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A simple, rapid, and sensitive high-performance thin layer chromatographic method for analysis of the residues of tricyclazole, thiram, and folpet in tomatoes has been established and validated. The sample was extracted by mechanical vibration at room temperature with acetone-dichloromethane 1:1 ( 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 6+4 ( v/v ) in an unsaturated glass twin-trough chamber. Evaluation of the developed HPTLC plates was performed densitometrically. The results indicated that the detection limits of tricyclazole ( R F = 0.26), thiram ( R F = 0.65), and folpet ( R F = 0.77) were 1.2 × 10 −8 , 3.0 × 10 −8 , 4.0 × 10 −8 g, respectively. Recoveries of the pesticides from tomatoes with this analytical method were 67.66–98.02%, and RSD were 0.13–22.06%. The precision and accuracy of this method were generally fit for analysis of pesticide residues in tomatoes.

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HPTLC and HPLC methods have been established for separation and quantitative determination of puerarin, 3′-methoxypuerarin, daidzin, and daidzein, the main isoflavonoid components of several kudzu samples. HPTLC was accomplished within 70 mm migration distance and approx. 20 min migration time on silica gel F 254 HPTLC plates with chloroform-methanol-ethyl acetate-water, 16.2 + 18.8 + 52 + 3 ( v/v ), as mobile phase. Quantitative evaluation was by measurement of fluorescence-quenched zones by ultraviolet absorption scanning densitometry at λ = 254 nm. HPLC was performed on a C 18 column with an acetonitrile-0.5% acetic acid gradient as mobile phase, again with detection at λ = 254 nm. Quantitative evaluation was achieved by measurement of peak intensity. Both of methods were successfully used for determination of isoflavonoids in kudzu.

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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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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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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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To evaluate the reliability and applicability of chromatographic methods for fingerprinting, and for obtaining comprehensive information from the fingerprint, several chromatographic techniques including high-performance thin-layer chromatography (HPTLC), high-performance liquid chromatography (HPLC), and high-performance capillary electrophoresis (HPCE) have been used to obtain fingerprints of Pueraria Radix for the first time. The results showed that the relative standard deviation ( RSD ) of R F values, retention times, and peak-area percentages for samples of Pueraria lobata from different sources all perfectly satisfied the demands of the national standard, and HPTLC, HPLC, and HPCE have been successfully used for development of fingerprints of Pueraria Radix . When the chromatographic fingerprints established in this work were used to distinguish between authentic and fake Pueraria Radix by evaluation of similarity, different samples obtained from P. lobata and P. thomsonii were distinguished effectively. Although the three methods used for fingerprinting of Pueraria Radix were highly selective and reproducible, there were still significant reliability and applicability differences among the results obtained by use of these approaches, as is illustrated in this paper.

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A high-performance thin-layer chromatographic (HPTLC) method for simultaneous analysis of temephos and fenitrothion in green tea has been established and validated. The sample was extracted with ethyl acetate by mechanical vibration at room temperature and the extract was cleaned by use of an SPE tandem column, before elution with dichloromethane. The extract was applied as bands to glassbacked silica gel 60F254 HPTLC plates. The plates were developed with acetone-hexane 3+7 (v/v), in an unsaturated glass twin-trough chamber. The developed HPTLC plates were evaluated densitometrically. The detection limits of temephos (R F 0.55) and fenitrothion (R F 0.69) were 20 and 10 ng, respectively. Recovery from green tea of the two pesticides at levels of 0.2 to 4 mg kg−1 was 80–107% with relative standard deviations of 4.4–20.2%. The precision and accuracy of the method were generally fit for analysis of temephos and fenitrothion residues in green tea.

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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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