Fast derivatization procedure for the analysis of phytoestrogens in soy milk by gas chromatography tandem mass spectrometry

In this work an optimized GC–MS/MS method, based on a simple and fast derivatization procedure, is proposed for the determination of five phytoestrogens (formononetin, daidzein, coumestrol, genistein and biochanin A) in soy milk. A systematic study of the instrumental analysis conditions was carried out, optimizing different MS acquisition parameters. At the same time, the derivatization procedure was optimized testing three silylating reagents. The results showed the independence of the derivatization efficiency from the heating treatment applied before analysis, enabling the derivatization directly in the injection port; moreover, the use of a temperature programmed injection enhanced sensitivity and precision of the analysis. The described optimization steps allowed a significant gain in the sensitivity of the overall method, leading to detection limits of 0.1–17.7 μg L− 1, which are lower or comparable to values reported in the literature for GC–MS analysis of these analytes. The method was tested on some soy milk samples from the Italian market, proving its suitability for the analysis of phytoestrogens in this complex matrix.