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  • Author or Editor: Dorina Casoni x
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A thin-layer chromatographic (TLC) procedure combined with digital image processing analysis was developed for quantitative time-monitoring of the radical- scavenging activity. Reaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH•) with reference antioxidants and selected catecholamine compounds was monitored on RP-18 chromatographic plates using dot-blot technique and different concentrations of standards. Images of the chromatographic plate were recorded after background staining every 5 min for 1 h using a TLC scanner device. ImageDecipher TLC software program was used to convert image data into chromatograms, from which spot area as a function of reaction time was easily monitored for different amounts of antioxidant in all cases. For a comparative evaluation of radical-scavenging activity, all the time-acquired images were documented as a new red, green, and blue (RGB) image after conversion to different color values. Based on the chromatogram digitization results, TLC—time-monitored radical-scavenging profiles of the investigated compounds were obtained. By the developed methodology, different image processing and image analysis procedures were proposed and originally applied for the first time in TLC—time-monitoring of radical-scavenging activity evaluation.

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A facile and rapid thin-layer chromatography (TLC) method for tartrazine analysis from mustard is proposed. Silica gel precoated plates and isopropyl alcohol-ammonia mixture as mobile phase were used for tartrazine determination. The synthetic dye was extracted from solid matrix by ultrasound assisted extraction with a methanol-ammonia mixture and further purified by ion-pair solid phase extraction, using hexadecyltrimethylammonium-bromide as ion-pair reagent. Recovery determination was carried out on mustard samples spiked with tartrazine at different concentration levels. Good recoveries, around 98%, and a relative standard deviation of 17.4% were obtained. An extensive study for the quantitative evaluation of dyes was developed by comparing the photodensitometric results with those obtained by using digital processing of scanned plates with ImageDecipher-TLC software. The method was applied for the tartrazine determination in various mustard samples purchased from a local market.

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The thin-layer chromatographic (TLC) separation of rare earths has been studied using di(2-ethylhexyl)dithiophosphoric acid as complexing agent in the mobile phase. Silica gel H and silica gel H impregnated with 2.5 m NH 4 NO 3 were investigated as stationary phases. The TLC behavior of rare earths on these adsorbents was compared using different mixed mobile phases. The best results were obtained by use of ethyl methyl ketone-tetrahydrofuran-di(2-ethylhexyl)dithiophosphoric acid (1 m ), 6.8 + 3.2 + 0.4 ( v/v ), as mobile phase. Double development was used to achieve better separation of consecutive rare earths.

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