Multiresidue screening of endocrine-disrupting chemicals and pharmaceuticals in aqueous samples by multi-stir bar sorptive extraction–single desorption–capillary gas chromatography/mass spectrometry

A multiresidue method for screening endocrine-disrupting chemicals (EDCs) and pharmaceuticals in aqueous samples is presented. Four 10-mL aliquots of water were taken for stir bar sorptive extraction (SBSE) and they were treated in the following way. In sample one, in situ derivatization was performed with acetic acid anhydride to improve the extraction efficiencies and chromatographic analysis of phenolic compounds. For the same reasons, aliquot two was treated with ethyl chloroformate to improve amine and acid extraction and analysis, and aliquot three with tetraethylborate to enhance organotin compound extraction and analysis. Methanol was added to sample four to stop adsorption of apolar solutes on the wall. After SBSE, the four stir bars, together with a plug of glass wool impregnated with bis(trimethylylsilyl)trifluoroacetamide (BSTFA) to derivatize hydroxyl functionalities, were introduced into the same thermal desorption tube, heat-desorbed, and analyzed simultaneously by capillary GC/MS. The figures of merit of the method were evaluated with an EDC model mixture. In scan-mode MS, the limits of detection (LODs) were in the range 1-500 ng/L, while the LODs dropped by a factor of 50-100 when ion monitoring MS was applied to the targets. The performance of the method was illustrated by analysing some real-world water samples.