A gas chromatography–mass spectrometric method to determine skin-whitening agents in cosmetic products

An analytical method is proposed here to determine three allowed (kojic acid, azelaic acid and arbutin) and two forbidden (resorcinol and hydroquinone) skin-whitening agents in cosmetics. The method is based on gas chromatography coupled with mass spectrometric detection, which allows the two prohibited target compounds to be identified unequivocally by means of their mass spectra acquired in full-scan mode at the retention time of these compounds. Owing to their low volatility, target analytes are derivatized using N,O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA) (containing 1% trimethylchlorosylane) prior to injection into the chromatographic system. The accuracy and precision of the proposed method were evaluated by analysing a laboratory-made skin-whitening cosmetic sample containing known amounts of the five target compounds. The method can be easily applied by the manufacturers in the quality control of their own products, and also by safety authorities to prevent fraudulent operations and thus look after consumers’ health. The proposed method was successfully applied to the analysis of nine commercial skin-whitening cosmetic products, showing that fraud was committed in four of the analyzed samples.