chromato- graphy data station. High-performance liquid chyomatogaphy A constant-flow pump (HSCP, Bourne End, Buckinghamshire) was connected to a 100 mm x 5 mm i.d. stainless-steel column packed with Hypersil-OD!< (5.5 ,um mean diameter) (Shandon Southern).Injections were made using a Rheodyne valve and diuron was measured using a Cecil 212 variable-wavelength ultraviolet monitor set at 250 nm and 0.1 absorbance unit for full-scale deflection. Methanol - water (7 + 3) was used as the eluent at a flow-rate of about 0.5 ml min-1. Standards in the range 5-50 ng per 5 . ~ 1 injection gave a linear response, the peak area being determined with a Perkin-Elmer Sigma 10. The optimum absorption wavelength was determined by scanning a diuron solutijon between 200 and 300 nm prior to chromatography. Results and Discussion An initial experiment showed that the GLC conditions selected, although causing pyrolysis in the injection heater, gave more reproducible results than when conditions were arranged so as to avoid thermal degradation.As the aim of the work was to produce a routine method, derivatisation techniques were not included as they extend the analysis time. TABLE I1 RECOVERY OF DIURON FROM SOIL HPLC GLC Method . . .. . . . . Diuron added/ Soil pg g-1 1 1 .o 0.5 0.1 2 1.0 0.5 0.1 3 1.0 0.5 0.1 98.8, 99.9, 101.4, 101.9, 101.0, 104.5, 87.9, 89.3, 98.8, Recovery, y, 95.3, 102 3 99.9, 92 0 98.8, 96 2 100.0. 98 1 99.4, 97 9 100.9, 80 1 102.1, 104 9 92.0, 86 6 93.5, 87 3 1 1.0 99.6, 97.3, 94.7 0.5 90.1, 84.8, 96.0 0.1 84.7, 96.5, 96.1 2 1.0 102.2, 93.2, 84.5 0.5 96.8, 90.5, 84.6 0.1 73.4, 97.5, 85.5 Not analysable without clean-up 3 0.1 Mean 98.8 97.2 98.8 100.0 99.4 94.7 98.3 89.3 93.5 97.2 90.3 92.4 93.3 90.7 85.4 recovery, yo Table I1 shows the recovery of diuron from fortified soil using HPLC and GLC determina- tions.There is no practical difference between the means obtained by either method but the variance within the means is greatest for GLC determination. The results obtained from theOctober, 1980 SHORTPAPERS 989 12 sub-samples from the area treated in the field showed a mean of 0.13 pg g-l and a co- efficient of variation of 11.5% for HPLC determination and a mean of 0.12 g g-l and a coefficient of variation of 41.7% for GLC determination. Thus, although the means are almost the same, the variability of the GLC determination is over three times that of HPLC. Fig. 1 shows high- performance liquid chromatograms of (a) 20ng of diuron, ( b ) extract of soil 1 treated at 0.1 pg g-1 and (c) extract of soil 3 treated at 0.1 pg g-l, and Fig.2 shows gas - liquid chroma- tograms of (a) 1.0 ng of diuron, (b) extract of soil 1 treated at 0.1 pg g-l and (c) extract of A further advantage of HPLC over GLC is shown in Figs. 1 and 2. Time --+ Fig. 1. High-perform- ance liquid chromato- grams of (a) 20 ng of diuron : ( b ) extract of soil 1 treated a t 0.1 pg g-1; and (c) extract of soil 3 treated a t 0.1 pg g-1. Time --b Fig. 2. Gas - liquid chroma- trograms of (a) 1.0 ng of diuron; (b) extract of soil 1 treated a t 0.1 p g g-l; and (c) extract of soil 3 treated a t 0.1 pg g-l. soil 3 treated at 0.1 pg g-l. Hence diuron can be analysed by HPLC in a soil with a high organic matter content without clean-up, so avoiding the extra manipulations and possible introduc- tion of errors and the increased analysis time that would be required if the same soil was analysed by GLC.Fig. 2 also shows extensive peak tailing, indicative of breakdownof diuron on the column. As substituted ureas break down to the corresponding phenyl iso- ~ y a n a t e , ~ ? ~ diuron and its metabolites N-(3,4-dichlorophenyl)-N-methylurea (DCPMU) and N-(3,4-dichlorophenyl)urea (DCPU) all elute from a GLC column as 3,4-dichlorophenyl isocyanate. Hence the parent compound cannot be distinguished from its metabolites using GLC, whereas HPLC will separate all of these compounds, with retention times for diuron, DCPMU and DCPU of 4.1, 7.5 and 6.7 min, respectively, using the conditions given. Although HPLC is generally the most reproducible method, GLC has the advantage of being more sensitive.When measuring very low residues in soils with a low organic matter content, GLC could prove to be the better method but the results should be interpreted with caution because of the possible presence of unresolved metabolites. In practice, however, the limit of detection is set by the signal to background ratio, which is usually similar for both methods, but in the more organic soils HPLC is favoured. A limit of detection of 0.04 pg g-l can be achieved using either method. References 1. 2. 3. 4. McKone, C. E., J . Chromatogr., 1969, 44, 60. Spengler, D., and Hamroll, B., J . Chromatogr., 1970, 49, 205. Lawrence, J. F., J . Assoc. Off. Anal. Chem., 1976, 59, 1066. Sidwell, J. A,, and Ruzicka, J. H. A,, Analyst, 1976, 101, 111990 SHORTPAPERS Analyst, Vol. 105 5. 6. 7. 8. 9. 10. 11. Byast, T. H., J . Chromatogr., 1977, 134, 216. Pribyl, J., and Herzel, F., J . Chromatogr., 1978, 166, 272. Jarczyk, H. J., P~anzenschutz-Nachr., 1976, 28, 334. Lawrence, J. F., and Laver, G. W., J . Agric. Food Chem., 1975, 23, 1106. Biichert, A,, and Lokke, H., J . Chromatogr., 1975, 115, 682. Bieser, H., and Grolinmund, K., J . Assoc. Off. Anal. Chem., 1974, 57, 1294. Kahn, S. U., Greenhalgh, R., and Cochrane, W. P., Bull. Environ. Contnm. Toxicol., 1975, 13, 602. Received March 31st, 1980 Accepted April 24th, 1980

ISSN:0003-2654    

DOI:10.1039/AN9800500987

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

990 SHORTPAPERS Analyst, Vol. 105 Rapid Extraction of Some Persistent Chlorinated Hydrocarbons from Biological Material with Low Fat Content Gunnar Norheim and Elisabet Mo Okland National Veterinary Institute, P.O. Box 8166 De#., Oslo 1, Norway Keywords: Chlorinated hydrocarbon extraction; hexachlorobenzene; octachloro- styrene; biological material; low f a t content Persistent chlorinated hydrocarbons of agricultural and non-agricultural interest, such as l,l,l-trichloro-2,2-bis-(p-chlorophenyl)ethane (DDT), polychlorinated biphenyls (PCBs) and hexachlorobenzene, have obtained a global distribution, and can be detected in wildlife samples in variable amounts. PCBs together with l,l-dichlc~ro-2,2-bis-(~-chlorophenyl)- ethylene (DDE) are the main types of chlorinated hydrocarbons found in Norwegian avian fauna and in fish along the Norwegian In Frierfjorden, a fiord in South-Eastern Norway, heavy local contamination with chlo- rinated hydrocarbons of industrial origin has been detected.The contaminants most often found in the fish in this area are hexachlorobenzene, octachlorostyrene and decachlorobiphenyl. In addition, complex mixtures of PCBs and also of chlorinated naphthalenes have been detectede415 Decachlorobiphenyl has previously been detected in. arctic fox ( A l o p e x lagopus) from Svalbard,6 and octachlorostyrene was first detected in birds from The Netherlands. '18 In a monitoring programme over the last 6 years, the above chlorinated hydrocarbons have been determined in samples from cod (Gadus morhua) obtained from the area.Flesh samples from cod have a low fat content (about 0.3%) and extraction of such samples is not especially reproducible. Some procedures are also very time consuming. A rapid and simple procedure has therefore been developed for this type of sample for the gas-chromatographic determina- tion of some chlorinated hydrocarbons resistant to concentrated sulphuric acid. Experimental Apparatus and a 2 m x 3 mm i.d. glass column was used. 15.9% SP-2401 on 100-120-mesh Supelcon AW DMCS. temperatures were 200, 250 and 275 "C, respectively. the carrier gas, the flow-rate being 55 ml min-l. Reagents A Carlo Erba 2100 gas chromatograph equipped with a nickel-83 electron-capture detector The column material was 1.5% SP-2250 - The column, injector and detector Argon - methane (95 + 5 ) was used as The electrometer attenuation was x 128.S u l p h u r i c acid, 95-97%. Heptane. Pro analysi grade (Merck). Hexachlorobenzene. Pract. grade (Fluka) . octachlorostyrene. Standard Solutions Amounts of 100 mg each of hexachlorobenzene and octachlorostyrene were dissolved in 100 ml of heptane and the mixture was diluted 1 + 50000 with heptane. Pro analysi grade (Merck). Obtained as a gift from Norsk Hydro.Gctober, 1980 SHORT PAPERS 99 1 Procedure A 0.5-g amount of sample was accurately weighed into a 10-ml Soveril glass tube fitted with a screw-cap, and 6 ml of concentrated sulphuric acid were measured into the tube. The tube was placed in a thermostatically controlled oven a t 60 "C for 4 h, during which time it was shaken lightly a few times to ensure complete solubilisation of the sample.After cooling, 1.0 ml of heptane was pipetted into the tube, the screw-cap put on and the tube shaken for about 3 min. Finally, the tube was centrifuged with the screw-cap on, after which the sample was ready for gas chromatography. An injection volume of 5 p1 was used. TABLE I RECOVERY OF HEXACHLOROBEKZEKE (HCB) AND OCTACHLOROSTYRENE (OCS) FROM HOMOGENISED COD FLESH AFTER ISOLATION BY THE PROPOSED METHOD AND EXTRACTION WITH DRY DIETHYL ETHER OR HEXANE - PROPAN-8-OL Recovery, yo r--L- Method HCB ocs\ Present method . . . . . . 95 95 Dry diethyl ether . . . . . . 32 58 Hexane - propan-2-01 . . . . 87 86 Results and Discussion The proposed method is rapid and requires only small amounts of reagents and little equipment.The recoveries of hexachlorobenzene (HCB) and octachlorostyrene (OCS) were determined after a standard addition by a method described previou~ly.~ The recovery of each component was 95%. A large number of samples can be extracted simultaneously. i C B l ocs ocs - 0 4 8 0 4 8 0 4 8 Time/min Fig. 1. Chromatograms of 5-p1 injec- tions of hexachlorobenzene (HCB) and octachlorostyrene (OCS). (a) Standard solution of HCB and OCS (0.1 ng of each) ; ( b ) extract of cod flesh from a contami- nated area (in addition to HCB and OCS this chromatogram has peaks for penta- chlorobenzene and heptachlorostyrene) ; ( c ) extract of a blank sample of cod flesh. The gas-chromatographic conditions are stated in the text.992 SHORT PAPERS Analyst, Viol. 105 TABLE I1 RESULTS OF A COLLABORATIVE STUDY IN WHICH PENTACHLOROBENZENE (5CB), HEXACHLOROBENZENE (HCB) AND OCTACHLOROSTYRENE (ocs) WERE DETERMINED IN HOMOGENISED COD FLESH Concentration/yg 8-l (wet mass) Laboratory 5CB HCB OCS This work .. . . 0.002 0.13 3.7 Laboratory 2 . . . . 0.003 0.17 4.2 Laboratory 3 . . . . 0.002 0.10 1.3 Laboratory 4 . . . . - 0.08 1.3 Laboratory 1 . . . . 0.001 0.10 3.7 The recovery of HCB and OCS from homogenised cod flesh using the proposed method was compared with two other methods, namely column extraction with dry diethyl etherlo and direct extraction for 4 h with hexane - propan-2-01 and subsequent partition with water.4 The results are presented in Table I. The reproducibility of the method was calculated after the determmation of HCB and OCS in eight parallel samples of cod flesh.The following results were obtained after manual injection of the extracts into the gas chromatograph: HCB, 0.25 & 0.014 pg g-l; and OCS, 0.18 f 0.017 pg g-1. The coefficients of variation for HCB and OCS were 5.5% and 9.5%, respectively. The retention time under the conditions used was 1.6 min for HCB and 4.5 min for OCS. Typical gas chromatograms are presented in Fig. 1. A blank sample from a non-contaminated area gave no interfering peaks. The accuracy of the proposed method was tested in a collaborative study involving five laboratories.11 The other four laboratories used other extraction procedures. The results of this study are presented in Table 11. Agreement was fairly good for HCB, but less good for OCS, two of the laboratories finding lower levels. The method was also tested on homo- genised herring containing about 10% of fat, and agreement with the results of ordinary extraction techniques was better than that for the cod flesh, especially for OCS.With increasing fat content in the sample, emulsion formation after the extraction with heptane causes problems. This may be partly overcome by increasing the volume of heptane, although sensitivity is thereby decreased. Heptane was preferred to hexane as the solvent because of its lower volatility. However, if a high reproducibility is to be achieved, it is essential that centrifugation be carried out with the screw-cap on. The sensitivity of the method is dependent on the gas-chromatographic equipment used.In our laboratory we can routinely determine HCB and OCS in cod flesh at levels down to 0.001 pg g-l wet mass. An important limitation of the proposed method is that DDE is partly broken down during the digestion and cannot be determined accurately. PCB:j, on the other hand, can be recovered as efficiently as HCB and OCS. In our studies on HCB, OCS and decachlorobiphenyl in fish from Frierfjorden and the surrounding fiords, the proposed method has proved useful in the gas-chromatographic determination of these chlorinated hydrocarbons. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. References Holt, G., Fralie, A,, and Norheim, G., Acta Vet. Scand., 1979, Suppl. 70, 28 pp, Brevik, E. M., Bjerk, J. E., and Kveseth, N. J., Bull. Environ. Contam. Xoxicol., 1978, 20, 715. Kveseth, N. J., Bjerk, J. E., Fimreite, N., and Stenersen, J., Arch. Environ. Contam. Toxicol., 1979, Lunde, G., and Baumann Ofstad, E., Fresenius 2. Anal. Chem., 19768, 282, 395. Baumann Ofstad, E., Lunde, G., Martinsen, K., and Rygg, B., Sci. Total Environ., 1978, 10, 219. Norheim, G., Acta Pharmacol. Toxicol., 1978, 42, 7. Koeman, J . H., ten Noever de Brauw, M. C., and de Vos, R. H., Natuve (London), 1969, 221, 1126. ten Noever de Brauw, M. C., and Koeman, J . H., Sci. Total Environ., 19'72/73, 1, 427. Norheim, G., and 0kland, E., paper presented at Workshop in Gas Chromatography, Sandefjord, Bjerk, J. E., and Holt, G., Acta Vet. Scand., 1971, 12, 429. Martinsen, K., Baumann Ofstad, E., Lunde, G., Brevik, E. M., Kveseth. N. J., Bse, B., Egaas, E., 8, 201. Norway, 1978. Crowo, J . A., Murer, K., Frmlie, A., and Norheim, G., Report, Oslo, Norway, 1978. Received May 6th, 1980 Accepted May 29th, 1980

ISSN:0003-2654    

DOI:10.1039/AN9800500990

出版商:RSC    

年代:1980

数据来源: RSC

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October, 1980 SHORT PAPERS 993 Determination of the Anthelmintic Levamisole in Plasma and Gastro-intestinal Fluids by H ig h-perf ormance Liquid Chromatography S. Marriner, E. A. Galbraith and J. A. Bogan Department of Veterinary Glasgow, G61 IQH Pharmacology, University of Glasgow Veterinary School, Bearsden Road, Bearsden, Keywords; Levaimisole determination; biological juid analysis; high- pevforwalzce liquid chromatography Levamisole (1-tetramisole, 2-[2,3,5,6-tetrahydro-6-phenylimidazo(2,l-b)thiazole] } is commonly used in many species of animal as an anthelminti~~l-~ Levamisole has been determined in cattle tissues and milk by differential cathode-ray polarography, a technique which is not available in most chemical laboratories and which lacks sensitivity. Gas - liquid chromatography has also been used for levamisole determina- tion in milk7 but this method requires a lengthy clean-up procedure using organic solvent extraction and the use of a selective alkali flame-ionisation detector.High-performance liquid chromatography (HPLC) appeared to offer a more suitable technique for the determination of levamisole and in this work a sensitive and rapid method using this technique is described. Experimental Reagents All reagents were of analytical-reagent grade. Diethyl ether. Borate buffer, $H 9. Hydrochloric acid, 0.1 N. Sodium hydroxide solution, 1.0 N. Methanol. Re-distilled before use. Ammonium carbonate soldon, 0.05 M. Solution A: dissolve 0.746 g of potassium chloride and 0.618 g of Mix boric acid in 180 ml of distilled water. solutions A and B in the approximate proportions of 9 to 1 to give a solution of pH 9.Solution B: 0.2 N sodium hydroxide solution. HPLC Apparatus Pump. Altex, Model 110. Detector. Column. Packing. ODS Hypersil (Shandon Southern). Wavelength. 220 nm. Absorbance. 0.1 a.u.f.s. Solvent. Flowrate. 1.0 ml min-l. Under these conditions levamisole had a retention time of 2.7 min. Cecil, Model CE 2012, variable-wavelength spectrophotometer. 100 x 5 mm (Shandon Southern). Methanol - ammonium carbonate solution, 0.05 M (65 + 35). Procedure add 2 ml of pH 9 borate buffer and 15 ml of diethyl ether. 10 min on a slow rotary mixer. ground glass stoppered test-tube using a 5-ml adjustable pipette. must be pre-wetted with the ether before accurate transfer can be effected.) 15 ml of ether to the first tube and shake as before for 10 min.ether layer into the second test-tube, combining it with the other 10.5 ml of ether. the aqueous layer. 10 min. the interface. To 2 ml of plasma or other body fluid contained in a 50-ml ground glass stoppered test-tube Stopptr firmly and shake for Transfer 10.5 ml of the upper ether layer into a second 50-ml (N.B., The pipette tip Add a further Transfer 15 ml of the upper, Discard Add 3 ml of hydrochloric acid, stopper tightly and shake as above for Remove and discard the upper ether layer using suction, taking care not to disturb Add a further 15 ml of ether to the aqueous layer followed by 0.5 ml of 1.0 N994 SHORT PAPERS Analyst, Vol. 105 sodium hydroxide solution and shake for 10 min as above.Transfer 12 ml of the ether layer into a 50-ml glass test-tube. Add a further 15 ml of ether to the aqueous layer and shake for 10 min as above. Remove 15 ml of the ether layer and combine it with the 12 ml of ether, Evaporate the ether to approximately 6 ml on a Dri-bath a t 50-56 "C under nitrogen and then transfer it into a 10-ml glass centrifuge tube. Wash the test-tube walls three times with 1 ml of ether, each time adding the washings to the centrifuge tube. Evaporate carefully to dryness on the Dri-bath as above, wash down the walls of the tube with 0.5 ml of ether and evaporate to dryness again. Add 100 pl of methanol to the residue and sonicate for approxi- mately 1 min whilst rotating and tilting the tube in the ultrasonic bath. Inject 5 p1 of the extract on to the HPLC column.With fresh plasma samples from sheep and cattle it was found that a shortened version of the above method could be used by evaporating the combined ether extracts from the first extraction, avoiding the need for a back-extraction. For rumeri and other gastro-intestinal samples the back-extraction was found to be necessary. The concentration of levamisole in the sample is calculated from calibration graphs pre- pared by adding known amounts (0.1-3.0 pg ml-l) of levamisole to blank plasma or gastro- intestinal fluid. The standard samples are extracted using the procedure described and the peak heights obtained for levamisole from the sample are compared with the calibration graph prepared from the standard samples. Typical chromatograms are shown in Fig.1. Using this method the concentration of levamisole in the sample is calculated as follows: By the standard method: Concentration in injected methanol solution 18.0 Concentration in sample = F By the short method: Concentration in injected methanol solution 18.6 Concentration in sample = I 1.1 I i C il ij JL G H J Time + Fig. 1. High-performance liquid chromatographic responses obtained after injection of 5 pl of: A, 5 ; B, 10; C , 15; ;and D, 20 p g ml-1 of levamisole in methanol; and 5 pl of the extracts obtained using the standard method from: E, blank plasma; F, plasma estimated to contain 0.42 p g ml-l; G, blank ruininal fluid; and H, ruminal fluid estimated to contain 0.36 pg ml-l.October, 1980 SHORT PAPERS Results 995 Recoveries of Levamisole from Plasma and Gastro-intestinal Fluids Aliquots of a solution of levamisole in methanol (20 pl) were added to samples of fresh plasma, rumen fluid and abomasal fluid to give concentrations of 1, 2, 5, 10 and 20 pg ml-I of levamisole.The plasma samples were extracted by the method outlined here and also by the short method (i.e., without back-extraction). The recoveries of levamisole from these samples after extraction were calculated from a calibration graph prepared from the peak heights of known standards of levamisole in methanol. The recoveries for plasma were 83% (73-90%, n = 12) by the standard method and 88% (81-98°/0, n = 30) by the short method, and for rumen fluid SOY0 (74-84%, n = 3) by the standard method. The limit of detection was between 0.02 and 0.05 pg ml-l, which is adequate for the con- centrations of levamisole found after normal doses (Table I). TABLE I DETERMINATION OF LEVAMISOLE IN PLASMA BY GC AND HPLC Mean concentrations of two levamisole determinations in plasma, as determined by the HPLC method and a gas-chromatographic method, after administration of levamisole (7.5 mg kg-l subcutaneously) t o two sheep.Levamisole concentration/pg ml-1 r--__-----A -- r----_h-- 1 v Sheep No. 1 Time/h HPLC GC HPLC Sheep No. 2 r---2-- 0 . . . . 0 0 0 0 1 . . . . 2.35 2.48 2.49 2.55 3 . . . . 1.02 1.18 1.56 1.69 6 . . . . 0.37 0.47 0.86 0.90 GE- Accuracy and Precision The accuracy and precision of the method for levamisole were determined by adding known amounts of levamisole to plasma. Samples of each known concentration were then assayed in triplicate by both the standard method and the short method (Table 11).I t was found that the low recoveries were due to extraction losses rather than to degradation of the levamisole. TABLE 11 LEVAMISOLE RECOVERIES Levamisole was added t o 2-ml plasma samples and assayed in triplicate by the standard procedure and by the short procedure. Allowance has been made in the levamisole measured for losses due t o not taking the total amount of extraction solvent a t each step. Amount of Levamisole Standard error Ratio of levamisole levamisole measured/ Mean & as percentage determined added/pg Method* Pg standard error/pg of the mean t o that added 0.4 A 0.34, 0.34, 0.32 0.33 i. 0.01 2.02 0.83 B 0.33, 0.30, 0.32 0.32 & 0.01 2.79 0.80 1.0 A 0.88, 0.84, 0.90 0.87 & 0.02 2.02 0.87 B 0.87, 0.80, 0.82 0.82 & 0.02 2.51 0.83 1.5 A 1.36, 1.50, 1.39 1.42 f 0.04 3.00 0.95 B 1.40, 1.28, 1.32 1.33 f 0.04 2.65 0.89 2.0 A 1.72, 1.68, 1.81 1.74 & 0.04 2.21 0.87 B 1.79, 1.67, 1.70 1.72 f 0.04 2.10 0.86 B 2.68, 2.66, 2.60 2.61 0.04 1.34 0.87 3.0 A 2.58, 2.76, 2.72 2.69 & 0.05 1.86 0.90 * A = Short procedure; B = standard procedure.996 SHORT PAPERS Analyst, Vol.105 Evaluation of the Method after Administration of Levamisole to Sheep and Com- parison with a Gas-chromatographic Method Levamisole* was administered subcutaneously at a dose of 7.5 mg; kg-l to two sheep and plasma samples were then collected at intervals. The samples w'ere nnalysed in duplicate by the standard method and also by an unpublished gas-chromatographic method. 1 The results obtained are shown in Table I. There was good agreement between the results obtained by the two methods. References 1. 2. 3. 4. 5. 6. 7. Forsyth, B. A,, J . S. Afr. Vet. Med. Assoc., 1966, 37, 403. Reid, J . F. S., Armour, J., Jennings, F. W., and Urquhart, G . M., Vet. Ilec., 1968, 83, 14. Lyons, E. T., Drudge, J . H., and Tolliver, S. C., Am. J . Vet Res., 1968, 29, 2157. Forsyth, B. A,, Aust. Vet. J., 1968, 44, 395. Ciordia, H., and Baird, D. M., Am. J . Vet. Res., 1969, 30, 1145. Holbrook, A,, and Scales, B., Anal. Biochem., 1967, 18, 46. Smith, J. E., Pasarela, R., and Wycroff, J. C., J. Assoc. O f f . Anal. Chem., 1976, 59, 954. Received March 28th, 1980 Accepted May lst, 1980 * Nilverm, Imperial Chemical Industries. t The gas-chromatographic analyses were kindly undertaken by Dr. A Featherstone of the Safety of Medicines Section, Imperial Chemical Industries.

ISSN:0003-2654    

DOI:10.1039/AN9800500993

出版商:RSC    

年代:1980

数据来源: RSC

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996 SHORT PAPERS Analyst, Vol. 105 Spectrophotometric Micro-determination of Silver( I ) and Iodide Ions Sudarsan Barua, B. S. Garg and R. P. Singh and lshwar Singh Depavtment of Chemistry, University of Delhi, Delhi-110007, India Department of Chemistry, Maharishi Dayanand Universaty, Rohtak-123001, India Keywords: S i l v e r ( I ) ; iodide; 4-(2-quinoZylazo)phenol This paper reports the analytical potential of 4-(2-quinolylazo)phenol (p-QAP), a new hetero- cyclic azo dye, as a sensitive chromogenic reagent in the spectrophotoinetric determination of silver(1). The silver(1) - (p-QAP) complex has also been used in the micro-determination of iodide ions. The principle involved is the ligand exchange reaction and the difference in absorbance between the silver(1) - (9-QAP) complex before and after the addition of iodide ions and the reagent blank is proportional to the concentration of iodide ions.The method is simple, rapid and the precision is high compared with some of the (other published methods.lJ Experimental Apparatus the spectra. Reagents p-QAP solution. 2-Hydrazinoquinoline (1.5 g, 0.01 mol) dissolved in the minimum volume of dilute hydrochloric acid or acetic acid was condensed with an ethanolic solution of p-benzoquinone (1.08 g, 0.01 mol). The resulting solution was neutralised with ammonia solution. The orange precipitate of p-QAP obtained was filtered, re-crystallised from ethanol and dried over phosphorus(V) oxide in a vacuum. The purity of the compound was checked by thin-layer chromatography and by elemental analysis (calculated values for C,,H,,N,O : A Unicam SP 600 spectrophotometer with matched 10-mm glass cells was used for recording A Beckman Expandomatic SS-2 pH meter was used for the pH measurements,October, 1980 SHORT PAPERS 997 C 72.28, H 4.42 and N 16.86%; the values found were C 72.00, H 4.48 and N 16.75%). A 5 x The solution is stable for several days.M solution of the reagent was prepared by dissolving 0.1245 g 1-1 in ethanol. 4-(2-Quinolylazo)phenol (p-QAP) Other reagents, standards and stock solutions. Standard solutions of silver(1) and iodide were prepared and standardised by conventional methods3; 0.05 M sodium tetraborate solution was prepared for adjusting the pH. All other chemicals used were of analytical-reagent grade. Recommended Procedure Determination of silver(I) To a suitable aliquot of sample containing 1.5-13.0 pg of silver(1) add 1.0 ml of 5 x lo-* M p-QAP solution followed by 1.0 ml of 0.05 M sodium tetraborate solution.Dilute to 10.0 ml with water and ethanol, giving a final ethanol concentration in the solution of 50%. Measure the absorbance of the solution a t 530 nm against a reagent blank. The amount of silver(1) in an unknown sample can be determined from a calibration graph prepared from known silver samples as described above. Determination of iodide ions using silver(I) - (p-QA P) M $-QAP solution followed by suitable aliquots of iodide solution containing up to 12.7 pg of iodide ions. Add 1.0 ml of 0.05 M sodium tetraborate solution, shake well and dilute to 10.0 ml with water giving a final ethanol concentration in the solution of 50%.Record the absorbance against a reagent blank. The difference in absorbance between the complex before and after the addition of iodide ions and the reagent blank is proportional to the concentration of iodide ions. To 1.0 ml of a 1 x M solution of silver(1) add 1.0 ml of 5 x Determination qf iodide ions by adding excess of silver(I) solution To an aliquot containing up to 15.0 pg of iodide add a known excess amount of silver(1). Allow to react for 1-2 min and then add 1.0 ml of 5 x M $-QAP solution followed by 1.0 ml of 0.05 M sodium tetraborate solution. Dilute to 10.0 ml with water and ethanol, again maintaining the ethanol concentration a t 50%, and record the absorbance against a reagent blank. The difference in absorbance between the complex before and after the addition of iodide ions and the reagent blank is proportional to the concentration of iodide ions, Results and Discussion Spectral Behaviour and Characteristics of the Silver (I) - (p-QAP) Complex An ethanolic solution of p-QAP forms a deep red coloured complex with silver(I), which has a maximum absorbance a t 530 nm in the pH range 8.1-11.2.The complex is stable in day- light. It decomposes when the ethanolic concentration is less than 30%; subsequent studies, therefore, were carried out in 50% ethanol solutions. Three moles of the reagent are required for full colour development. The composition of the complex, as determined by Job’s method of continuous variation and the molar ratio method, was found to be 1:2 (metal to ligand). Beer’s law is valid for up to 1.7 p.p.m.of silver. With the particular conditions adopted here 0.15-1.30 p.p.m. of silver can be determined accurately. The Sandell sensitivity of the colour system is 0.001 3 p g cm-2 of silver with a molar absorptivity, E , of 8.3 x lo4 1 mol-l cm-’ at 530 nm.998 SHORT PAPERS Analyst, V o l , 105 Studies in the Presence of Diverse Ions In the determination of 1.08 pg of silver(1) in solution, the results of the tolerance limits, in parts per million, of various ions in solution that caused a deviation smaller than 2% in absorbance are nitrite 800; sulphite 400; fluoride and tartrate 80; citrate and oxalate 60; chloride 20; bromide 15 ; lead( 11) 20; lanthanides(III), uranium(VI), cobalt (II), nickel( II), zinc(II), cadmium(I1) and iron(II1) 10.Iodide, sulphide, thiosulphate, thiocyanate, cyanide, EDTA, palladium(I1) and copper(I1) interfere. Determination of Iodide Ions The decomposition of the silver(1) - (9-QAP) complex in the presence of iodide ions was studied by taking varying amounts of silver(1) (0.15-1.30 pg ml-l). The amount of iodide ions determined was 0.09-1.5 pg ml-1 using the particular conditions adopted for the deter- mination of silver(1). The recovery results for iodide at ten known concentration levels (each repeated four times) of between 1.27 and 12.7 pg per 10 ml [1.08 pg ml-l of silver(I)] yielded coefficients of variation of less than 0.48y0. In each instance the difference between the measured and known concentration was less than 1.6%. The sensitivity of the method is 0.0015 pg cm-2 of iodide. Similar results were also obtained .when excess of silver(1) was allowed to react with iodide ions and unreacted silver(1) was determined following the recommended procedure. The effects of diverse ions upon the determination of 1.27 pg ml-l of iodide ions were also studied. Mercury(I1) interferes and other interferences were found to be of the same order as for the determination of silver(1). One of the authors (S.B.) is grateful to the University Grants Commission, New Delhi, India, for providing him with a Teacher Fellowship and Mr. Y. S. Varma for his helpful suggestions. References 1. 2. 3. Snell, F. D., “Photometric and Fluorometric Methods of Analysis, Metals, Part I,” John Wiley, New Marczenko, 2.. “Spectrophotometric Determination of Elements,” John Wiley, New York, 1976. Vogel, A. I., “A Text Book of Quantitative Inorganic Analysis,” Fourth Edition, Longmans, London, York, 1978. 1978. R.eceived Jafiuary 28th, 1980 Accepted May 29th, 1980

ISSN:0003-2654    

DOI:10.1039/AN9800500996

出版商:RSC    

年代:1980

数据来源: RSC

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998 SHORT PAPERS Analyst, V o l , 105 Rapid Gas-Liquid Chromatographic Determination of Cotinine in Biological Fluids C. Feyerabend and M. A, H. Russell Poisons Unit, New Cross Hospital, London, SE14 5ER Addiction Research Unit, Institute of Psychiatry, Maudsley Hospital, London, SE5 8A F Keywords: Cotinine determination; gas chromatography; plasma; saliva; urine Radioactive tracer techniques have been described for the measurement of cotinine in bio- logical fluids,l but they are cumbersome and inappropriate when large numbers of subjects are being investigated. It is preferable to use a gas - liquid chromatographic technique, especially when this can be achieved by simple modification of a routine method for nicotine measurement. We report here a rapid extraction procedure that allows the sensitive deter- mination of cotinine in biological samples without interference or contamination.October, 1980 SHORT PAPERS Experimental 999 Apparatus detector and a Model 3380A integrator was used, with an external time delay relay.A Hewlett-Packard, Model 5730A, chromatograph fitted with an alkali flame-ionisation Reagents All reagents were of analytical-reagent grade. Acetone. Dichloromethane. Pheniramine maleate. Hoechst Pharmaceuticals, Hounslow, Middlesex. Sodium hydroxide solutiora, 5 M. Gas - Liquid Chromatography A glass column (2.5 m x 2 mm i d . ) packed with 10% (m/m) Apiezon L and 10% potassium hydroxide on 80-100 mesh Chromosorb W was used. The temperatures of the oven, detector and injection port were 230, 300 and 250 "C, respectively. The retention times for cotinine and pheniramine free base were 2.66 and 3.17 min, respectively.The time delay relay device was used to overcome difficulties in the integration of peak areas, as described in detail elsewhere.2 Procedure To 1.0 ml of sample in a 12.5-ml centrifuge tube were added 2.0 ml of 5 M sodium hydroxide solution, 100 pl of an aqueous solution of phenirarnine rnaleate (2.2 pg ml-l) as internal standard and 3.0 ml of dichloromethane. The solution was vortex mixed for 2 rnin and then centrifuged for 5 min. Any emulsions were removed by discarding the aqueous layer, vortex mixing the centrifuge tube for a few seconds and centrifuging for 2 min. The organic layer was transferred into a second tube and evaporated to dryness under a stream of nitrogen a t room temperature.Acetone (50 pl) was added and the tube vortexed for 1 min and centri- fuged for 1 min. A 3-pl volume of the acetone solution was injected on to the chromato- graphic column. Calibration A calibration graph was constructed by adding cotinine and the internal standard to blank solutions of the sample type to be analysed to give concentrations of 25,50, 100,200,400,800 and 1000 ng ml-I. Although the calibration graph was linear from 0 to 1000 ng ml-1 and passed through the origin, care was taken to ensure that all cotinine concentrates were stored away from the analytical laboratory. Blanks Many of the problems of positive blanks associated with nicotine analysis3 do not occur in the cotinine method as this compound is present in cigarette smoke in much lower concentra- tions than nicotine.Reproducibility efficient of variation over this range was 1.8% (n = 10). The gas flow-rates were helium (carrier gas) 60, air 50 and hydrogen 3 ml min-l. These solutions were then carried through the extraction procedure. As a result, the risk of contamination is subsequently reduced. The reproducibility over a range of concentrations is shown in Table I. The average co- TABLE I REPRODUCIBILITY OF RESULTS OF TEN DETERMINATIONS AT VARIOUS COTININE CONCENTRATIONS Cotinine added/ng ml-l . . 25 50 100 200 400 600 800 1000 Cotinine found (mean)/ng ml-l 25.0 50.1 100.1 201.6 399.2 598.8 800.4 1000.3 Standard deviation/ng ml-1 . . 0.4 1.0 1.4 3.9 8.6 11.6 13.1 19.81000 SHORT PAPERS Analyst, Vol.105 Recovery The absolute recovery of cotinine (90%) was determined by injecting a mixture in acetone of cotinine (2000 pg 1-l) and pheniramine maleate (2000 +g 1-l). The peak-area ratio was compared with that obtained by injecting an extract of an aqueous solution of cotinine (1 ml; 100 pg 1-l) taken through the extraction procedure. The internal standard was introduced by reconstituting the cotinine extract in 50 p1 of acetone containing pheniramine maleate (2000 pg 1-l). (This procedure resulted in a final extract 20 times more concentrated than the original solution.) Results and Discussion A typical chromatogram of an extract from human plasma is shown in Fig. 1. The repro- ducible lower limit of determination of cotinine was 1 ng ml -l. No interference was found from the following common drugs: atropine, amphetamine, amitl-iptyline, chlorpheniramine, diphenhydramine, diethylpropion, fenfluramine, imipramine, lignocaine, methylamphetamine, nortriptyline, procaine, phentermine, sodium cromoglycate, salbutaniol and terbutaline. - 0 2 4 Timehin Fig.1. Gas chromato- gram of extract from human plasma: 1, cotinine and 2, pheniramine maleate. This method €or the determination of cotinine can be used in coiijunction with a previously reported extraction technique for n i c ~ t i n e . ~ . ~ Nicotine is extracted into diethyl ether and the sample is then re-extracted with dichloromethane to retrieve coiinine. Unlike Hengen and Her~gen,~ who reported no loss of cotinine during an extraction with diethyl ether, we found that a loss of cotinine occurred that was inversely proportional to the ratio of the volume of sample to that of the organic phase.Thus, with sample volumes of 3, 2 and 1 ml, the cotinine losses were 10,22 and 44%, respectively. It is therefore important to standardise the volume of sample if necessary, by the addition of tap water, and t o use the equivalent volume of plasma, saliva or urine standards to construct the calibration graph. In a preliminary experiment, a subject who had abstained from smoking for 10 days smoked a cigarette over a short period (3 min) and blood samples were withdrawn a t frequent intervals via an indwelling venous cannule. Samples of saliva and urine were also collected throughout the course of the experiment (Fig. 2). An increase in plasma cotiriine concentration occurred only 2 min after discarding the cigarette and the concentration rose steeply during the first hour and reached a plateau a t 4 h that persisted throughout the experiment. As expected, plasma nictoine concentrations reached a maximum within 2 min after smoking had ceased, fell sharply during the next 10-15 min and then more slowly over the remaining 6.5 h to approach base-line levels.Although cotinine (pK, 4.56) is essentially unionised in blood a t pH 7.4, the free base is poorly soluble in lipids and therefore its rate of distribution intoOctober, 1980 SHORT PAPERS 1001 60 50 40 30 20 10 0 0 1 0 2 0 3 0 4 0 5 0 6 0 2 3 4 5 6 7 Time/ rn i n Tirneih Fig. 2. Graph showing A, plasma nicotine; B, plasma cotinine and C, saliva cotinine, after smoking one 1.3-mg nicotine cigarette. Smoking period = 3 min.tissues may be slow. This would partially explain the prolonged existence of the compound in blood. Another contributing factor to this is the low rate of renal excretion of cotinine relative to nicotine (Fig. 3). This may account for the high concentrations of this metabolite (about 800 ng ml-l) often found in the plasma of habitual smokers. 0 1 2 3 4 5 6 7 Time/h Fig. 3. Urinary excretion of A , nicotine and B, cotinine over 7 h after smoking a 1.3-mg nicotine cigarette. The pII of the urine a t the different times is also shown. Nicotine is concentrated in saliva to give levels approximately 10 times higher than those measured in plasma,6 whereas salivary and plasma cotinine concentrations were essentially the same. We thank A. E. Bryant for technical assistance and the Medical Research Council for financial support. References 1. 2. 3. 4. 6. 6. Armitage, A. K., Dollery, C. T., George, C. F., Houseman, T. H., Lewis, P. J., and Turner, D. M., Feyerabend, C., and Russell, M. A. H., J . Pharm. Pharmacol., 1979, 31, 73. Feyerabend, C., and Russell, M. A. H., J . Pharm. Pharmacol., 1980, 32, 178. Hengen, N., and Hengen, M., Clin. Chem., 1978, 24, 50. Yamamoto, I., Adv. Pest Control. Res., 1966, 6, 231. Russell, hl. A. H., and Feyerabend, C., Drug Metab. Rev., 1978, 8, 29. Brit. Med. J . , 1975, 4, 313. Received March 19th, 1980 Accepted April 24th, 1980

ISSN:0003-2654    

DOI:10.1039/AN9800500998

出版商:RSC    

年代:1980

数据来源: RSC

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1002 Analyst, October, 1980 Com mu nica t ion Material f o r publication as a Communication must be on a n urgent matter and be of obvious scientijic importance. Rapidity of Publication i s enhanced i f diagrams are omitted, but tables and formulae can be included. Communications should not be simple claims for priority: this facility f o r rapid publication is intended f o r brief descriptions of work that has progressed to a stage at which i t i s likely to be valuable to workers faced with similar probl,sms. A fuller paper may be offered subsequently, i f justijied by later work. Manuscripts are not subjected to the usual examination by referees and inclusion of a Communication i s at the Editor's discretion. Limit of Detection in Analysis with Ion-selective Electrodes Keywords : Ion-selective electrodes ; potentiornetry ; limit of detection In an earlier paper1 approximations were used in deriving some of the equations [ ( 8 ) , (10) and (12)] expressing C,, the criterion of detection, and C,, the limit of detection, and these equations were restricted to electrodes whose responses were limited by the solubility products of isovalent ( 1 : 1) salts. In this paper, exact and general solutions are derived within the same treatment as before.Retaining the earlier notation1 [C = analytical determinand concentration, s = concentration of determinand dissolved from electrode, b, = reagent blank determinand, b , = ith interference effect, K = solubility product, uB = standard deviation of the blank (mv), Q = 2.330,, L = 4.650~1, the following derivations ensue for an electrode incorporating a salt A,B and responding to ion A.Response Not Limited by Solubility Product There is no change and equation (6) in the earlier paper' is exact and general in application, i.e., where b = b , + Cb6, C, = - l ) b Response Limited by Solubility Product Only In this instance b, = Xbd = 0 and the solubility product is given by (1) The e.m.f. can be expressed as follows: E = EO+ Klog [ K / ( ;.s>"]'" At C = 0, the blank e.m.f. is given by [ (;)"I l / ( Z + Y ) EB = EO + k log K At the criterion of detection, C = C,, s = s, and the e.m.f. is Hence,COMMUNICATION and 1003 Y/X V/(X+V) lo&/* = [ KlP( E) ] Sg'/" Substituting in equation (1) and solving for C, we obtain Equation (2) replaces equations (8), (14) and (16) in the earlier paper1 and also covers other stoicheiometries.The equation for the limit of detection, C,, is exactly analogous with L substituted for Q. Response Limited by Solubility Product and Interference As b, = 0, Zb, = b # 0 and the solubility product is still defined as in equation ( l ) , the e.m.f. can be expressed as follows: E = E O + k log { b + KllX/ (:.s)"") At C = 0, the blank e.m.f. is given by E , = E O + k l o g At the criterion of detection, C = C,, s = s, and the e.m.f. is E, = EO + k 1og{b + X1/X/(~*sQ)'/x} Now, Q = jE, - E,I, and hence Solving for s,, we obtain Hence, from equation (l), the criterion of detection is given by Equation (3) not only replaces equation (10) in the earlier paper1 but also extends the treat- The equation for the limit of detection, C,, is ment to electrodes based on non-isovalent salts. exactly analogous with L substituted for Q.1004 COMMUNICATION Analyst, VoZ.105 Response Limited by Solubility Product and Reagent :Blank Determinand In this case Xbd = 0 and b, # 0. The solubility product equation for a salt A,B, in an electrode responsive to ion A is . . (4) K = (C + b, + s)X [";..IU .. . . . . At C = 0, s = so and the e.m.f. of the blank is EB = Ea + k log { K / [ At the criterion of detection, C = C,, s = sQ and the e.m.f. is EQ = Eo + k log { K / [ Y;*S~]')"~ Hence, SQ = so 10-"Q/Uk From equation (4), the criterion of detection is K1/X For x = y = 1, equation (4) with C = 0 can be solved analytically to give so, which can be substi- tuted in equation ( 5 ) .For other stoicheiometries, so is best found by an iterative method, although for x = 2, y = 1 and x = 1, y = 2, so can be determined explicitly in terms of hyperbolic functions. Equations (2), (3) and (5) do not involve any approximations and are, therefore, more accurate than the earlier equations,l as shown in Table I. The newly calculated values agree more closely The equation for the limit of detection, C,, is exactly analogous to equation ( 5 ) . TABLE I CRITERIA AND LIMITS OF DETECTION FOR UNIVALENT ELECTRODES WITH uB = 1.0 mV Code* 7 B 106b,/mol 1-l . . . . .. 0 1O6Zb,/rnol 1-1 . . . . .. 0 10'2K . . .. . . . . 4 Equation used . . .. * . (2) 107CQ/mol 1-1- Graphical . . . . . . 3.63 This calculation . . . . 3.63 Previous calculation* .. . . 3.47 Graphical . . . . . . 7.41 This calculation . . . . 7.28 Previous calculation* . . . . 7.28 * See Table I11 in the earlier paper.' 107cL/mo1 1-1- C 0 1 1 (3) 3.43 3.49 4.28 6.76 6.81 8.23 D 1.5 0 1 (5) 2 29 2 33 199 4.79 4.79 4.03 v E 0 0 4 x 10-6 (3) 5.25 5.22 6.21 9.66 10.04 10.05October, 1980 COMMUNICATION 1005 with the graphical values, especially for electrodes C and D, for which the earlier treatment involved the greatest approximations. All of the discussion in the earlier paper is applicable to the more accurate equations developed here. It may also be noted that simple expressions exist for the limit and criterion of detection in the special cases where the e.m.f. can be measured with sufficient precision to allow limiting linear calibrations to be used.2 This work was carried out at the Central Electricity Research Laboratories and is published with the permission of the Central Electricity Generating Board. References 1. 2. Midgley, D., Analyst, 1979, 104, 248. Midgley, D., Analyst, 1980, 105, 417. Central Electricity Research Laboratories, Kelvin Avenue, Leatherhead, Surrey, KT22 7SE Received July 22nd, 1980 Derek Midgley

ISSN:0003-2654    

DOI:10.1039/AN9800501002

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

1006 Book Reviews Analyst, October, 1980 INTERNATIONAL COMMISSION FOR UNIFORM METHODS OF SUGAR ANALYSIS. REPORT OF THE The International Commission for Uniform Methods of Sugar Analysis. PROCEEDINGS OF THE SEVENTEENTH SESSION HELD IN MONTRE.4L, 4-9 JUNE, 1978. Pp. xxiv + 448. 1979. Price LZO. ISBN 0 905003 02 0. As the title states, this book reports the Proceedings of the 17th Session of ICUMSA held in Montreal from June 4th to 9th, 1978, under its President, Dr. A. Carruthers, and attended by about 120 delegates from 27 major sugar-producing countries. The format of the book is very similar to its predecessor, which reported on the 1974 Session. The subject matter remains substantially the same, being concerned with 29 topics, each of which covers a particular field of analytical interest to the sugar industry.The topics include specifications for laboratory apparatus and reagents, the determination of several physical properties and chemical parameters such as sucrose, reducing sugars and other saccharides, inorganic and organic non-sugars and dry substance. Additionally, microbiology, the deterioration, crystallisation and refining of sugars are discussed, and two new topics, method specification and ion-selective electrodes. For each subject the referee’s presentation, summarising work carried out since the last Session, and recommendations are fully reported, together with the ensuing discussion, the final recommendations adopted and appropriate references. The proceedings are reported clearly and concisely but, as would be expected, the subject matter is highly specific.For this reason the book is unlikely to appeal to those analysts having only a broad interest in sugar analysis. On the other hand, the book is a valuable manual for those actively engaged in this field and concerned with the latest views and developments. A. D. INCE GEL CHROMATOGRAPHY. THEORY, METHODOLOGY, APPLICATIONS. First English Edition. By TIBOR KREMMER and LLsz~6 BOROSS. Pp. 299. John Wley and Akadkmiai Kiad6. 1979. Price L16.50. ISBN 0 471 99548 7. This book is a revised version of the original Hungarian “GklkromatogrAfia” (Muszaki Konyvk- lad6, Budapest) translated into English by Mrs. M. GAbor. The text is presented in three parts: I, Fundamentals and Theory (by T. Kremmer); 11, Methods and ‘Techniques (by T.Kremmer); and 111, Applications (by L. Boross). Under headings I and I1 are covered the fundamental details of gels, the theory of the mechanisms of separation and the practical details covering selection and preparation of gels, selection and packing of columns and special techniques including thin- layer gel chromatography, gradient elution, zone precipitation and preparative procedures. Applications given in the third part of the volume include the fields of proteins, nucleic acids, synthetic polymers, carbohydrates, small molecule organic compounds and inorganic ions. From a practical viewpoint one of the most useful chapters in the book is that in which the selection, packing and use of columns are detailed, but a more detailed description of detection systems could have been included with advantage.Much of the book comprises a review of gel chromatography rather than a practical handbook for the student or user of the technique. I t thus tends to become more a work of reference and approximately 1 000 references are included. These are not numbered but are presented alphabetic- ally by author and in date order in a section at the end of the book, and hence they may take a little longer to identify. The reviewer feels that i t would have been helpful had more discussion on the qualitative and quantitative aspects, detection limits, etc., of the technique andL applications been included. Nevertheless, much useful information has been incorporated (not least the details given on bacteriostatic agents used for preserving the gels); the text is in clear English and the book seems well worth purchasing by both libraries and practical students of the technique.D. SIMPSONBOOK REVIEWS 1007 CARCINOGENS AKD RELATED SUBSTAKCES. ANALYTICAL CHEMISTRY FOR TOXICOLOGICAL RE- SEARCH. By MALCOLM c . BOWMAN. Pp. xii + 316. hiarcel Dekker. 1979. Price SwFr78. Recent changes in legislation concerning chemical substances have had a profound influence on the analytical aspects of toxicology. The legislation is still in a state of flux; however, this book from the National Centre for Toxicological Research (NCTR) gives a useful insight into the analytical thinking of the US Food and Drug Administration. While the book is directed specifically towards carcinogens, many of the principles described have a much wider application in analytical toxicology.In the book, the author stresses the importance of analytical measurements in the validity and safety of todays’ enormously expensive toxicology studies. “The control of a test substance begins when it enters the laboratory and ends only after its safe disposal.” In pursuit of this philosophy the book covers the importance of pre-study measurements to establish the identity, purity and stability of the test substance. Specific problems that can arise in this area are illustrated from the authors’ own experience a t NCTR. Contaminants in animal diet, bedding material or drinking water could influence the outcome of a toxicology study. A short section of the book is devoted to methods for the detection of trace amounts of likely impurities (i.e., afla- toxins, heavy metals and pesticides).By far the major portion of the book concentrates on the analysis of carcinogens that have been added to a variety of materials for the purpose of toxicological investigation. Here the object is to establish homogeneity, stability and approach to a nominal concentration. Aromatic amines are the subject of particular attention; however, oestrogens, specific mycotoxins, pesticides and a miscellaneous collection of other compounds are also covered in lesser detail. Methods for animal diet, drinking water, microbiological media, urine and blood are presented. There is a short section describing the experimental details of Salvtzonella typhimurium Test (Ames Test) of mutagenicity.While this is a useful description it seems a little out of place in an otherwise heavily analytical book. When working with carcinogens the safety of laboratory personnel is obviously of paramount importance. Many judgements on safety are based on analytical measurements and consequently methods are presented for the analysis of atmospheres and work surfaces and for the measurement of test substance in urine as an index of employee exposure. Contamination of the environment also receives consideration. I feel that many readers, like myself, will find the NCTR approach to removal of carcinogens from laboratory waste water excessively expensive and largely impracticable. I n more general terms I found this a useful and clearly written book, which could be of great value to anyone engaged in the analytical aspects of toxicology.It is obvious that much of what is presented is derived from the author’s own personal experience and has been carefully tailored to cover particular analytical problems. Although certain parts of the text are presented in the sort of detail one expects in a scientific paper, I feel that this does not detract from this extremely pertinent book. G. T. STEEL ISBN 0 8247 6885 X. ELECTROPHORESIS. A SURVEY OF TECHNIQUES AND APPLICATIONS. PART A: TECHNQUES. Edited by Z. DEYL, co-edited by F. &I. EVERAERTS, Z. PRUS~K and P. J . SVENDSEN. Journal of Chromatography Libvary, Volume 18. Pp. 390 + xv. Elsevier. 1979. Price $83; Df1.170. ISBN 0 444 41721 4 (Vol. 18); ISBX 0 444 41616 1 (Series).The Editor, aided by an eminent team of Co-editors, has collected together 17 chapters, each by a different author, to produce an impressive and worthwhile book. As the first volume of a two- part work, this deals with the principles, theory and instrumentation of modern electrophoretic methods; its companion, Part B, with a detailed survey of applications will come later. The book may be taken in two parts, namely, an introductory part covering the first four chapters and the remainder, Chapters 5-17, being devoted to the main business of a survey of the various electrophoretic techniques taken one by one. Taking the introductory part, Chapters 1-3, by J . Vacik, cover the essential theory, general classification of electrophoretic methods and the principles of evaluating results, and thereby form a coherent unit.Chapter 4, written by the Editor, takes a different stance and deals with the elimination of charge differences, such as by the formation of strongly negatively charged protein - detergent complexes with almost identical mobilities in free solution regardless of original charge.1008 BOOK REVIEWS Analyst, Vol. 105 This then provides a basis for relative molecular mass determination by electrophoresis on gel-type supports, where size and shape characteristics have their part to pla,y. The survey of techniques in Chapters 5-1 7 include zone electrophoresis (excepting gel-type and immunoelectrophoresis) (W. Ostrowski), gel-type techniques (Z. Hrkal), immunoelectrophoresis (P. J. Svendsen), moving boundary electrophoresis in narrow-bore tubes (F.M. Everaerts and J . L. Beckers), isoelectric focusing (N. Catsimpoolas), analytical isotachophoresis (J. Vacik and F. &I. Everaerts), continuous flow-through electrophoresis (Z. Prusik), continuous flow deviation electro- phoresis (the author does not regard “free-flow” as appropriate) (A. Kolin), preparative electro- phoresis in gel media (Z. Hrkal) and in columns (P. J. Svendsen), prepzrative isoelectric focusing (P. Blanicky), and preparative isotachophoresis by wide column (I?. J . Svendsen) and capillary methods (L. Arlinger). Consideration of each technique is based on a logical division into analytical and preparative aspects and, as can be seen from the chapter titles, every effort has bee.n made to avoid clashing.Nevertheless, discussions cannot always be complete without ref’erence to some of the other electrophoretic methods. Thus, for example, some reference is made .to SDS electrophoresis in Chapter 6 on gel-type techniques, although as mentioned above, the m.ain principles of this will have been discussed in Chapter 4. But then, this emphasises the essent.ia1 feature of this book as a practical work and i t is in Chapter 6 that the more mundane details of the recipe for an SDS - gel system are to be found. Thus, a contents list is generally followed by a concise introduction leading into the main business, frequently with practical details, and, where appro- priate, some illustrative applications in order to demonstrate the scope of the variant of the technique under consideration. The book, although very practical in its approach, gives due prominence to the underlying mathematical principles, supported by a range of clear line-diagrams. ThLere is also a good selection of illustrative diagrams and black and white pictures of apparatus arid separations, as well as copious lists of references at the end of chapters.It is a pity thoug’h that authors’ names in references are not collected in a separate index as the book might also be a good reference source. The book is enhanced by a list of the many symbols used in the text (pp. 379-384) and this is followed by an adequate subject index. For better consistency, res,ort might have been made to exercising some extra editorial prerogative in some quarters, such as the bringing of Chapter 12 into the ambit of SI units.The over-all conclusion must be, “ I like it,” and the book is bound to be well appreciated by other readers, particularly if they read the stimulating preface by Stelllan Hjerten for then they will not want to let go. Each chapter is systematically presented. J. D. R. THOMAS DIFFERENTIAL SCANNING CALORIMETRY. By J. L. MCNAUGHTON and c. T. MORTIMER. Reprinted from IRS: Physical Chewistry Series 2, 1975, Volume 10. Pp. ii + 44. Perkin-Elmer Corporation. 1979. This excellent booklet describes, in detail, the many applications of diifferential scanning calori- metry. It is a verbatim reprint of a chapter in “IRS: Physical Chemistry Series 2, 1975, Volume 10” and is published by Perkin-Elmer Corporation. The reader may thus infer, quite correctly, that it is heavily biased towards the equipment available from this company. Indeed, competitive apparatus receives but scant attention. On pp. 2 anti 3, reference is made to the IUPAC recommendations on nomenclature in thermal analysis (these were, in fact, originally made by the International Confederation for Thermal Analysis and subsequently accepted by IUPAC) and it is, therefore, a pity that throughout the booklet reference IS made to “thermogram” rather than the recommended “DSC curve.” The footnote on p. 4, which states that “the theory of DSC . . . is proprietory to the Perkin- Elmer Corporation,” is somewhat misleading. I n fact, “DSC 1” and “DSC 2” are Trade Marks of the Perkin-Elmer Corporation and anyone is free to use the term “differential scanning calori- metry” and the abbreviation “DSC.” The text is remarkably free from printing errors and indications arc’ that this booklet is available, free of charge, from the Perkin-Elmer Corporation. C. J. KEATTCH

ISSN:0003-2654    

DOI:10.1039/AN9800501006

出版商:RSC    

年代:1980

数据来源: RSC