A new treatment by dispersive liquid-liquid microextraction for the determination of parabens in human serum samples

Alkyl esters of p-hydroxybenzoic acid (parabens) are a family of compounds that have been in use since the 1920s as preservatives in cosmetic formulations, with one of the lowest rates of skin problems reported in dermatological patients. However, in the last few years, many scientific publications have demonstrated that parabens are weak endocrine disruptors, meaning that they can interfere with the function of endogenous hormones, increasing the risk of breast cancer. In the present work, a new sample treatment method is introduced based on dispersive liquid-liquid microextraction for the extraction of the most commonly used parabens (methyl-, ethyl-, propyl-, and butylparaben) from human serum samples followed by separation and quantification using ultrahigh performance liquid chromatography-tandem mass spectrometry. The method involves an enzymatic treatment to quantify the total content of parabens. The extraction parameters (solvent and disperser solvent, extractant and dispersant volume, pH of the sample, salt addition, and extraction time) were accurately optimized using multivariate optimization strategies. Ethylparaben ring (13)C6-labeled was used as surrogate. Limits of quantification ranging from 0.2 to 0.7 ng mL(-1) and an interday variability (evaluated as relative standard deviations) from 3.8 to 11.9 % were obtained. The method was validated using matrix-matched calibration standard and a spike recovery assay. Recovery rates for spiked samples ranged from 96 to 106 %, and a good linearity up to concentrations of 100 ng mL(-1) was obtained. The method was satisfactorily applied for the determination of target compounds in human serum samples.