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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Huba Kalász, Rafael Doležal, Kornélia Tekes, Kálmán Magyar, Tamás Csermely and Sándor Hosztafi

. Pliska, B. Testa, H. van de Waterbeemd (eds.), Lipophilicity in Drug Action and Toxicology, VCH, Weinheim, 1996, pp. 141–156. J.Z. Karasova, M. Pohanka, K. Musilek, F. Zemek, K. Kuca , Toxicol. In Vitro

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. 2007 20 261 265 R.F. Rekker and R. Mannhold , Calculation of Drug Lipophilicity. The Hydrophobic

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R.F. Rekker and R. Mannhold , Calculation of Drug Lipophilicity: The Hydrophobic Fragmental Constant Approach, Wiley-VCH, Weinheim, 1992. Mannhold R

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H. van de Waterbeemd, M. Kansy, B. Wagner , and H. Fisher in: V. Pliska, B. Testa , and H van de Waterbeemd (Eds) Lipophilicity in Drug Action and Toxicology, VCH, 1996, 73–106. R

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. 2001 55 1047 1074 R.F. Rekker and R. Mannhold , Calculation of Drug Lipophilicity, VCH, Weinheim

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The lipophilicity of twenty new diquinothiazines has been determined by reversed-phase thin-layer chromatography on RP-18 silica plates with acetone-aqueous TRIS (tris(hydroxymethyl) aminomethane) buffer as mobile phase. The R M values were linearly dependent on the concentration of acetone. The R M0 values were determined by linear extrapolation to 0% acetone. The experimental lipophilicity log P TLC was determined by use of a calibration plot obtained for six standards. The calculated lipophilicity log P calcd was obtained by use of the software ClogP and compared with experimental log P TLC values. Structure-lipophilicity relationships are discussed on the basis of the log P TLC values and the correlation between R M0 (intercept) and b (slope) of the TLC equation.

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H. van Waterbeemd, M. Kansy, B. Wagner, H. Fischer , in: V. Pliska, B. Testa, H. van Waterbeemd (eds), Lipophilicity in Drug Action and Toxicology, VCH, Weinheim, pp. 73–87, 1996

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. 1971 71 525 616 R.F. Rekker and R. Mannhold , Calculation of Drug Lipophilicity, VCH, Weinheim, 1992

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Lipophilicity is often estimated by thin-layer chromatography (TLC) as a fundamental property related to biological and pharmaceutical activity. In a recent study, we contributed some standardization to the subject by performing a comparative analysis of the different approaches in the field. This part presents an analogous study on silica, the use of which in normal-phase systems seems to be a new trend of recent times. We have compared several approaches of TLC lipophilicity determination: a single TLC run, Soczewiński-Wachtmeister equation coefficients, principal component analysis (PCA) of the retention matrix, and PARAFAC on a three-way array. All techniques were applied to 35 model solutes with simple molecules, using nine concentrations of six modifiers: acetone, dioxane, ethyl acetate, methylethylketone, propan-2-ol, and tetrahydrofuran. Comparative analysis points to several general recommendations. Ethyl acetate seems to give the best correlations with lipophilicity, and the correlations of single retention values, extrapolated values (intercepts), or C 0 are satisfactory (around 0.8) to use in normal-phase method in lipophilicity estimation. However, the correlation is quite worse and the normal-phase method should be treated as a method supplementary to the reversed-phase method. Neither PCA nor PARAFAC carried out on the retention matrix improved the correlations.

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Micellar liquid chromatography (MLC) has been used to study the lipophilicity of eight newly synthesized N-phenyltrichloroacetamide derivatives. Because the lipophilicity of a substance determines its retention and its interactions with micelles, chromatographic data calculated from experimental results — k m (log k m) — were compared with partition coefficients log P calculated from the molecular structures of the solutes. Micellar mobile phases containing Brij 35 and tetrahydrofuran, alkyl-bonded stationary phases, and two planar chromatography techniques — thin-layer chromatography (TLC) and over-pressured-layer chromatography (OPLC) — were used in the experiments. According to results obtained from the OPLC studies, especially, log k m values are excellent descriptors of the lipophilicity of the compounds. Very good linear relationships between log k m and log P were obtained by use of this technique (R in the range 0.917–0.987).

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