Microdetermination of parathions by thermo- and ultra-violet decomposition products.

By means of the thin layer chromatography (TLC) a study was carried out on the decomposition of methyl parathion, ethyl parathion and sumithion when exposed to heat or ultra-violet irradiation. The results are briefly summarized as follows. 1. Parathions, when exposed to heat, form hydrolysates and such 0-analog as paraoxon as well as S-alky1 isomers. 2. When parathions are exposed to ultra-violet rays at 365 mμ and 254 mμ, the rate of decomposition is extremely slow. For example, when exposed to such rays in Petri dish for 5 hours, only a small amount of Salkyl isomer is formed. 3. After heating parathions in a small test tube and conducting TLC, when each 0-analog and S-alkyl isomer above mentioned is confirmed, it is poible to identify a minute amount of each parathion by this method, and thus this method is feasible to apply to practical poison examination as a rapid and simple qualitative examination method. ∗PMID: 4239572 [PubMed indexed for MEDLINE] Copyright c ©OKAYAMA UNIVERSITY MEDICAL SCHOOL Acta Med. Okayama 22, 281-291 (1968) MICRODETERMINATION OF PARATHIONS BY THERMO. AND ULTRA-VIOLET DECOMPOSITION PRODUCTS Yositaka DOl, Kyoichi HABA, Michiko IMAI, Setsuko HAYAKAW A and Sadakazu SAITO Department of Legal Medicine, Okayama University Medical School Okayama (Director: Prof. Y. Mikami) Recei.ved for publication, November 2, 1968 In order to make microdetermination and to detect the parathions with ease, parathions isomerization produced by thermoand ultra-violet decomposition were studied. Parathions were decomposed by heating or ultra-violet irradiation, and then the decomposition products were separated by the thin-layer chromatography (TLC), extracted from the thin layer, and these extracts were further analyzed by several steps such as the colorimetric method, TLC, gas-chromatography (GC), infrared analy. sis (IR) and ultra-violet absorption analysis (UV) to identify individual product. The present communication deals briefly with the results obtained. MATERIALS AND METHODS As the test materials methyl parathion, ethyl parathion and sumithion of over 9596 purity were made into acetone solution. To get pure pesticides each of these solutions is lined on the thin layer plate, and developed by n-hexaneacetone (4: 1, v lv, G. R.) and spot parts of pesticides on the Silicagel G (SG, Merk) layer were picked up, extracted into n-hexane.acetone (l : 1, vlv, G. R.). Each pesticide is confirmed to contain no contaminant by the TLO with nhexane-acetone (4 : 1, vlv, G. R.), and serves for the experiments. As the preparation of thin layer plates SG is coated in the thickness 0.25 mm on a 20 X 20 cm glass plate using an applicator of Taya Roshi 00. Japan. Dry the thin plates 5 hours at room temperature, and activate them in an oven at 100-115°0 for 60 minutes. Keep them in a desiccator to serve for the need. About 10 mg each of the above sample in a Petri dish is decomposed by heating on a sand bath to 150°0 with thermoelectric thermometer for 5 hours or by ultra-violet rays exposure with either at 365 m,u (without filter) or at 254 m,tt of UV.lam p for 5 hours. Then each decomposed pesticide is dissolved in a minute acetone solution and again lined on the SG layer and developed with solution of n-hexanechloroform.methano1 (7: 2: 0.5, v/v, G. R.) or toluene-dioxane (7: 1, v/v, G. 281 1 Doi et al.: Microdetermination of parathions by thermoand ultra-violet Produced by The Berkeley Electronic Press, 1968 282 Y. 001, K. HABA, M.IMAI, S. HAYAKAWA and S. SAITO R.). Spot parts of SG layer are picked up, and extracted into n.hexane-acetone (1 : 1, vlv, G. R.) solution. The oily decomposed substances thus obtained are examined with coloration by 20 % methanolic solution of potassium hydroxide, 0.5% cyclohexane solution of 2,6-dibromoquinonechlorimide (Gibbs reagent) and Diazo reagent. Next, they are analyzed with Shimadzu Model GC-IC gas chromato. graph equipped with a hydrogen flame detector (Shimadzu Model FID.1B) and a 180 cm x 0.3 cm stainless steel column containing 5 % SE.30 on Schimalite. Operating conditions are: column temperature, 195°C, detector temperature 215°C. Carrier gas helium 30 ml/min, sensitivity 10-2, range 0.8 V., sample 1/.l1. They are subjected to further analysis with infrared analysis (IR) using Hitachi ModelE PI.G2 (resolution, 2 cm-I/IOOO em-I, gain 3, scan speed Fast-2, sample KBr tablet) and with ultra-violet absorption analysis (UV) using Shimadzu Model QB.60. As for the detection of a minute quantity of parathions each pesticide is decomposed on the SG layer on which 10 to 20l-lg of the sample in acetone solution is spotted. Thin layer plates are heated variously in an oven in the range of 110-150°C for 30-60 min or exposed to ultra-violet rays of 365 m/.l or 254 m,u at the distance of about 20 em for about 2 hours and developed with n-hexane-chloroform-methanol (7: 2: 0.5, vlv, G. R.), and for the identi. fication of spots 20 % methanolic solution of potassium hydroxide as the spray reagent is used. Moreover, by exposing to ultra-violet lamp at 365 m/.l, spotted sample is heated to about 60°C. To establish most suitable conditions of the thermodecomposition, about 10-20/.lg sample is put in a test tube, 7-8 em in inside diameter and 1012 em in length, and heated with the heat apparatus as shown in Fig. 1, and changing the heat temperature and heating time. Fig. 1 Apparatus of Themodecomposition of Thiophosphates RESULTS 1. Thin layer chromatograj)h)! of thermoand photo. decomposition of parathions: In decomposing each sample by heating in a Petri dish to 150°C for 5 hours, there appear 3 spots besides parathions in the TLC as shown in Fig. 2 and Table 1. The lowest spot (shaded spots of low part in Fig. 2) is 2 Acta Medica Okayama, Vol. 22 [1968], Iss. 5, Art. 6 http://escholarship.lib.okayama-u.ac.jp/amo/vol22/iss5/6 Microdermination of Parathions Solvent TOI~.~e :: D:o~ane ~exane:CHC~: MeOH n+l,xal'e :: AClet~ne 7 :2 : 0.5-1 @j """' .z;, .... ~ ~ 0 <%> ~ a> @ ®i ,e e f)' 4P ~ ~ • 0 lI) c:o ell ID .. Sample Mt" ~... SM Mel MP EP SM Mel MP EP 8M Ma Fig. 2 Spots of Thermodecomposition Products of Thiophosphate (Heated at 150°C for 5 hrs) Table 1 Rf-Values of 4 Thiophosphates and their Decomposition Products on SG Layers 283 Solvents used Toluene: Dioxane (7 : 1) n-Hexane: CHCla: \1eOH (7: 1 :0.5) n-Hexane: Acetone (4 : 1) M. Parathion 8 7 96 6 5 Ml 3 0 4 8 1 9 M2 5 1 6 5 2 7 E. Parathion I 9 1 I 9 8 9 0 E 1 4 7 7 6 3 0 E 2 I 6 0 I 8 8 4 1 Sumithion 8 9 9 6 7 3 S 1 3 7 6 0 2 2 S 2 5 3 7 4 3 5 Marathion I 7 8 9 7 6 9 Mal 4 4 6 5 3 0 Ma2 I 7 1 9 4 5 7 Ma3 8 9 9 8 7 9 p-Nitrophenol 3 0 1 a 2 5 identified as 3-nitrophenol (NP) or 4-methyl-3-nitrophenol (MNP) from the results of colorimetric examination and infrared analysis and its upper spots are designated in the case of methyl parathion (MP) as M ll M2 with ethyl parathion (EP) as Ell E2 and with Sumithion (SM) as Sll S2' and these were further studied. For the sake of convenience M 1, £1 and SI are grouped as group 1, M2, E2and SJ as group 2. Even in the exposure to ultra-violet rays of either at 365 mp. and 254 mp., the decomposition of parathion occurs only slightly (Fig. 3). Moreover in the TLC only spot I 3 Doi et al.: Microdetermination of parathions by thermoand ultra-violet Produced by The Berkeley Electronic Press, 1968 284 Y.OOl, K. HABA, M.IMAI, S. HAYAKAWA and S. SAITO Solvent n-Hexone: CHC~: MeOH (7: 2 :0.5 n·Hexone: Acetone(4'1) 365 254 365 W'roy --"'I'I--::G>=-....,,-=-..... .--+---:_~--.--_=--+--------