Simultaneous multiple-development HPTLC quantification of water- and oil-soluble sunscreens

Abstract

Acomplex mixture of sunscreens of different lipophilicity was quantified for the first time by thin-layer chromatography (TLC) followed by densitometric scanning in absorption mode. Multiple-development normal-phase TLC was performed on silica gel 60 as stationary phase. Two mobile phases were used: A — cyclohexane-diethyl ether 5:1 (v/v) and B — ethyl acetate-ethanol-water 70:35:30 (v/v). After development with mobile phase A, two oil-soluble sunscreens, avobenzone (AVO) and octyl salicylate (OS), were analyzed at 360 and 300 nm, respectively. Subsequent development of the same plates with mobile phase B made it possible to quantify a water-soluble sunscreen — phenylbenzimidazol sulfonic acid (PBS) at 300 nm. Calibration curves were non-linear. Limits of detection (LOD) and quantification (LOQ) were LOD (OS) 0.02 μg spot−1, LOQ (OS) 0.06 μg spot−1, LOD (AVO) 0.03 μg spot−1, LOQ (AVO) 0.08 μg spot−1, LOD (PBS) 0.02 μg spot−1, and LOQ (PBS) 0.06 μg spot−1. The method was validated and applied to the analys...