Simultaneous determination of seven preservatives in cosmetics by dispersive liquid–liquid microextraction coupled with high performance capillary electrophoresis

Abstract

A simple, rapid, inexpensive and efficient method based on dispersive liquid–liquid microextraction (DLLME) coupled with high performance capillary electrophoresis (HPCE) has been developed for the extraction and determination of methylparaben (MP), ethylparaben (EP), propylparaben (PP), butylparaben (BP), sorbic acid (SOA), benzoic acid (BA), and salicylic acid (SA) in cosmetic products. A dispersive solution composed of 50 μL trichloromethane and 0.45 mL isopropyl alcohol was used to extract the target analytes from acidified sample solution quantitatively in the DLLME procedure. A suitable amount of lower layer was transferred into a vial and evaporated to dryness under nitrogen gas. The residue was reconstituted in methanol–water (20 : 80, v/v) solution, and separated using bare fused-silica capillary (50 μm i.d., 50 cm of total length, and 41 cm effective length) and detected at 230 nm. Urobenzoic acid was used as the internal standard. The calibration curves were linear in the range of 0.05 to 5.0 μg mL⁻¹ for MP and SA, and 0.025 to 5.0 μg mL⁻¹ for the rest with the coefficients of correlation ranging from 0.9978 to 0.9995. The limits of detection were in the range of 0.200–0.375 mg kg⁻¹ with enrichment factors ranging from 41 to 133 for all target analytes. Recoveries of the method were in the range of 71.1–112.6%, with the intraday RSDs and interday RSDs in the range of 2.22–4.51% and 3.05–4.89%, respectively. This method has been successfully applied for analysis of the preservatives in different samples of cosmetic.