Development and application of diffusive gradients in thin-films for in situ sampling of the bitterest chemical-denatonium benzoate in waters

Denatonium benzoate (DB), a commonly used bitter agent in numerous products, has recently been recognized as a waterborne contaminant due to concern about its potential persistence, mobility and toxicity (PMT). However, its occurrence, levels and fate in global aquatic environments are largely unknown. In this study, a new sampling method, based on diffusive gradients in thin films (DGT) with mixed-mode cation exchange (MCX) as the binding agent, was developed for measuring DB in waters. MCX shows a rapid adsorption and high capacity for DB. DB is linearly accumulated by MCX-DGT. pH (6-8), ionic strength (0.01-0.5 M), or DOM (0-10 M) do not show any significant effect on the MCX-DGT performance, confirming its reliability. The DGT measurements in a wastewater treatment plant (WWTP) are comparable to those by paralleled grab sampling. The field results suggest DB is persistent in WWTPs and could be a potential domestic wastewater indicator. Therefore, MCX-DGT is a promising technique for understanding the environmental occurrence, levels and fate of DB. This is a first report of using DGT for DB monitoring and of DB occurrence in Chinese environments. Further exploration of DGT as a reliable passive monitoring tool for a wide range of PMT substances in different applications is warranted.