Development of a solid-phase extraction liquid chromatography tandem mass spectrometry method for benzotriazoles and benzothiazoles in wastewater and recycled water

Two methods employing solid-phase extraction and liquid chromatography tandem mass spectrometry were developed for the analysis of benzotriazoles (BTs) and benzothiazoles (BThs), compounds which are commonly found in a large variety of commercial and household products. The first method was able to detect 7 BTs and 7 BThs, the largest suite of BTs and BThs analysed in a single method to-date, but could not distinguish between the isomers, 4-methylbenzotriazole (4-MeBT) and 5-methylbenzotriazole (5-MeBT). Therefore, a second method was developed to achieve the chromatographic separation of 4-MeBT and 5-MeBT. The methods were validated for ultrapure water and secondary wastewater, and method limits of detection (MLD) for BTs and BThs (for the primary method) ranged from 0.1 to 58 ng L−1 for ultrapure water, and 2 to 322 ng L−1 for secondary wastewater. For the secondary method, MLDs for 4- and 5-MeBT ranged from 8 to 12 ng L−1 for ultrapure water, and 388 to 406 ng L−1 for secondary wastewater. Analysis of secondary wastewater and reverse osmosis (RO) treated water from an advanced water recycling plant in Australia is presented, and represents the first reported data from the analysis of BTs and BThs in recycled water. Some of these compounds were found to persist through wastewater treatment and incompletely removed by RO treatment. Benzotriazole (BT), 4-MeBT, 5-MeBT and 2-(methylthio)benzothiazole were detected in secondary wastewater, however the latter compound was not quantifiable. Concentrations of BT and tolyltriazoles (TTs, i.e. sum of 4- and 5-MeBT, detected with the primary method) in secondary wastewater were 3.3 (±0.02) and 2.8 (±0.04) μg L−1, respectively. These same compounds were also detected in the post-RO water samples at concentrations of 974 (±28) ng L−1 for BT and 416 (±34) ng L−1 for TTs. 2-Hydroxybenzothiazole was also detected in the post-RO water samples, however it was not quantifiable. Removal efficiencies for RO treatment were calculated to be between 70% and 85% for BT and TTs.