In-port derivatization coupled to different extraction techniques for the determination of alkylphenols in environmental water samples

Abstract

Large volume injection (LVI)-in port silylation coupled to gas chromatography–mass spectrometry (GC–MS) for the determination of alkylphenols (APs) in water samples applying four different extraction approaches was evaluated. Among the variables studied for in-port derivatization, vent time, cryo-focusing temperature and the ratio solvent volume/N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) volume were optimized using an experimental design approach. Regarding the extraction techniques, different approaches previously optimized in the research group were tested. On the one hand different polymeric materials were tested: silicon rod (SR), polyethersulfone (PES) and polydimethylsiloxane (PDMS), the latter in the stir-bar sorptive extraction format (SBSE–PDMS). PES was chosen among the polymeric materials due to the higher recoveries (compared with SR) and lower price (compared to PDMS in the stir-bar sorptive extraction, SBSE–PDMS). Both MASE and PES protocols were selected at this point for further method validation and application to real samples. Finally, the developed methods were validated and applied to the determination of target analytes in various aqueous environmental matrices, including estuarine water and wastewater. Acceptable repeatability in the case of MASE (5–17%) and PES (7–21%) procedures and method detection limits (MDLs, 5–123 and 28–328ngL−1 for PES and MASE, respectively) were obtained for most analytes. In terms of apparent recoveries in the presence of matrix, estuarine and effluent samples showed no significant matrix effect (apparent recoveries in the 73–121% for PES and 74–128% for MASE), while a stronger matrix effect was observed for influent wastewater samples (98–132% for PES and 65–156% for MASE). Both MASE and PES extractions combined with LVI-in-port derivatization–GC–MS were applied to the determination of APs in the estuary of Bilbao (Gulf of Biscay, Spain).