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A simple and precise reversed-phase thin-layer chromatographic (RP TLC) method for simultaneous separation of fluoxetine and citalopram in pharmaceutical preparations has been developed and validated. Separation was performed on RP-18 F254 TLC plates with methanol-0.05 M phosphate buffer (pH 5)-triethylamine 68:27:5 (v/v) as mobile phase. Densitometric detection was performed at 230 nm. The method was validated for linearity, accuracy, precision, selectivity, and robustness. Calibration plots showed the response, as peak area, was a linear (r 2 > 0.9988) function of the amounts of the compounds in the concentration range 500–5000 ng per spot. Statistical analysis proved the method was both precise and accurate. The method was successfully used for analysis of citalopram and fluoxetine in their pharmaceutical preparations, with recovery of the compounds ranging from 99.10 to 101.70% of the labeled amount.

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Selected meta - and para -alkoxyphenols have been separated by RP TLC on cellulose impregnated with ethyl oleate, with ethanol-water, 25 + 75 and 40 + 60 (%, v/v ), as mobile phases. The R M values of the alkoxyphenols have been correlated with structural descriptors based on the adjacency matrix ( 2 χ v , 2 χ v , and χ 012 ), on the distance matrix ( W , A , 0 B , 1 B , D , C , 2 B , 3 B q , 3 B , 3 B q , I B ), and on electrotopological states (SssO, ScCH 3 , SaaCH, SaasC, SsOH). Most accurate prediction of the R M values of the all alkoxyphenols was achieved by use of second-or third-degree polynomial correlation equations with one structural descriptor from among the topological indexes W , A , 1 B , D , 3 χ v , and I B . The best correlation equations for prediction of R M values separately for meta - and para -alkoxyphenols were been obtained by use of the topological indexes 2 χ v , C and χ 012 .

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Evaluation of the lipophilicity of derivatives of N -benzylamides and N -phenylethylamides of α -(1,2,3,4-tetrahydroisoquinolin-2-yl)- γ -hydroxybutyric acid is described. Reversed-phase thin-layer chromatography (RP-TLC) was performed on RP-18 F 254S plates with mixtures of methanol and water as mobile phases. Retention data ( R M ) obtained by use of this method were linearly dependent on methanol concentration and enabled estimation of relative lipophilicity ( R M0 ) corresponding to pure water as mobile phase. R M0 values were compared with partition coefficients (log P ) obtained by use of several computational methods (Pallas, ScilogP, ChemOffice, and Daylight software). log P values estimated by use of Pallas software correlated best with experimental data. Comparison of relative lipophilicity ( R M0 ) and anticonvulsant activity (maximal electroshock seizure model in mice) of derivatives containing a rigid 1,2,3,4-tetrahydroisoquinoline substituent in the α position (series A and B) with values for their flexible analogs indicated that, for all the molecules, this rigid substituent resulted in reduced lipophilicity and reduction or loss of activity.

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The chromatographic behavior of series of azo-dye derivatives has been studied by RP C 18 TLC with water-methanol, water-acetone, water-dioxane, and water-acetonitrile mobile phases. The mechanism of retention was investigated and the retention constants, R M 0 , were determined by extrapolation. Correlations between retention constants, R M 0 , and lipophilicity, C 0 ( C 0 = R M 0 /m) and log P (ACD log P ) were investigated. Better correlations were obtained between C 0 and log P than between R M 0 and log P . These C 0 values may be use as a measure of the lipophilicity of the compounds investigated.The effect of mobile phase pH on retention of azo-dye derivatives was studied in RP C 18 TLC with diluted acetic acid-methanol, 20 + 30 ( v/v ) as mobile phase. Different methods were used to measure mobile phase pH. p K a values were determined on the basis of the relationships between analyte retention and mobile phase pH. Because the investigated azo dyes are newly synthesized compounds these p K a values have been determined for the first time. Correlations between p K a , and log P are discussed.

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The lipophilicity of fifteen anticancer-active propargyl thioquinolines has been determined by reversed-phase thin-layer chromatography with mixtures of acetone and Tris buffer, pH 7.4, as mobile phases. The R M values of the compounds decreased linearly with increasing concentration of acetone in the mobile phases. The partition coefficients (log P ) of the propargyl thioquinolines were calculated by use of the ScilogP program. Comparison of R M0 and log P ScilogP values enabled calculation of c log P values. It was found that the c log P values of the compounds correlated with their in vitro anticancer activity, expressed as ID 50 [μg mL −1 ], against a breast cancer cell line (T47D).

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Higher fatty acids, hydroxy fatty acids, and their esters have been separated by reversed-phase thin-layer chromatography with three mobile phases. The partition coefficients ( A log P s, IA log P , C log P , log P Kowin , x log P , and log P Rek ) were calculated for the compounds by use of different theoretical procedures. New methods for calculation of partition coefficients on the basis of experimental R M values have been proposed. These methods lead to different partition coefficients for oleic and elaidic acids, geometric isomers of 9-octadecenoic acids.

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M. Stefaniak, A. Pyka , and J. Śliwiok , Application of the R F values and topological indices to modify log P according to Rekker of selected porphyrins and metalloporphyrins separated by the RP-TLC technique, Planar Chromatography

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RP-TLC retention behavior has been studied for a series of potential antituberculotic drugs from a group of substituted anilides of pyrazine-2-carboxylic acid. Lipophilicity was determined by use of reversed-phase thin-layer chromatography with methanol-water mobile phases. R MW values were obtained by extrapolation of R M (determined by RP-TLC) to methanol-free conditions. These experimental lipophilicity values were correlated with lipophilicity (log P ) calculated by use of three software products. Good correlation was obtained between R MW and log P . The results of this study could be used in further experiments focused on investigation of the biological activity of these newly prepared compounds and other potential antituberculotic drugs with closely similar chemical structures.

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We describe a simple and inexpensive SPE-RP-TLC method for the monitoring and analysis of haloperidol and its metabolites in plasma. Analysis was carried out on RP-TLC plates containing C18 silica gel using methanol having 0.001% diethylamine as a mobile phase. The chromatograms were developed up to 10 cm for 65 min at 28 ± 10°C. Detection of haloperidol and its metabolites was done by placing the dried plates in normal glass iodine chamber. The quantitative analysis of haloperidol and its metabolites were carried out by using UV-visible spectroscopy at 230 nm. R F values of haloperidol, metabolite I, metabolite II, and metabolite III in plasma samples were 0.22, 0.06, 0.16, and 0.87, respectively, and their percentage recoveries were 85.0, 88.0, 87.0, and 77.0, respectively. The detection limit of RP-TLC method for haloperidol was 1.0 mg mL−1 and for all the three metabolites I, II, III was 0.8 mg mL−1. The results show that the developed method may be used for higher recovery of drugs under consideration from biological samples.

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log P values of 29 biologically active chalcone (1) and cyclic chalcone analogues E -2-(X-benzylidene)-1-indanones (2) and E -2-(X-benzylidene)-1-tetralones (3) have been determined by an optimized and validated RP-TLC method. RP-TLC was performed on silanized silica gel 60F 254 as stationary phase with methanol-water, 60 + 40 ( v/v ) as mobile phase. The RP-TLC method was validated by analysis of three drugs, diazepam, progesterone, and PGE 1 ethyl ester, with known log P SF (shake-flask) values. The experimentally determined log P TLC values were compared with the log P values predicted by use of the CLOGP program. On the basis of the log P TLC values of the investigated chalcones (1), the cyclic chalcone analogues (2, 3), and previously investigated, related, E -2-(X-benzylidene)-1-benzosuberones (4) the effect on lipophilicity of ring size and the nature and position of substituents were studied. It was found that the open-chain chalcones (1) and the five-membered ring E -2-(X-benzylidene)-1-indanones (2) have similar lipophilicity. Changing the ring size from five to six (3) and from six (3) to seven (7) resulted in the expected increase of the log P values of the compounds. The results indicate importance of steric and electronic factors in the lipophilicity of the compounds investigated.

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