Large volume sample stacking with EOF and sweeping in CE for determination of common preservatives in cosmetic products by chemometric experimental design.

This study proposes a capillary electrophoresis method incorporating large volume sample stacking, EOF and sweeping for detection of common preservatives used in cosmetic products. The method was developed using chemometric experimental design (fractional factorial design and central composite design) to determine multiple separation variables by efficient steps. The samples were loaded by hydrodynamic injection (10 psi, 90 s), and separated by phosphate buffer (50 mM, pH 3) containing 30% methanol and 80 mM SDS at -20 kV. During method validation, calibration curves were found to be linear over a range of 5-100 µg/mL for butyl paraben and isobutyl paraben; 0.05-10 µg/mL for ethyl paraben; 0.2-50 µg/mL for dehydroacetic acid; 0.5-70 µg/mL for methyl paraben; 5-350 µg/mL for sorbic acid; 0.02-450 µg/mL for p-hydroxybenzoic acid and 0.05-10 µg/mL for salicylic acid and benzoic acid. The analytes were analysed simultaneously and their detection limits (S/N = 3) were down to 0.005-2 µg/mL. The analysis method was successfully used for detection of preservatives used in commercial cosmetics.