ROLE OF STATIONARY-PHASE AND ELUENT COMPOSITION ON THE DETERMINATION OF LOG P VALUES OF N-HYDROXYETHYLAMIDE OF ARYLOXYALKYLEN-CARBOXYLIC-ACIDS AND PYRIDINE-CARBOXYLIC-ACIDS BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

The partition coefficients, P, between n-octanol and water of a number of growth stimulating substances, N-hydroxyethylamide of aryloxyalkyl en- 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 c orrelated with two different substance lipophilicity parameters, log k (w) and phi(o). Log k(w) was obtained by extrapolation of log retentio n factor (k) to 0% organic modifier measured in reversed-phase liquid chromatography (RPLC) systems. phi(o) values were obtained from the sl opes and intercepts of these relationships. The RPLC experiments were performed on four commercially available reversed-phase columns. Binar y mixtures of methanol-water, methanol-phosphate buffer (pH 7.0), meth anol-tricine buffer (pH 7.0) and acetonitrile-water were used as mobil e 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 polyno minal regression was necessary. For all four RPLC columns, by linear r egression satisfactory correlations (r>0.99) were obtained between log k(w) and log P data using methanolic eluents. In such eluents phi(o) values were shown to be the second-best lipophilicity parameters. For acetonitrile-containing eluents the use of second-degree polynominal r egression was necessary and, in contrast to methanol, significant infl uence of the applied column on regression results was observed. For ac etonitrile-containing eluents the phi(o)-index does not provide satisf actory results for our substances. No difference in regression results between the use of buffered and non-buffered eluents was observed. (C ) 1998 Elsevier Science B.V. All rights reserved.