A validated reverse-phase LC-MS/MS method for the analysis of haloacetic acids in drinking water: supporting the transition from HAA5 to HAA9

Haloacetic acids (HAAs) are potentially toxic by-products formed from interactions of organic matter and chlorine during disinfection of drinking water, with brominated HAAs forming when bromide is present. Some countries require monitoring of drinking water for five HAAs, but there is an increasing health concern related to the more toxic brominated HAAs and monitoring of nine HAAs (HAA9) is becoming more widespread. However, existing methods of analysis for HAA9 are often sub-optimal, involving complex derivatisation steps and/or long analytical run times. This article presents an improved methodology utilising reverse-phase LC-MS/MS for which sample preparation involves only simple pH adjustment and the analytical run takes 10 min. The efficacy of the method has been demonstrated by a full validation across four drinking water matrices with good sensitivity (<0.8 μg/L), precision (<7%), and bias (<10%) observed for HAA9. A direct comparison using real tap water samples was performed against the widely used existing gas chromatography electron capture the detection method. The new LC-MS/MS method was significantly quicker and easier and demonstrated improved performance in terms of accuracy and precision. This has implications for understanding the risk posed by HAAs in chlorinated water by eliminating the possible historical underestimates of the levels of the more toxic brominated compounds.