A novel automated method for the quantification of ten halobenzoquinones in drinking water using online solid-phase extraction coupled with liquid chromatography tandem mass spectrometry

Abstract

When assessing occurrence and exposure to toxic chemicals in drinking water, developing methods that are sensitive and efficient is paramount. A new method was developed for the quantification of ten halobenzoquinones (HBQs), a class of disinfection by-products (DBPs) in drinking water, which have been shown to be more toxic than most regulated DBPs. This method uses a small sample volume with online solid phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Previous methods used offline SPE coupled with standard addition, and a pre-concentration step. This requires larger volumes of sample, solvent, and standards. The current method has comparable limits of quantification (0.2–166 ng/L), requires minimal sample preparation, and analysis is almost entirely automated. It also includes 2,6-dibromo-3‑chloro-5-methyl-1,4-benzoquinone which was not included in previous methods. A stability test was conducted over a one-week period with different preservatives, including ascorbic acid, sodium thiosulfate, and formic acid. Method optimization included source temperature, SPE size, sample volume, and SPE loading time. This method was validated using drinking water collected from four different drinking water plants; spike recoveries of HBQs were between 70–111%, relative standard deviations of <20%, and linearity of >0.98. Further, using this method, we report the highest concentration of 2,6-dibromo-1,4-benzoquinone found in drinking water (254 ng/L).