Development and Optimization of an analytical method for the determination of UV filters in suntan lotions based on microemulsion electrokinetic chromatography

Microemulsion electrokinetic chromatography (MEEKC) has been applied to the separation of some UV filters (Eusolex 4360, Eusolex 6300, Eusolex OCR, Eusolex 2292, Eusolex 6007, Eusolex 9020, Eusolex HMS, Eusolex OS, and Eusolex 232) commonly found in suntan lotions. The composition of the microemulsion employed was optimized with respect to the best possible separation of the selected analytes using artificial neural networks (ANNs). Two parameters namely the composition of the mixed surfactant system comprising the anionic sodium dodecyl sulfate (SDS) and neutral Brij 35 and the amount of organic modifier (2-propanol) present in the aqueous phase of the microemulsion were modeled. Using an optimized MEEKC buffer consisting of 2.25 g SDS, 0.75 g Brij 35, 6.6 g 1-butanol, 0.8 g n-octane, 17.5 g 2-propanol, and 72.1 g of 10 mM borate buffer (pH 9.2), eight target analytes could be separated in under 25 min employing a diode-array detector to segregate the overlapping signals obtained for Eusolex 9020 and Eusolex HMS. Detection limits from 0.8 to 6.0 μg/mL were obtained and the calibration plots were linear over at least one order of magnitude. The optimized method could be applied to the determination of Eusolex 6300 and Eusolex 9020 in a commercial suntan lotion.