EFFECT OF PH ON THE RETENTION BEHAVIOR OF SOME PRESERVATIVES-ANTIOXIDANTS IN REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

In this paper the dependence of eluent pH on the efficiency of separat ion in RP-HPLC is described. Preservatives-antioxidants, esters of p-h ydroxybenzoic acid (methyl, ethyl, propyl and butyl parabens), sorbic acid, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG) and L-ascorbic acid (Vitamine C) were investigated by reversed-phase highperformance liquid chromatography, utilising is ocratic elution with UV detection. The mobile phase composition (metha nol-water v/v containing 1 % acetic acid), was varied in order to obta in the best separation. For all substances analysed the pH, pKa and th e fitted pKa values were calculated in different mixtures of mobile ph ases using the graphical method of Chariot and Tremillon [1]. The rete ntion factors (k) and the separation factors (alpha) were also calcula ted.