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  • Author or Editor: Costel Sârbu x
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A comparative QSAR and QSRR study has been conducted by multiple linear regression (MLR), principal-component regression (PCR), and partial least-squares (PLS) analysis. Comparisons based on these regression methods have been used to model the chromatographic retention (lipophilicity) of thirteen new oxadiazoline derivatives by means of descriptors obtained by use of the Alchemy software package. Retention indices were determined by reversed-phased high-performance thin-layer chromatography on C 18 plates. The retention indices predicted were quite satisfactory and in very good agreement with the molecular structure of the compounds investigated.

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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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Chromatographic retention data R F and R M 0 of some benzimidazole and benztriazole derivatives have been estimated by reversed-phase thin-layer chromatography on paraffin oil-impregnated silica gel plates with methanol-water mixtures as mobile phases. A quantitative structure-retention relationship (QSRR) correlation study was performed on a matrix containing retention data derived from chromatographic regression, retention scores provided by principal-components analysis (PCA), and different computed molecular descriptors. By means of multiple regression analysis statistically significant equations relating lipophilicity (estimated as R M 0 values) to different descriptors were derived for the sixteen compounds.

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Reversed-phase (RP) HPTLC with aqueous ammonia-organic modifier (acetonitrile, dioxane, acetone) mobile phases has been used to study the effect on retention of the chromatographic system and the physicochemical properties of twelve 2,4-dioxotetrahydro-1,3-thiazoles. A multivariate approach to the retention behavior of these 1,3-thiazoles with three quite different organic solvents was used to explain the interactions between the analytes and the mobile phases. Principal-component analysis (PCA) and partial least-squares (PLS) regression were used to determine the molecular properties with the greatest effect on retention for each modifier. Good correlation was obtained between experimental and calculated retention data.

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