Determination of chlorphenesin in cosmetics, a preservative that can affect anti-doping test result interpretations.

Chlorphenesin is a legitimate preservative commonly used in cosmetics. It shares one urinary metabolite of 4-chlorophenoxyacetic acid with meclofenoxate, a prohibited stimulant in sports. Recently, there have been cases where athletes using chlorphenesin-containing products were falsely identified as users of meclofenoxate. This study developed and validated a liquid chromatography method with diode-array detection to determine the chlorphenesin content in 61 selected personal care products with various functions (e.g., facial care, body cleansing, sun protection, make-up, hairstyling, perfume, and oral cleaning). The analytical method demonstrated fit-for-purpose quantitation and provided good linearity, precision, accuracy, and recovery for analyzing different cosmetic matrices. Among the 27 cosmetics labeled with chlorphenesin, the chlorphenesin concentrations ranged from 0.10 to 2.67 mg/g, with three products showing no detection. None of the products exceeded the maximum limit of 3 mg/g (0.3%) set by regulatory authorities. Among the 34 cosmetics not labeled with chlorphenesin, none of them contained chlorphenesin. This study confirmed the absence of undeclared chlorphenesin in the selected cosmetics, supporting the correctness of chlorphenesin labeling in cosmetics sold in Taiwan. Further investigations studying urinary excretion patterns after different types, doses, frequencies, and sites of cosmetics applications could contribute to strengthen current testing approaches in anti-doping.