High-throughput and reliable determination of 13 haloacetic acids and dalapon in water and evaluation of control strategies

Abstract

A simple, fast, highly-sensitive and selective method for the determination of 13 HAAs and dalapon in water has been optimized and validated. The method is based on large volume injection (200 μL) and analyte determination with liquid chromatography coupled to negative electrospray ionization-high resolution mass spectrometry (LVI-LC-ESI(−)-HRMS). High throughput is possible due to minimum sample manipulation and short analysis time (16 min in total). This is the first analytical LC-MS-based method that covers the whole suite of HAAs for which analytical standards are available and dalapon, and thus, represents a less costly option than ion-chromatography-based technologies developed for the same purpose. The method provided satisfactory trueness (91–120%) and precision (<17%) values for all analytes, except for CAA. Matrix effects, always in the form of ionization suppression effects, were not relevant (<25%), except in the case of CAA, and they were all well compensated with the use of internal standard calibration. This methodology allows quantifying HAAs in tap waters at concentrations below 1 μg L⁻¹, except in the case of DBCAA and TCAA (3 μg L⁻¹) and CAA and DCBAA (6 μg L⁻¹). Thus, the presented analytical approach is satisfactory for the routine monitoring of HAA5 in drinking waters and obtaining additional knowledge on the formation and occurrence of other HAAs and dalapon that may be of relevance to ensure the provision of safe drinking water in the future. The concentrations of some of the brominated HAAs in chlorine-quenched disinfected water stored in the dark at −20 °C for seven days decreased between 26 and 46%, and thus, water samples should be analysed within 24 hours of their collection. As part of the validation method, the optimized approach was applied to evaluate two strategies to control HAA concentrations in water, i.e., lowering the water pH during the coagulation-flocculation step to improve process efficiency and using a household water pitcher filtration unit to remove HAAs in tap water.