ABSTRACT
Lipophilicity is one of the properties which influences the partition of a substance in biological media. The present study reports on the chromatographic behaviour of a newly synthesised series of furan derivatives by RP-HPLC and RP-TLC, with methanol-water and acetonitrile-water as mobile phases, in order to establish if the linear relationships between the retention parameters (log k, R(M)) and the concentration of organic modifier in the mobile phase, phi, allows the extrapolation procedure. Good correlations between the retention parameters were obtained by RP-HPLC and RP-TLC, and the concentration of organic modifier (methanol, acetonitrile) in the mobile phase was established for the studied furan derivatives. However, for the discussed compounds, acetonitrile has a lower sensitivity to changes in the structures. A good correspondence was obtained between the extrapolated parameters for the methanol-water mobile phase when using RP-HPLC and RP-TLC. However, stronger interactions occur in RP-TLC between the compounds and the residual silanol groups than in RP-HPLC.
Subject(s)
Chromatography, High Pressure Liquid/methods , Furans/analysis , Lipids/chemistry , Chromatography, Thin Layer , Spectrophotometry, UltravioletABSTRACT
The partition coefficients, P, between n-octanol and water of a number of growth stimulating substances, N-hydroxyethylamide of aryloxyalkylen- and pyridine carboxylic acids were obtained from Pomona College (C log P), and Rekker's (log P(Rekker)) revised fragmental constant system was used to calculate log P data sets. Both of these data sets were correlated with two different substance lipophilicity parameters, log k(w) and phi0. Log k(w) was obtained by extrapolation of log retention factor (k) to 0% organic modifier measured in reversed-phase liquid chromatography (RPLC) systems. Phi0 values were obtained from the slopes and intercepts of these relationships. The RPLC experiments were performed on four commercially available reversed-phase columns. Binary mixtures of methanol-water, methanol-phosphate buffer (pH 7.0), methanoltricine buffer (pH 7.0) and acetonitrile-water were used as mobile phases for the determination of log k(w) values. For the methanolic eluents linear regression provided satisfactory correlations (r>0.99) for the relationships log k vs. organic modifier content in the eluent, while for the acetonitrile-containing eluents a second-degree polynominal regression was necessary. For all four RPLC columns, by linear regression satisfactory correlations (r>0.99) were obtained between log k(w) and log P data using methanolic eluents. In such eluents phi0 values were shown to be the second-best lipophilicity parameters. For acetonitrile-containing eluents the use of second-degree polynominal regression was necessary and, in contrast to methanol, significant influence of the applied column on regression results was observed. For acetonitrile-containing eluents the phi0-index does not provide satisfactory results for our substances. No difference in regression results between the use of buffered and non-buffered eluents was observed.
Subject(s)
Amides/chemistry , Carboxylic Acids/analysis , Chromatography, High Pressure Liquid/methods , Carboxylic Acids/chemistry , Spectrophotometry, UltravioletABSTRACT
The separation of ten plant extracts using automated multiple development thin-layer chromatography (AMD -TLC) is described. Alcoholic extracts were obtained from Cinchona succirubra, Aesculus hippocastanum, Berberis vulgaris. Artemisia abrotanum, Carduus marianus, Thuja occidentalis, Baptisia tinctoria, Paulinia cupana, Lycopus europaeus and Echinacea angustifolia. The separation was performed on silica plates (Sil G-50 UV 254 (Macherey-Nagel), 10 x 20 cm). AMD was achieved in 25 steps using methanol, ethyl acetate, toluene, 1,2-dichloroethane, 25% ammonia solution and anhydrous formic acid as modifiers. The chromatograms were evaluated with a Shimadzu CS-9000 dual-wavelength flying-spot scanner. Better separations were obtained using AMD than isocratic elution.
