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Spectrophotometric determination of ziram, ferbam and zineb with diphenylcarbazone
0039-9140/91 $3.00 + 0.00
Talanta, Vol. 38, No. 8, pp. 941-944, 1991 Printed in Great Britain. All rights reserved
Copyright 0 1991Pergamon Press plc
SPECTROPHOTOMETRIC DETERMINATION OF ZIRAM, FERBAM AND ZINEB WITH DIPHENYLCARBAZONE ASHOK KUMAR MALIK
and A. L.
J. RAO
Department of Chemistry, Punjabi University, Patiala 147002, India (Received 9 August 1990. Revised 8 February 1991. Accepted 20 February 1991) Summary-A procedure has been developed for the determination of ziram (zinc dimethyldithiocarbamate), ferbam (ferric dimethyldithiocarbamate) and zineb (zinc ethylenebisdithiocarbamate) after their decomposition and extraction of the diphenylcarbazone complexes of the zinc or iron into isobutyl methyl ketone. These complexes absorb strongly at 520 nm. The method is rapid, sensitive and selective and can be used for the determination of these dithiocarbamates in commercial and synthetic mixtures.
Dithiocarbamates have found a variety of applications in agriculture as pesticides and in the rubber industry as vulcanization accelerators and anti-oxidants. The toxicity of the dithiocarbamates is increased when they are in the form of heavy metal salts. The dithiocarbamates are generally determined on the basis of their decomposition by hot mineral acid to the amine and carbon disulphide. Most of the analytical methods for their determination are based on the Clarke method’ in which the dithiocarbamate is decomposed in acidic solution to give carbon disulphide, which is then absorbed in methanolic potassium hydroxide solution, and the potassium methyl xanthate so formed is titrated iodimetrically. Various modifications of this method are reported in the literature.2-‘3 Dithiocarbamates have also been determined in vegetables by high-pressure liquid chromatography,14 titrimetry” and extraction voltammetry. ‘*Ziram, ferbam and zineb have also been determined by converting these into copper”,‘* or molybdenum” complexes in acidic medium. The extraction of the molybdenum complexes is not rapid; for example, the molybdenum ethylenebisdithiocarbamate complex is extractable only after heating for 5 min. Here we present a new, simple, rapid, sensitive and selective method based on the determination of the zinc(H) and iron(II1) present in ziram, zineb and ferbam, respectively, by converting them into diphenylcarbazone complexes. EXPERIMENTAL
Equipment A digital ECIL pH-meter and an SP-20 Spectronic spectrophotometer were used.
Reagents All solvents and reagents were of analytical reagent grade. Ziram, ferbam and zineb solutions, I mgjml. Pure ziram and zineb were obtained from Wilson Laboratories, Bombay. Ferbam was prepared in the laboratory by the method given in the literature. 2o The purity of these samples was checked by elemental analysis and by determining their zinc and iron content by EDTA titrations, with Eriochrome Black T and Xylenol Orange, respectively, as indicators.” Stock solutions of ziram and zineb were prepared by dissolving 0.100 g in 100 ml of O.lM and 0.5M sodium hydroxide, respectively, and of ferbam by dissolving 0.100 g in 100 ml of acetonitrile. These solutions were standardized2’ and further diluted with sodium hydroxide solution or acetonitrile as required. Diphenylcarbazone solution, 3 mglml. Diphenylcarbazone (0.300 g) was dissolved in 100 ml of absolute ethanol. Pyridine solution, 50 mgjml. Pyridine (5.0 g) was dissolved in 100 ml of water. Buffer solution. Boric acid and potassium chloride solutions (0.2M, 100 ml of each) were mixed, adjusted to pH 9.0 with 0.244 sodium hydroxide, and diluted to 500 ml. Other solutions. Stock solutions for interference studies were prepared by dissolving suitable salts in water. Synthetic samples were prepared by mixing solutions of suitable salts to give the required composition. Zsobutyl methyl ketone. The purity of the isobutyl methyl ketone was checked spectrophotometricany before use. 941
ASHOKKUMARMALIK and A. L. J. RAO
942
Procedure
To aliquots of sample solutions containing 0.12-1.90 pg/ml ziram, 0.1 l-l .70 pg/ml zineb or 0.35-4.80 pg/ml ferbam add 2.0 ml of pyridine solution to ziram and zineb samples (but not to ferbam samples), and 3.0 ml of buffer solution, so that the pH after dilution to 25 ml is 9.0. Transfer into separating funnels, and add diphenylcarbazone solution (1 .O ml for ziram and zineb and 1.5 ml for ferbam) and 25 ml of isobutyl methyl ketone. Shake the mixtures for 5 min, separate the organic layers and measure the absorbances at 520 nm, against reagent blanks prepared under similar conditions. RESULTS AND DISCUSSION
The absorption spectra of the zinc(II)diphenylcarbazone-pyridine and iron(III)diphenylcarbazone complexes were recorded against reagent blanks. The complexes absorb strongly at 520 nm. The maximum absorbance was observed when the pH of the aqueous phase was 9.0-10.0 for ziram and zineb, and 9.0-l 1.0 for ferbam, and when 0.8-1.0 ml of 3 mg/ml diphenylcarbazone solution was used for ziram and zineb, and 1.0-l .5 ml for ferbam. Smaller amounts of diphenylcarbazone gave incomplete complex formation, but larger amounts did not increase the absorbance. Therefore use of 1.Oml for ziram and zineb and 1.5 ml for ferbam is recommended. The binary zinc-diphenylcarbazone complex is not completely extracted into isobutyl methyl ketone,** but it has been observed that the complex is completely extractable in one step into isobutyl methyl ketone in the presence of l-100 mg/ml pyridine in the aqueous phase; the extraction of the iron-diphenylcarbazone complex is unaffected by the presence or absence of pyridine. Various organic solvents were examined for the extraction of the complexes in the presence of pyridine. Chou et ~1.~~reported that pyridine enhances the extraction of zinc complexes through adduct formation. We have found that in the presence of pyridine the zinc-diphenyl-
carbazone complex is not extractable into diethyl ether and carbon disulphide but is extracted by benzene, n-butyl acetate, acetylacetone, n-amyl alcohol, n-amyl acetate, chloroform, carbon tetrachloride, toluene, isobutyl methyl ketone and ethyl acetate. Of these isobutyl methyl ketone and ethyl acetate were found to be the most effective. The extraction into isobutyl methyl ketone is slower than that into ethyl acetate, but because of the solubility of water in ethyl acetate isobutyl methyl ketone was selected for use. In isobutyl methyl ketone the complexes are stable for more than 8 hr. The Job, mole-ratio and logarithmic methods indicated the formation of the 1: 2 : 2 (M : L : Py) complex in the case of zinc and 1: 3 (M: L) complex in the case of iron(II1). Analytical characteristics
The calibration curves, for measurement at 520 nm, were linear over wide concentration ranges, given in Table 1 along with other performance characteristics. The limit of detection was calculated by the IUPAC recommended procedure.24 Interferences
Various foreign ions were examined for interference in the determination of 40 pg of ziram and zineb, and 100 ,ng of ferbam. Of the anions examined, the amounts (mg) shown in parentheses are tolerable: acetate (80), bromide (80), chloride (50), tartrate (50), thiosulphate (5); 100 mg of citrate, nitrate, oxalate, sulphate, sulphite or thiourea did not interfere, but metabisulphite and EDTA interfered strongly. Fluoride up to 100 mg is tolerable in the case of ziram and zineb, but only 2 mg in the determination of ferbam. Of the cations examined, Cu(I1) and Hg(I1) interfered but could be masked with 1.O ml of 50 mg/ml thiourea and potassium iodide solutions, respectively. Pb(II), Sn(IV), As(III), Ca(II), Cr(VI), Mo(V1) and Sb(II1) are tolerable up to 1.O mg and Hg(II), Bi(II1) and Mn(I1) up to 0.1 mg. Interference by free Zn(I1) or Fe(II1) is
Table I. Analytical characteristics of the determination of ziram, ferbam and zineb with diphenylcarbazone at 520 nm Characteristics
Ziram/zineb
Linear range, pg/ml Detection limit, pgglml Molar absorptivity, I.mole-‘.cm-’ Precision, RSD, %
0.12-1.9/0.1-1.7 0.08 8.36 x lo4 0.9
Ferbam 0.354.8 0.18 5.3 x IO4 1.0
Determination
943
of ziram, ferbam and zineb
by prior extraction of ziram, zineb or ferbam into chloroform, followed by evaporation of the organic phase to dryness. The mutual interference of ziram, zineb and ferbam was studied, along with the interference of some common pesticides such as thiram (tetramethylthiuram disulphide), nabam (disodium ethylenebisdithiocarbamate), maneb ethylenebisdithiocarbamate), (manganese vapam (sodium N-methyldithiocarbamate) and dibam (sodium dimethyldithiocarbamate). Pesticides containing no metal ion did not interfere in the determination of ziram, ferbam and zineb. Determination of ziram and zineb in the presence of ferbam and maneb was possible after masking with 2.0 ml of 50 mg/ml sodium fluoride and sodium citrate solutions, respectively. Ferbam in the presence of maneb was determined in the presence of 2.0 ml of 50 mg/ml sodium citrate solution. Ziram and zineb interfere in the determination of each other. avoided
Simultaneous determination of ziram andferbam, or zineb and ferbam
Ziram and ferbam or zineb and ferbam were taken in various proportions and dissolved in acetonitrile. Equal aliquots of the solution were analysed in the presence and absence of 2.0 ml of 50 mg/ml sodium fluoride solution. The difference in absorbance corresponded to the amount of ferbam.
Table 2. Recovery of dram, ferbam and zineb from grain Dithiocarbamate* Dithiocarbamate added Ziram Ferbam Zineb
.
Taken, /Q 40 50 40 50 20 40
Found, tig 38.9 49.0 38.0 49.5 19.0 39.0
Recovery, % 91.5 98 95 99 95 91.5
*Mean of three determinations. and the ferbam in acetonitrile, and analysed by the general procedure. Untreated samples were taken as reference. The results are given in Table 2. respectively,
Comparison
of sensitivity
The sensitivity of the present method is better than that of the methods of Lowen,” Cullen” and Chmie1,26 which are based on the determination of liberated CS2. It is also more sensitive than the direct methods reported by Rao et a1.‘9s28(5 and 2 pg/ml ziram and zineb), Rangaswamy et al. “Jo (1 pg/ml zineb and 0.8 pgg/ml ziram and ferbam) and Verma et aLz7 (0.6 fig/ml ferbam). By the present method it is possible to estimate 0.12, 0.35 and 0.11 pgg/ml ziram, ferbam and zineb, respectively. Acknawledgemenr-The authors thank the Bureau of Police Research and Development, New Delhi (India) for financial assistance to one of them (AKM).
Applications
The method is one of the most sensitive available for the determination of ziram, ferbam and zineb. Five dilutions of stock solutions prepared from “Ziram 27% S.C.” and “Dithane Z-78” were analysed, with pure samples of ziram and zineb as references, and in all cases the recoveries were between 98 and 100% with a relative standard deviation of 2-3%. Determination grain
of ziram, ferbam
and zineb
in
The procedure was applied to the determination of ziram, ferbam and zineb in grain. A known amount of ziram, ferbam and zineb was crushed with 20 g of grain and the mixture was shaken mechanically with 100 ml of chloroform for an hour. The mixtures were filtered and the residues were washed with three IO-ml portions of chloroform. The extracts were evaporated to 2.0 ml in a current of dry air at room temperature. The ziram and zineb residues were dissolved in 0. 1M and 0.5M sodium hvdroxide.
REFERENCES 1. D. G. Clarke, H. Baum, E. L. Stanley and W. E. Hester, Annl. Chem., 1951, 23, 1842. 2. T. Callan and N. J. Strafford, J. Sot. Chem. Ind., 1924, 43, 1T. 3. C. H. Hall, J. Assoc. 08 Agr. Chem., 1960, 43, 371. 4. J. Rosenthal, R. L. Carlsen and E. L. Stanley, ibid., 1953, 36, 1170. 5. H. Roth and W. Beck, Mikrochim. Acta, 1957, 844. 6. N. Yu. Frushevskaya in Tr. Vses. Soveshch. Issled. Ostatkov Pestiu. Profii, Zagryaz, Imi Prod. Pitan., Kormov Vnesh, Sredy, Znd, 1970, 0. M. Tamm (ed.), p. 276; Chem. Abstr., 1973, 79, 135377e. 7. W. R. Bontoyan, J. Assoc. Off. Agr. Chem., 1965, 48,
562. 8. C. Reinhard, Mitteilunsbl,
ADCh-Fachgruppe LebensGerichtl. Chem., 1971, 25, No. 1, 1. 9. B. W. Simpson, Pesric. Sci., 1971, 2, 127. mittelchem.
10. C. L. Hilton and J. E. Newell, Paper presented to Pittsburgh Conf. Anal. Chem. & Appl. Spectroscopy; abstract in Anal. Chem., 1953, 25, 530. 11. J. Piechocka, Rocz. Pansrw. Zakl. Hig., 1984, 35, 83. 12. W. K. Lowen, J. Assoc. 08 Agr. Chem., 1953,36,484. 13. S. Petrascu, Rev. Chim. (Bucharest), 1966, 17, 687. 14. K. H. Gustafsson and C. H. Falhgren, J. Agric. Food Chem., 1983, 31, 461.
944
ASHOK
KUMARMALIK and A. L. J. RAO
IS. B. C. Verma, H. S. Sidhu and R. K. Sood, Talanta, 1982, 29, 103. 16. N. A. Ulakhovich, E. P. Medyantseva, V. F. Frolova and 0. N. Romanova, Zh. Analit. Khim., 1983,%#, 1963. 17. J. R. Rangaswamy, P. Poomima and S. K. Majunder, J. Assoc. Off. Anal. Chem., 1971, S4, 1120. 18. I&m, ibid., 1970, 53, 1043. 19. A. L. J. Rao and N. Venna, Talanta, 1989, 36, 1041. 20. Monsanto Chemical Co., British Pat., 692063, 27 May 1953. 21. A. 1. Vogel, A Text Book of Quantitative Inorganic Analysis, 3rd Ed., Longmans, London, 1969.
22. H. Einaga and H. Ishii, Analyst, 1973, 98, 802. 23. F. C. Chou, Q. Fernando and H. Freiser. Anal. Chem., 1965, 37, 361. 24. G. L. Long and J. D. Winefordner, ibid., 1983, 55, 712A. 25. T. E. Cullen, ibid., 1964, 36, 221. 26. Z. Chmiel, Chem. Anal. (Warsaw), 1979, 24, 505. 27. B. C. Verma, R. K. Sood, A. Sood, S. Chauhan and D. K. Sharrna, Proc. Indian Natl. Sci. Acad. A. 1986, 52, 662. 28. A. L. J. Rao and N. Verma, J. Inst. Chemists (India), 1988, 60, 5.
Talanta, Vol. 38, No. 8, pp. 941-944, 1991 Printed in Great Britain. All rights reserved
Copyright 0 1991Pergamon Press plc
SPECTROPHOTOMETRIC DETERMINATION OF ZIRAM, FERBAM AND ZINEB WITH DIPHENYLCARBAZONE ASHOK KUMAR MALIK
and A. L.
J. RAO
Department of Chemistry, Punjabi University, Patiala 147002, India (Received 9 August 1990. Revised 8 February 1991. Accepted 20 February 1991) Summary-A procedure has been developed for the determination of ziram (zinc dimethyldithiocarbamate), ferbam (ferric dimethyldithiocarbamate) and zineb (zinc ethylenebisdithiocarbamate) after their decomposition and extraction of the diphenylcarbazone complexes of the zinc or iron into isobutyl methyl ketone. These complexes absorb strongly at 520 nm. The method is rapid, sensitive and selective and can be used for the determination of these dithiocarbamates in commercial and synthetic mixtures.
Dithiocarbamates have found a variety of applications in agriculture as pesticides and in the rubber industry as vulcanization accelerators and anti-oxidants. The toxicity of the dithiocarbamates is increased when they are in the form of heavy metal salts. The dithiocarbamates are generally determined on the basis of their decomposition by hot mineral acid to the amine and carbon disulphide. Most of the analytical methods for their determination are based on the Clarke method’ in which the dithiocarbamate is decomposed in acidic solution to give carbon disulphide, which is then absorbed in methanolic potassium hydroxide solution, and the potassium methyl xanthate so formed is titrated iodimetrically. Various modifications of this method are reported in the literature.2-‘3 Dithiocarbamates have also been determined in vegetables by high-pressure liquid chromatography,14 titrimetry” and extraction voltammetry. ‘*Ziram, ferbam and zineb have also been determined by converting these into copper”,‘* or molybdenum” complexes in acidic medium. The extraction of the molybdenum complexes is not rapid; for example, the molybdenum ethylenebisdithiocarbamate complex is extractable only after heating for 5 min. Here we present a new, simple, rapid, sensitive and selective method based on the determination of the zinc(H) and iron(II1) present in ziram, zineb and ferbam, respectively, by converting them into diphenylcarbazone complexes. EXPERIMENTAL
Equipment A digital ECIL pH-meter and an SP-20 Spectronic spectrophotometer were used.
Reagents All solvents and reagents were of analytical reagent grade. Ziram, ferbam and zineb solutions, I mgjml. Pure ziram and zineb were obtained from Wilson Laboratories, Bombay. Ferbam was prepared in the laboratory by the method given in the literature. 2o The purity of these samples was checked by elemental analysis and by determining their zinc and iron content by EDTA titrations, with Eriochrome Black T and Xylenol Orange, respectively, as indicators.” Stock solutions of ziram and zineb were prepared by dissolving 0.100 g in 100 ml of O.lM and 0.5M sodium hydroxide, respectively, and of ferbam by dissolving 0.100 g in 100 ml of acetonitrile. These solutions were standardized2’ and further diluted with sodium hydroxide solution or acetonitrile as required. Diphenylcarbazone solution, 3 mglml. Diphenylcarbazone (0.300 g) was dissolved in 100 ml of absolute ethanol. Pyridine solution, 50 mgjml. Pyridine (5.0 g) was dissolved in 100 ml of water. Buffer solution. Boric acid and potassium chloride solutions (0.2M, 100 ml of each) were mixed, adjusted to pH 9.0 with 0.244 sodium hydroxide, and diluted to 500 ml. Other solutions. Stock solutions for interference studies were prepared by dissolving suitable salts in water. Synthetic samples were prepared by mixing solutions of suitable salts to give the required composition. Zsobutyl methyl ketone. The purity of the isobutyl methyl ketone was checked spectrophotometricany before use. 941
ASHOKKUMARMALIK and A. L. J. RAO
942
Procedure
To aliquots of sample solutions containing 0.12-1.90 pg/ml ziram, 0.1 l-l .70 pg/ml zineb or 0.35-4.80 pg/ml ferbam add 2.0 ml of pyridine solution to ziram and zineb samples (but not to ferbam samples), and 3.0 ml of buffer solution, so that the pH after dilution to 25 ml is 9.0. Transfer into separating funnels, and add diphenylcarbazone solution (1 .O ml for ziram and zineb and 1.5 ml for ferbam) and 25 ml of isobutyl methyl ketone. Shake the mixtures for 5 min, separate the organic layers and measure the absorbances at 520 nm, against reagent blanks prepared under similar conditions. RESULTS AND DISCUSSION
The absorption spectra of the zinc(II)diphenylcarbazone-pyridine and iron(III)diphenylcarbazone complexes were recorded against reagent blanks. The complexes absorb strongly at 520 nm. The maximum absorbance was observed when the pH of the aqueous phase was 9.0-10.0 for ziram and zineb, and 9.0-l 1.0 for ferbam, and when 0.8-1.0 ml of 3 mg/ml diphenylcarbazone solution was used for ziram and zineb, and 1.0-l .5 ml for ferbam. Smaller amounts of diphenylcarbazone gave incomplete complex formation, but larger amounts did not increase the absorbance. Therefore use of 1.Oml for ziram and zineb and 1.5 ml for ferbam is recommended. The binary zinc-diphenylcarbazone complex is not completely extracted into isobutyl methyl ketone,** but it has been observed that the complex is completely extractable in one step into isobutyl methyl ketone in the presence of l-100 mg/ml pyridine in the aqueous phase; the extraction of the iron-diphenylcarbazone complex is unaffected by the presence or absence of pyridine. Various organic solvents were examined for the extraction of the complexes in the presence of pyridine. Chou et ~1.~~reported that pyridine enhances the extraction of zinc complexes through adduct formation. We have found that in the presence of pyridine the zinc-diphenyl-
carbazone complex is not extractable into diethyl ether and carbon disulphide but is extracted by benzene, n-butyl acetate, acetylacetone, n-amyl alcohol, n-amyl acetate, chloroform, carbon tetrachloride, toluene, isobutyl methyl ketone and ethyl acetate. Of these isobutyl methyl ketone and ethyl acetate were found to be the most effective. The extraction into isobutyl methyl ketone is slower than that into ethyl acetate, but because of the solubility of water in ethyl acetate isobutyl methyl ketone was selected for use. In isobutyl methyl ketone the complexes are stable for more than 8 hr. The Job, mole-ratio and logarithmic methods indicated the formation of the 1: 2 : 2 (M : L : Py) complex in the case of zinc and 1: 3 (M: L) complex in the case of iron(II1). Analytical characteristics
The calibration curves, for measurement at 520 nm, were linear over wide concentration ranges, given in Table 1 along with other performance characteristics. The limit of detection was calculated by the IUPAC recommended procedure.24 Interferences
Various foreign ions were examined for interference in the determination of 40 pg of ziram and zineb, and 100 ,ng of ferbam. Of the anions examined, the amounts (mg) shown in parentheses are tolerable: acetate (80), bromide (80), chloride (50), tartrate (50), thiosulphate (5); 100 mg of citrate, nitrate, oxalate, sulphate, sulphite or thiourea did not interfere, but metabisulphite and EDTA interfered strongly. Fluoride up to 100 mg is tolerable in the case of ziram and zineb, but only 2 mg in the determination of ferbam. Of the cations examined, Cu(I1) and Hg(I1) interfered but could be masked with 1.O ml of 50 mg/ml thiourea and potassium iodide solutions, respectively. Pb(II), Sn(IV), As(III), Ca(II), Cr(VI), Mo(V1) and Sb(II1) are tolerable up to 1.O mg and Hg(II), Bi(II1) and Mn(I1) up to 0.1 mg. Interference by free Zn(I1) or Fe(II1) is
Table I. Analytical characteristics of the determination of ziram, ferbam and zineb with diphenylcarbazone at 520 nm Characteristics
Ziram/zineb
Linear range, pg/ml Detection limit, pgglml Molar absorptivity, I.mole-‘.cm-’ Precision, RSD, %
0.12-1.9/0.1-1.7 0.08 8.36 x lo4 0.9
Ferbam 0.354.8 0.18 5.3 x IO4 1.0
Determination
943
of ziram, ferbam and zineb
by prior extraction of ziram, zineb or ferbam into chloroform, followed by evaporation of the organic phase to dryness. The mutual interference of ziram, zineb and ferbam was studied, along with the interference of some common pesticides such as thiram (tetramethylthiuram disulphide), nabam (disodium ethylenebisdithiocarbamate), maneb ethylenebisdithiocarbamate), (manganese vapam (sodium N-methyldithiocarbamate) and dibam (sodium dimethyldithiocarbamate). Pesticides containing no metal ion did not interfere in the determination of ziram, ferbam and zineb. Determination of ziram and zineb in the presence of ferbam and maneb was possible after masking with 2.0 ml of 50 mg/ml sodium fluoride and sodium citrate solutions, respectively. Ferbam in the presence of maneb was determined in the presence of 2.0 ml of 50 mg/ml sodium citrate solution. Ziram and zineb interfere in the determination of each other. avoided
Simultaneous determination of ziram andferbam, or zineb and ferbam
Ziram and ferbam or zineb and ferbam were taken in various proportions and dissolved in acetonitrile. Equal aliquots of the solution were analysed in the presence and absence of 2.0 ml of 50 mg/ml sodium fluoride solution. The difference in absorbance corresponded to the amount of ferbam.
Table 2. Recovery of dram, ferbam and zineb from grain Dithiocarbamate* Dithiocarbamate added Ziram Ferbam Zineb
.
Taken, /Q 40 50 40 50 20 40
Found, tig 38.9 49.0 38.0 49.5 19.0 39.0
Recovery, % 91.5 98 95 99 95 91.5
*Mean of three determinations. and the ferbam in acetonitrile, and analysed by the general procedure. Untreated samples were taken as reference. The results are given in Table 2. respectively,
Comparison
of sensitivity
The sensitivity of the present method is better than that of the methods of Lowen,” Cullen” and Chmie1,26 which are based on the determination of liberated CS2. It is also more sensitive than the direct methods reported by Rao et a1.‘9s28(5 and 2 pg/ml ziram and zineb), Rangaswamy et al. “Jo (1 pg/ml zineb and 0.8 pgg/ml ziram and ferbam) and Verma et aLz7 (0.6 fig/ml ferbam). By the present method it is possible to estimate 0.12, 0.35 and 0.11 pgg/ml ziram, ferbam and zineb, respectively. Acknawledgemenr-The authors thank the Bureau of Police Research and Development, New Delhi (India) for financial assistance to one of them (AKM).
Applications
The method is one of the most sensitive available for the determination of ziram, ferbam and zineb. Five dilutions of stock solutions prepared from “Ziram 27% S.C.” and “Dithane Z-78” were analysed, with pure samples of ziram and zineb as references, and in all cases the recoveries were between 98 and 100% with a relative standard deviation of 2-3%. Determination grain
of ziram, ferbam
and zineb
in
The procedure was applied to the determination of ziram, ferbam and zineb in grain. A known amount of ziram, ferbam and zineb was crushed with 20 g of grain and the mixture was shaken mechanically with 100 ml of chloroform for an hour. The mixtures were filtered and the residues were washed with three IO-ml portions of chloroform. The extracts were evaporated to 2.0 ml in a current of dry air at room temperature. The ziram and zineb residues were dissolved in 0. 1M and 0.5M sodium hvdroxide.
REFERENCES 1. D. G. Clarke, H. Baum, E. L. Stanley and W. E. Hester, Annl. Chem., 1951, 23, 1842. 2. T. Callan and N. J. Strafford, J. Sot. Chem. Ind., 1924, 43, 1T. 3. C. H. Hall, J. Assoc. 08 Agr. Chem., 1960, 43, 371. 4. J. Rosenthal, R. L. Carlsen and E. L. Stanley, ibid., 1953, 36, 1170. 5. H. Roth and W. Beck, Mikrochim. Acta, 1957, 844. 6. N. Yu. Frushevskaya in Tr. Vses. Soveshch. Issled. Ostatkov Pestiu. Profii, Zagryaz, Imi Prod. Pitan., Kormov Vnesh, Sredy, Znd, 1970, 0. M. Tamm (ed.), p. 276; Chem. Abstr., 1973, 79, 135377e. 7. W. R. Bontoyan, J. Assoc. Off. Agr. Chem., 1965, 48,
562. 8. C. Reinhard, Mitteilunsbl,
ADCh-Fachgruppe LebensGerichtl. Chem., 1971, 25, No. 1, 1. 9. B. W. Simpson, Pesric. Sci., 1971, 2, 127. mittelchem.
10. C. L. Hilton and J. E. Newell, Paper presented to Pittsburgh Conf. Anal. Chem. & Appl. Spectroscopy; abstract in Anal. Chem., 1953, 25, 530. 11. J. Piechocka, Rocz. Pansrw. Zakl. Hig., 1984, 35, 83. 12. W. K. Lowen, J. Assoc. 08 Agr. Chem., 1953,36,484. 13. S. Petrascu, Rev. Chim. (Bucharest), 1966, 17, 687. 14. K. H. Gustafsson and C. H. Falhgren, J. Agric. Food Chem., 1983, 31, 461.
944
ASHOK
KUMARMALIK and A. L. J. RAO
IS. B. C. Verma, H. S. Sidhu and R. K. Sood, Talanta, 1982, 29, 103. 16. N. A. Ulakhovich, E. P. Medyantseva, V. F. Frolova and 0. N. Romanova, Zh. Analit. Khim., 1983,%#, 1963. 17. J. R. Rangaswamy, P. Poomima and S. K. Majunder, J. Assoc. Off. Anal. Chem., 1971, S4, 1120. 18. I&m, ibid., 1970, 53, 1043. 19. A. L. J. Rao and N. Venna, Talanta, 1989, 36, 1041. 20. Monsanto Chemical Co., British Pat., 692063, 27 May 1953. 21. A. 1. Vogel, A Text Book of Quantitative Inorganic Analysis, 3rd Ed., Longmans, London, 1969.
22. H. Einaga and H. Ishii, Analyst, 1973, 98, 802. 23. F. C. Chou, Q. Fernando and H. Freiser. Anal. Chem., 1965, 37, 361. 24. G. L. Long and J. D. Winefordner, ibid., 1983, 55, 712A. 25. T. E. Cullen, ibid., 1964, 36, 221. 26. Z. Chmiel, Chem. Anal. (Warsaw), 1979, 24, 505. 27. B. C. Verma, R. K. Sood, A. Sood, S. Chauhan and D. K. Sharrna, Proc. Indian Natl. Sci. Acad. A. 1986, 52, 662. 28. A. L. J. Rao and N. Verma, J. Inst. Chemists (India), 1988, 60, 5.