[Agr. Biol. Chem., Vol. 29, No. I, p. 56•`60, 1965]

Gas-Liquid Chromatography of Organophosphorus Pesticides*

By Jun KANAZAWA, Hiroshi KUBO** and Rokuro SATO**

Agricultural Chemicals Inspection Station, Ministry of Agriculture and Forestry,

Kodaira, Tokyo

Received July 29, 1964

A method for separation and identification of mixtures of organophosphorus pesticides

by gas-liquid chromatography with the thermal conductivity detector is described. By the combination of 6 operating conditions with three columns containing high vacuum silicone

grease, silicone compound DC-11 and fluorosilicone FS-1265, mixtures of up to 19 organo phosphorus pesticides can be mutually separated. This technique should be very useful for quality control of pesticide formulation, residue analysis and legal medicine.

Nowadays in our country a many kinds of results on the selection of stationary phase organophosphorus pesticide have been used for liquid and column conditions for separation of the control of noxious insects of crops and 19 organophosphorus pesticides by means of hygiene. Many of them have generally such the gas-liquid chromatography. high poisonous character for the mammals EXPERIMENTAL that from view-points of standard manage Apparatus. ment of formulations, toxicology and legal The apparatus used in the present investigation medicine, a simple rapid method is needed was a Shimadzu Model GC-2B gas chromatograph, for the qualitative and quantitative identifica equipped with a thermal conductivity type of detector tions of these pesticides in mixtures, in com and a 2-mV. recorder at full scale. The column used mercial preparations and treated foodstuffs. was a stainless steel spiral tubing of 1m. long with In recent years the gas chromatograph has 4mm. internal diameter. become increasingly popular as an analytical Column Packings. instrument. Gas chromatography has been al In all of this work 32- to 48-mesh Celite 545 was ready utilized for separation, identification.1•`6) used as supporting medium. Three stationary phases However, little work has been carried out on were used as follows: 1) 5% high vacuum silicone the mutually qualitative analysis of a number grease (HVSG); 2) 5% silicone compound (DC-11); 3) 5% fluorosilicone (FS-1265). These all are products of these pesticides, except the report by of Dow-Corning. Ethylacetate for HVSG and FS-1265 Giuffrida.6) , chloroform for DC-11 were used as the coating solvents In this paper the authors wish to report the to Celite 545. * Gas Chromatography of Agricultural Chemicals . Part Samples.

XVI. ** Present address: Tokyo University of Agriculture and Organophosphorus pesticides tested were Bis-0,0-di Technology, Fuchu, Tokyo. ethyl-phosphoric anhydride (TEPP) , 0,0-dimethyl-2,2- 1) D. M. Coulson, L. A. Cavanagh and L Stuart, J. Agr . dichlorovinyl phosphate (DDVP), 0,0-dimethyl 0-(2- Food Chem., 7, 250 (1959). 2) J. Kanazawa and R. Sato, Bunseki Kagaku, 11, 122 ethylthio)ethyl phosphorodithioate (Thiono methyl (1962). demeton), 0,0-diethyl S-ethylthiomethyl phosphoro 3) D. L. Petitjean and C. D. Lantz, J. Gas Chromatog., 1(2), 23 (1963). dithioate (Thimet), 0,0-diethyl 0-(2-ethylthio)ethyl 4) T. Nishimoto and M. Ueda, Shokuhin Eiseigaku Zasshi , 4 phosphorodithioate (Thiono dimeton) Octamethyl- 192 (1963). 5) R. C. Nelson, J. Assoc. Offic. Agr. Chem. 47, 289 (1964). pyrophosphoramide (Schradan), 0,0-diethyl S-(2-ethyl 6) L. Giuffrida, ibid., 47, 293 (1964). thio)ethyl phosphorodithioate (Di-syston), 0,0-diethyl Gas-Liquid Chromatography of Organophosphorus Pesticides 57

0-(2-isopropyl-6-methyl-4-pyrimidiyl phosphorothioate 0-p-nitrophenyl phosphorothioate (parathion), 0,0,0'0'- (diazinon), 0,0-diethyl 0-2,4-dichlorophenyl phosphoro tetraethyl S,S'-methylene bisphosphorodithioate dithioate (VC-13), 0,0-dimethyl S-(N-methylcarbamoyl- (ethion), 0,0-diethyl S-(p-chlorophenylthio)methyl methyl) phosphorodithioate (dimethoate), 0,0-dimethyl phosphorodithioate (Trithion), 0-ethyl 0 p-nitrophenyl 0-p-nitrophenyl phosphorothioate (methyl (parathion) , 0 phenylphosphonothioate (EPN), 0,0-diethyl S-(2,5-di ,0-dimethyl 0-3-methyl-4-nitrophenyl phosphorothio chlorophenylthio)methyl phosphorodithioate (Phenkap ate (Sumithion), 0,0-dimethyl 0-(4-methylthio-m-tolyl) ton). In these diazinon, dimethoate and methyl para phosphorothioate (Baycid), 0,0-dimethyl S-(1,2-dicarbe- thion used were chemical pure material, the other thoxyethyl) phosphorodithioate (malathion), 0,0-diethyl pesticides were technical grades. Twenty-five weight per cent toluene solution of the parent compounds TABLE I. OPERATING CONDITIONS was used. But only dimethoate was used in acetone solution owing to poor solubility in toluene. Operating Conditions. Helium was used for the carrier gas. The detector filament current was adjusted to 200 mA at the

TABLE II. RETENTION TIMES OF ORGANO PHOSPHORUS PESTICIDES

FIG. 1. Gas Chromatogram of Mixtures of Organophosphorus Pesticides. 58 Jun KANAZAWA, Hiroshi KUBO and Rokuro SATO operating column temperature. The sample size was In the three column packings, high vacuum 1 to 2ƒÊl at 2 to 4mV, full scale span of the recorder, silicone grease column gave the sharpest and and the chart speed was 1cm per minute. The the most symmetrical peaks, and peak resolu operating conditions used in this investigation were tion of the each pesticides was good at column shown in Table I. temperature 165•Ž. Under this operating condition (I), the organophosphorus pesticides RESULTS AND DISCUSSION eluted in the following order : TEPP and

The retention times and their relative values DDVP (Group A), Thiono methyl demeton

(methyl parathion or ethion as the unity) of (B), Thimet (C), Thiono demeton (D), Di the organophosphorus pesticides tested were syston, Schradan and diazinon (Group E), VC- shown in the Table II. 13, dimethoate and methyl parathion (Group

FIG. 2. Gas Chromatograms of Mixtures of Organophosphorus Pesticides , Gas-Liquid Chromatogray of Organophosphorus Pesticides 59

F), Sumithion (G), Baycid, malathion and a column with fluorosilicone FS-1265 as the parathion (Group H), (Fig. 1). Accordingly stationary phase at column temperature 170•Ž at least 8 sorts of the those organophosphorus (Condition III), these mixtures can be satis pesticides can be separated completely under factorily separated (Fig. 2). this operating condition. However, the The vapor pressures of ethion, Trithion, operating condition (1) does not mutually EPN and Phenkapton are so relatively low separate compounds within group, for ex that the column temperature must be raised ample, VC-13, dimethoate and methyl to 195•Ž. In the operating condition (IV), parathion (Group F) or Baycid, malathion the column with high vacuum silicone grease and parathion (Group H), whereas by using as the stationary phase does not separate EPN

FIG. 3. Gas Chromatograms of Mixtures of Organophosphorus Pesticides. 60 Jun KANAZAWA, Hiroshi KUBO and Rokuro SATO

and Phenkapton, but under the operating decomposition of some organophosphorus condition (VI) with fluorosilicone FS-1265, pesticides. This finding agrees with the indi these can be separated (Fig. 3). cation presented by Crosby and Laws.7) Though the column with silicone compound Thus by the combination of two or three DC-11 has almost the same separating ability columns packed with silicone of different to high vacuum silicone grease column, the property, a large number of organophosphorus retention order is changed a little, especially pesticides were qualitatively analysed. This the retention time of dimethoate is considera work would be applicable to the composition bly shorten. analysis of formulated products, to the residue The column containing silicone Gum SE-30 analysis, and to the legal medicine by the as the stationary phase was also suitable for combination of extraction and cleanup the present objects, which gave approximately method.8,9) the same relative retention times comparable to those obtained with silicone compound DC- Acknowledgement. The authors wish to 11. Polyethylene glycol 6000 was unsatisfac thank Sumitomo Chem. Co., Nihon Kayaku tory as the stationary phase for this work, Co. and Nihon Tokushu Noyaku Co., for because this column gave generally tailing kind supply of technical products of organo peaks probably owing to its affinity with phosphorus pesticides. organophosphorus pesticides. 7) N. T. Crosby and E. Q. Laws, Analyst, 89, 319 (1964). Stainless steel must be used as the column 8) R. Moddes and J. W. Cook, j. Assoc. Offic. Agr. Chem., 42, 208 (1959). material. The copper column caused thermal 9) D. E. Coffin and W. P. Mckinley, ibid, 46, 223 (1963).