PARABENS LIPOPHILICITY DETERMINATION WITH MOBILE PHASES CONTAINING LOW AND MEDIUM HYDROPHOBIC ALCOHOLS

Abstract

The efficiency of low and medium hydrophobic alcohols as mobile phase additives for lipophilicity determination of parabens was investigated using reversed-phase liquid chromatography and C18 chromatographic column as stationary phase. The eluting strength was evaluated by methylene selectivity determination for different mobile phases, containing water (0.1% H3PO4)-hydrophobic alcohols mixtures, starting with methanol and continued with methanol with 1% upper alcohols (differing through one methylene group, from ethanol to octanol) as organic additive. A good linear dependence (R 2 > 0.99) was observed between the retention factors (log k) and the organic content of the mobile phase in all cases. Several methodologies such as arithmetic mean computation of experimental retention values, extrapolation to zero methanol concentration procedure, and principal component analysis were applied to retention data values in order to determine relevant parameters [mlog k - mean of experimental retention values log k, log kw – extrapolated capacity factor to 100% water, and respectively PC1/log k (scores corresponding to the first principal component)]. The evaluation of the experimental lipophilicity parameters revealed a significant correlation with the reference octanol–water partition coefficients (log Kow) and also with various computed lipophilicity parameters (log P).