Determination of benzophenone-3 and its main metabolites in human serum by dispersive liquid-liquid microextraction followed by liquid chromatography tandem mass spectrometry

A new analytical method for the determination of benzophenone-3 (2-hydroxy-4-methoxybenzophenone), and its main metabolites (2,4-dihydroxybenzophenone and 2,2'-dihydroxy-4-methoxybenzophenone) in human serum is presented. The method is based on dispersive liquid-liquid microextraction (DLLME) as preconcentration and clean-up technique, followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Acidic hydrolysis and protein precipitation with HCl 6 M (1:1) (100 °C, 1 h) were carried out before extraction. The variables involved in the DLLME process were studied. Under the optimized conditions, 70 µL of acetone (disperser solvent) and 30 µL of chloroform (extraction solvent) were mixed and rapidly injected into 800 µL of hydrolyzed serum sample. Sample pH or ionic strength adjustment were not necessary. The method was validated by analyzing spiked human serum samples. No satisfactory recoveries were obtained when aqueous standards or standards prepared in synthetic serum were used, but excellent recoveries were achieved by using matrix-matched calibration standards. Moreover, limits of detection in the low µg L−1 level and good repeatability were obtained. In order to show the applicability of the proposed method in the study of percutaneous absorption processes, it was applied to the analysis of serum samples from two volunteers after topical application of a sunscreen cosmetic product containing 2-hydroxy-4-methoxybenzophenone.