Determination of Parabens in Cosmetics by Liquid-Phase Microextractions and High-Performance Liquid Chromatography-Diode Array Detection

To deal the stubborn problem arising from oily matrix of cosmetics in the chromatography of parabens, an efficient, rapid, and economic sample preparation method is proposed involving separation of matrix material by extraction with 1mL of isooctane/1-octanol (50:50, v/v) in the presence of 1mL of 1mol/L sodium hydroxide, and centrifugation. Then, parabens in the alkaline solution were preconcentrated, after acidification, by liquid-liquid-liquid microextraction using 200 mu L of isooctane/1-octanol (50:50, v/v) as organic solvent and 5 mu L of 0.1mol/L of sodium hydroxide as the acceptor drop. Using the optimized procedure, the method provided a rectilinear graph for 0.01-8mg/kg of parabens with correlation coefficient (r) in the range 0.9982-0.9990, limit of detection in the range 1.7-4.3 mu g/kg, and enrichment factor in the range 79-118. Intra-day (and inter-day) RSD at 0.01 and 5mg/kg spiked levels of parabens were found as 7.7% (9.2%) and 4.7% (5.6%), respectively. Average recovery of spiked amounts of parabens to cosmetics was 98.9% with an average RSD of 6.1%. A distinct superiority of the present method in terms of sensitivity attained for parabens was evident over HPLC and CE methods that used UV detection, and some others where mass spectrometric detection was used.