A New Method for HPLC Analysis of Surfactants Present in Shampoos and Hair-Conditioners

Abstract

A New method for analyzing ionic and nonionic surfactants present in shampoos and hair-conditioners is proposed; a combination of the ordinary photometry with differential refractometry as the detector of reversed-phase high-performance liquid chromatography (HPLC). A ratio of the area intensity of the UV absorption to that given by differetial refarctometry (UV/RI ratio) was found to be specific to each surfactant. When the UV/RI ratios were plotted against the retention-time (Rt) for various authentic surfactants, location of a spot in the UV/RI-vs-Rt map was specific to each surfactant and there was no overlapping between spots even for two similar surfactants which are usually overlapped in the UV-vs-Rt map. Accordingly, the UV/RI-vs-Rt map obtained for an arbitrary mixture of surfactants allowed more accurate analysis of surfactants than the ordinary method based solely on the retention time. In fact, when model shampoos and hair-conditioners using anionic, cationic, amphoteric and nonionic surfactants were analyzed with methanol-water as a mobile phase on the ODS column, the analytical values from the present method were quantitatively successful.