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  • Author or Editor: Feng Tang x
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For the purpose of qualitative and quantitative analysis of flavonoids from eight species of Indocalamus, Indocalamus latifolius (Keng) McClure, I. herklotsii McClure, I. decorus Q. H. Dai, I. barbatus McClure, I. sinicus (Hance) Nakai, I. longiauritus Hand.—Mazz, I. guangdongensis H. R. Zhao et Y. L. Yang, I. pedalis (Keng) Keng f., a simple, efficient, accurate and low-cost method was constructed. Six flavonoids, vitexin, isovitexin, orientin, isoorientin, quercetin and tricin, were selected as marker flavonoids. The multistage development was performed in Automated Multiple Development (AMD2) and solvents in different ratios were used as mobile phase. The developed plates were scanned by TLC Scanner3. The components separated well and RF values of the six marker flavonoids were 0.22, 0.31, 0.38, 0.45, 0.57, and 0.88, respectively. The method was validated for precision, accuracy, selectivity and repeatability, which were expressed as coefficient of variation (CV [%]). The concentrations and kinds of flavonoids were significantly different in these six species of Indocalamus. The concentration of total flavonoids in the dry leaves was in the range of 0.11–0.40%, and the decreasing order of concentration was I. barbatus, I. sinicus, I. longiauritus, I. guangdongensis, I. decorus, I. pedalis, I. latifolius, I. herklotsii; the concentration of total flavonoids in I. barbatus was the maximum among these eight species of Indocalamus, and they would be more useful in extracting natural bamboo flavonoids.

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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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Flavonoids are the main functional compounds in a bamboo leaf extract. Because of their activity flavonoids are widely used in many of health products, cosmetics, and food supplements. A simple high-performance thin-layer chromatographic (HPTLC) method has been established for simultaneous quantification of vitexin, isovitexin, orientin, and isoorientin in the leaves of three different bamboo species: Phyllostachys pubescens Mazel ex H. de Lehaie, Phyllostachys glauca McClure, and Pleioblastus yixingensis S. L. Chen et S. Y. Chen. The method was validated for precision (expressed as the coefficient of variation, CV [%]), accuracy, sensitivity, and selectivity. Instrumental precision was found to be 0.37, 0.52, 0.39, 0.13, and 0.84% and the repeatability of the method 0.98, 0.91, 1.02, 1.04 and 0.87% for isovitexin, rutin, orientin, isoorientin, and vitexin, respectively. The accuracy of the method was determined by measurement of recovery at three different concentrations. Average recovery was 99.54% for isovitexin, 99.31% for orientin, and 100.55% for isoorientin from P. pubescens; 98.97% for orientin, 99.00% for isovitexin, and 99.58% for vitexin from P. glauca ; and 98.86% for orientin, 100.04% for isoorientin, and 99.63% for vitexin in P. yixingensis . In the fraction extracted from bamboo leaves known as Flavone Gruff the flavonoid content was 6.44% ( w/w ) for orientin, 3.45% for isovitexin, and 6.58% for isoorientin in P. pubescens ; 7.82% for orientin, 2.82% for isovitexin, and 13.7% for vitexin in P. glauca ; and 4.92% for orientin, 3.50% for isoorientin, and 22.5% for vitexin in P. yixingensis . Although the presence of rutin was confirmed in the bamboo leaves investigated, it could not be quantified because of its low concentration. The proposed HPTLC method was found to be simple, precise, selective, sensitive, and accurate for routine quality control of the leaves of different bamboo species and formulations containing bamboo-leaf flavonoids.

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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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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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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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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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