Determination of α-hydroxy acids in cosmetics by UHPLC-MS/MS

Objective To establish a UHPLC-MS/MS quantitative method for the determination of glucuronic acid， tartaric acid， glycolic acid， malic acid， lactic acid， citric acid， DL-2-hydroxybutyric acid sodium， mandelic acid， benzilic acid， hydroxycaprylic acid， lactobionic acid， gluconic acid and N-acetylneuraminic acid in cosmetics.

Methods Samples were prepared by ultrasonic extraction， cleansed by precipitating reagent and followed by high-speed centrifugation of the extraction solution. The supernatant was filtered by 0.22 μm Millipore filter. The continued filtrate was taken for analysis. A reversed phase column， Poroshell 120 EC-C₁₈ （2.7 μm， 4.6 mm×1 000 mm） was used with 0.1% formic acid buffer and acetonitrile as the mobile phase under the condition of gradient elution. The analytes were detected with electrospray ionization source in negative ion mode （ESI^-） and multiple reactions monitoring （MRM）， and quantified by external standard curve.

Results The method showed a good linearity of glucuronic acid， tartaric acid， malic acid， DL-2-hydroxybutyric acid sodium， benzilic acid， hydroxycaprylic acid and N-acetylneuraminic acid within the concentration range of 50.0‒2 000.0 μg·L^-1 （r>0.995）. The method showed a good linearity of glycolic acid， lactic acid， citric acid and mandelic acid within the concentration range of 100.0‒5 000.0 μg·L^-1 （r>0.995）. The method showed a good linearity of lactobionic acid and gluconic acid within the concentration range of 50.0‒5 000.0 μg·L^-1 （r>0.995）. The recoveries were in the range of 92.3%‒114.1%； the relative standard deviations （RSD） were in the range of 0.9%‒6.0% （n=3）. The detection limits of glucuronic acid， tartaric acid， malic acid， citric acid， DL-2-hydroxybutyric acid sodium， mandelic acid， benzilic acid， hydroxycaprylic acid， lactobionic acid， gluconic acid and N-acetylneuraminic acid were 0.003% while the detection limits of glycolic acid， lactic acid and mandelic acid were 0.006%. In 10 batches of commercially available cosmetics， eight batches showed positive result.

Conclusion The UHPLC-MS/MS method is efficient， sensitive and accurate and is applicable to the determination of 13 α-hydroxy acidic components in cosmetics.