Analysis of oestrogenic compounds in dairy products by hollow-fibre liquid-phase microextraction coupled to liquid chromatography

In this work, the potential of a hollow-fibre liquid-phase microextraction (LPME)-based method has been studied and validated for the extraction of a group of nine oestrogenic compounds four of them being natural (oestriol, 17β-oestradiol, 17α-oestradiol and oestrone), four being synthetic (17α-ethynyloestradiol, diethylstilbestrol, dienestrol and hexestrol) and one metabolite (2-hydroxyoestradiol) in different dairy products (whole and skimmed natural yogurt, a probiotic yogurt-type drink and cheese). The methodology includes a prior protein precipitation with acidified acetonitrile for all samples and an additional defatting step with n-hexane for cheese, the matrix with the highest fat content. Later separation, determination and quantification were done by high-performance liquid chromatography coupled to a diode array detector and a fluorescence detector set in series. Calibration, sensitivity, precision and accuracy of the method were carried out in the selected matrices, providing good linearity, LODs in the low μg/kg or μg/L range, good precision and appropriate accuracy.