Determination of parabens in cosmetic products by supercritical fluid extraction and capillary zone electrophoresis

Parabens are important additives in cosmetics for inhibiting the development of micro-organisms. However, most of the preservatives may be harmful to the consumers due to their potency to induce allergic contact dermatitis. Therefore, the assay for these substances in cosmetic products with high precision and accuracy is very important. This paper proposes a novel analytical method for the determination of four common parabens, namely, methyl p-hydroxybenzoate (MP), ethyl p-hydroxybenzoate (EP), propyl p-hydroxybenzoate (PP) and butyl p-hydroxybenzoate (BP) in cosmetic products. Parabens were extracted by supercritical fluid extraction (SFE) and followed by capillary zone electrophoresis (CZE). The optimum condition established for SFE was 40 degrees C, 12 100 kPa, CO2 with 0.05% acetonitrile and that for CZE was 30 mM sodium tetraborate in 5% acetonitrile (ACN), fused-silica capillary - 75 mu m, 60 cm, 25 kV, and at 30 degrees C. The recovery of SFE in the range 97.3-99.9% with good reproducibility (RSD=0.05-3.77%) was obtained. The CZE method offered a good resolution, R=1.70 and acceptable detection limits ranging from 0.97 to 1.33 ng for the parabens studied. The proposed method was applied to the determination of parabens in 11 creams by direct analysis and standard addition determination. (C) 1998 Elsevier Science B.V. All rights reserved.