Determination of Alternaria toxins in drinking water by ultra-performance liquid chromatography tandem mass spectrometry.

A sensitive and reliable analytical method has been developed and validated for the determination of five Alternaria toxins, including tenuazonic acid (TeA), alternariol (AOH), alternariol monomethyl ether (AME), altenuene (ALT), and tentoxin (TEN), in drinking water using a one-step enrichment and clean-up strategy followed by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Drinking water samples were preprocessed using excess sodium sulfite to remove residual chlorine, and the pH was adjusted by formic acid. Analytes were concentrated and purified from the water samples using hydrophilic-lipophilic balanced (HLB) solid-phase extraction (SPE) cartridges. Chromatographic separation was performed on an Acquity HSS C column using 0.1 mM ammonium carbonate and methanol as the mobile phase. The average recoveries at three spiked levels (0.1, 0.5, and 1 ng/L for TeA, AOH, and ALT; 0.01, 0.05, and 0.1 ng/L for TEN and AME) were 76.1-106.5%, with an intra-day precision less than 15.5% and inter-day precision of 11.8-16.5%. The limits of detection (LODs) were 0.05 ng/L for TeA, AOH, and ALT and 0.005 ng/L for TEN and AME. The limits of quantification (LOQs) were 0.1 ng/L for TeA, AOH, and ALT and 0.01 ng/L for TEN and AME. The developed method was applied to monitor 289 drinking water samples collected in Beijing from 2015 to 2017, and TeA and TEN were found in 28 samples, with concentrations ranging from 0.16 to 2.7 ng/L and 0.21 to 2.2 ng/L, respectively.