Precipitating halides by silver carbonate: A facile pretreatment method to enable total organic halogen analysis in water

Total organic halogen (TOX) analysis is essential to monitor the formation of all halogenated organics in water. Currently, TOX needs to be separated by tailored activated carbon and then converted by combustion before determination, which have some inherent drawbacks and multiple complicated phase transition processes that prevent its widespread application. To overcome these issues, this study proposed a facile alternative TOX analytical method based on a fundamental water chemistry principle. That is, silver carbonate was used to remove halides from water firstly by forming silver halides precipitates, and then TOX remaining in water was dehalogenated by vacuum ultraviolet photolysis before determination of TOX by ion chromatography. Since the keys to success for the proposed approach are to maximize the removal of halides and to minimize the loss of TOX in water, a series of operation variables were evaluated and optimized. Under optimal conditions, the residual Cl^– and Br^– levels in treated water were less than 57.5 μg-Cl/L and 42.7 μg-Br/L, respectively. Meanwhile, the method achieved satisfactory recoveries of model organic halogen compounds (30.0–1000.0 μg/L) in both synthetic water (92.0–101.0 %) and tap water (98.0–103.6 %). Because this method uses only inexpensive reagents and handy operations without any phrase-changing for target analyte, it may serve as a routine means for detecting TOX in the future.