Determination of p-aminobenzoates and cinnamate in cosmetic matrix by supercritical fluid extraction and micellar electrokinetic capillary chromatography

p-Aminobenzoates (PABAs) and cinnamate are useful UV-absorbers in cosmetic products as protection against harmful UV radiation. A novel analytical method for the determination of p-aminobenzoate and cinnamate UV-absorbers was proposed. They were extracted by supercritical fluid extraction (SFE) and then analyzed by micellar electrokinetic capillary chromatography (MECC) and high performance liquid chromatography (HPLC). Methanol and acetic acid were used as modifier in SFE. The recovery of SFE in the range 98.43-101.83% with good reproducibility (relative standard deviation, R.S.D.=0.94-1.77%) were obtained. The MECC method offered a good resolution (Rs=1.44) and acceptable detection limits ranging from 157 to 828 ng/ml. A comparison between the results obtained by MECC with HPLC was made. With regard to specificity, sensitivity and reproducibility, the results of HPLC was better than capillary electrophoresis (CE). But CE is more rapid, effective and economical than HPLC. The proposed analytical techniques were applied to the determination of PABA and cinnamate in 10 commercial sunscreen products using direct analysis and standard addition determination. These two results for identical samples are similar. (C) 2000 Elsevier Science B.V. All rights reserved.