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A high-performance thin-layer chromatographic method has been developed for determination of four carbamate residues in vegetables. The method uses two mobile phases on silica gel 60 F 254 GLP HPTLC layers, and detection at λ = 243 nm and 207 nm, the average wavelengths of maximum adsorption of pirimicarb and methomyl, and carbaryl and carbofuran, respectively. Recovery of 1.0–5.0 mg kg −1 of the four mixed carbamates from wax gourd and potatoes was 70.05–103.7%. The accuracy and precision of the method were confirmed by means of fortification experiments.

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Residues of three pyrethroids in spiked vegetables have been analyzed by HPTLC with two mobile phases in a twin-trough chamber and in horizontal chambers. The spots were detected at λ = 203 nm and the greatest detection sensitivity for the three pyrethroids was 10 ng. Recovery after fortification at 0.5–5.0 mg kg −1 was from 70.20 to 108.5%. The relative standard deviation was 1.59–27.94%.

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The phthalate esters (PAE) are ubiquitous in the environment because of the widespread use of plastic products. Reports of their harm to the environment and to human beings are increasing. This paper reports, for the first time as far as we are aware, use of HPTLC to separate and quantify PAE. The HPTLC assay enables separation of four PAE-dimethyl phthalate (DMP), diethyl phthalate (DEP), di- n -butyl phthalate (DBP), and bis-(2-ethylhexyl) phthalate (DEHP), priority pollutants listed by EPA- and qualitative and quantitative analysis of the compounds in water. The factors affecting the separation were investigated, including use of different stationary and mobile phases, different methods of development, humidity, and presaturation, or not, of the plate. The method was evaluated with water fortified at 5, 1, and 0.5 μg L −1 . It was then applied to detection of the compounds in water from Lake Chaohu. The assay was fully validated and shown to be sensitive (LOD ≤7 ng, LOQ 0.1 μg L −1 on HPTLC plates), accurate (recovery ≥80%), and precise (intra-day variation ≤8.7%, interday variation ≤6.7%). The results obtained by extraction using different solvents were compared. It was shown that dichloromethane was suitable for extraction of the four target substances from water.

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A simple, rapid, and sensitive high-performance thin-layer chromatographic method has been developed and validated for analysis of residues of imidacloprid, fenitrothion, and parathion in Chinese cabbage. The sample was extracted by sonication in an ultrasonic water bath with acetone-petroleum ether, 5:3 ( v / v ), and the extract was directly applied, as bands, to glass-backed silica gel 60F 254 HPTLC plates. The plates were developed with hexane-acetone, 7 + 3 ( v / v ), in an unsaturated glass twin-trough Camag chamber. Evaluation of the developed HPTLC plates was performed densitometrically with a Camag TLC Scanner 3 controlled by an external PC running Wincats software (Version 1.1.2). The results indicated that the detection limits of imidacloprid ( R F = 0.10), fenitrothion ( R F = 0.59), and parathion ( R F = 0.70) were 5.0 × 10 −9 g, 2.0 × 10 −8 g, 1.0 × 10 −8 g, respectively. Recoveries of the pesticides from Chinese cabbage by use of this analytical method were 80.04–85.22%, and RSD were 4.18–13.15%. The precision and accuracy of the method were generally fit for analysis of pesticide residues in Chinese cabbage.

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Octachlorodipropyl ether (OCDPE) is a chloroalkyl ether widely used as an insecticide synergist, which was considered as a widespread persistent pollutant. Photodegradation kinetics of OCDPE in selected organic solvents was studied using the high-performance thin-layer chromatography (HPTLC) method in this paper. The results showed that photochemical reaction of OCDPE in organic solvents such as n-hexane, methanol, acetonitrile, and acetone under the irradiation of ultraviolet light could well be described by the first-order kinetic equation. The photodegradation rate constants of OCDPE in methanol, acetone, acetonitrile, and n-hexane were 0.3310, 0.2382, 0.0287, and 0.0276 h−1, and the corresponding half-lives were 2.09, 2.91, 24.1, and 25.1 h, respectively. Photodegradation kinetics of OCDPE under sunlight was slower than UV light, the half-lives of which were 8.87 and 2.09 h, respectively. The main photodegradation products of OCDPE in acetone and methanol under UV light were detected by HPTLC, which included product 01 (R F = 0.19) and product 02 (R F = 0.82). Identification of the main photodegradation products of OCDPE requires further studies.

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In this work we have studied the separation of a mixture of the sulfonylurea herbicides (metsulfuron-methyl, chlorsulfuron, bensulfuron-methyl, tribenuron, chlorimuron-ethyl) by HPTLC on silica gel F 254 plates, with two different mobile phases. We also studied the effect of humidity on the separation. Bensulfuron-methyl added to tapwater at levels of 5, 10, and 20 µg kg −1 were determined after extraction by LC 18 SPE. Detection limits of the method are given.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Haiqun Cao, Yongde Yue, Rimao Hua, Feng Tang, Yanhong Shi, Xiangwei Wu, Rong Zhang, and Mengxing Xie

A simple, rapid, and sensitive high-performance thin-layer chromatographic method for analysis of octachlorodipropyl ether (OCDPE) in insecticide formulations has been established and validated. Known amounts of analytical grade OCDPE and its emulsifiable concentrate (EC) or wettable powder (WP) formulations were characterized by HPTLC on silica gel with toluene-acetic acidwater 20:20:1 ( v/v ) as mobile phase; detection was by spraying with silver nitrate-2 m alcoholic potassium hydroxide as chromogenic reagent and exposure to UV light. The plates were evaluated densitometrically at 399 nm. The results indicated that the calibration plot for OCDPE was logarithmic in the range 0.2–5.0 μg per band, and the correlation coefficient for the calibration equation in this range was 0.99. Recoveries from laboratory-prepared test EC and WP formulations using this method were 98.5–103.9% and 95.3–104.3%, respectively, and the respective RSDs were 3.39–4.89% and 2.92–5.33%. The accuracy and precision of the method were suitable for analysis of OCDPE in pesticide formulations.

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