CHROMATOGRAPHIC QUANTITATION OF THE HYDROPHOBICITY OF IONIC COMPOUNDSBY THE USE OF MICELLAR MOBILE PHASES

Many biologically active compounds of interest in structure-activity r elationships are ionic at physiological pH. However, ionic organic com pounds are only weakly or not retained in conventional RPLC which impe des the chromatographic estimation of their hydrophobicity and the dev elopment of quantitative retention-activity relationship studies. The use of micellar mobile phases allows the retention of ionic compounds. Hydrophobic and electrostatic forces govern the retention of ionic co mpounds in micellar liquid chromatography. In this paper three differe nt retention models log k-log P for ionic compounds are tested (P=part ition coefficient). The retention model (log k=a log P+b alpha+c) whic h includes the hydrophobicity and the molar total charge of compound a t a given pH value has proven to be valid for all types of compounds t ested, catecholamines, local anesthetics, diuretics and o-phthalaldehy de-N-acetyl-L-cysteine amino acid derivatives. (C) 1998 Elsevier Scien ce B.V. All rights reserved.