Simultaneous determination of naturally occurring estrogens and mycoestrogens in milk by ultrahigh-performance liquid chromatography-tandem mass spectrometry analysis

A simple, fast, and reproducible method for the simultaneous determination of natural estrogens and mycoestrogens (resorcylic acid lactones) in milk by ultrahigh-performance liquid chromatography combined with electrospray ionization triple quadrupole tandem mass spectrometry (UHPLC/ESI-MS/MS) is described. The extraction was carried out by solid-phase extraction (SPE) using graphitized carbon black as solid sorbent. The use of carbon black allowed us to avoid any type of sample pretreatment, and the extraction was performed simply by diluting milk samples in water. Correlation coefficient values were obtained in the range between 0.9991 and 1, with good recoveries (67-107% at the lowest spiked level), repeatability (4.8-16.8%), and reproducibility (3.2-16.3%). Moreover, a very low matrix effect was observed for both estrogens and mycoestrogens. With respect to a previous method based on SPE with Oasis MAX cartridges, the one here described allowed us to detect all the analytes under investigation, at the lowest tested concentration level, including free estrogens (in particular estriol). Finally, the developed UHPLC/ESI-MS/MS method was applied to the analysis of some whole milk samples from different lactating animals (cow, goat, and donkey) as well as ultrahigh-temperature-treated cow milk and powder milk samples.