Automated solid-phase spectrophotometric system for optosensing of bromate in drinking waters

摘要

An automated method based on an optosensor included in a multisyringe flow injection system was developed for the determination of bromate in waters for human consumption. The optosensor was based on the formation of a colored radical cation after oxidation of chlorpromazine by bromate and its selective uptake in a mixed-mode cation exchanger sorbent (Discovery DSC-MCAX), placed on a flow-through spectrophotometric cell. In-line regeneration was attained by methanol + 5% (v/v) ammonia, fostering the application of the same sorbent portion up to 180 determinations. Parameters affecting the reaction development and uptake of the colored compound were studied and optimized, while in-line addition of sulfite (≥0.100 g L?1) prevented interference from hypochlorite. The proposed methodology allowed the determination of bromate up to 50.0 μg L?1, with 0.9 μg L?1 as the limit of detection, meeting the requirements of current EU and USA legislation. Application to real drinking water samples was successful, with a mean recovery of 100.2 ± 2.8% for spiked levels of 5.0, 10.0 and 25.0 μg L?1. Repeatability was good (RSD 3.6%, n = 10) with a determination throughput of 8 h?1, fostering the application to on-line control of water disinfection processes...