Markedly Enhanced Purge‐and‐Trap Performance and Efficiency for the Determination of Ammonium Ion in High‐Salinity Water Samples

We have previously developed a purge‐and‐trap (P&T) preconcentrator, useful for the determination of trace amounts of ammonium ion in high‐salinity water samples by ion chromatography (IC). In this study, we succeeded in improving the P&T system to markedly enhance performance and efficiency for the determination of ammonium in high‐salinity water samples. Compared to the previous work, the background signal was reduced by a factor of 9. The maximum overall collection efficiency increased greatly from 64% to 97%. With the modified P&T system, this method can be applied to a wide ammonium concentration range of 5 orders of magnitude. These were attributed to the substitution of polypropylene vessels for glass ones, the improvement of the gastight of the P&T system, the increase of the liquid depth in the purge vessel, and the use of 10 mM sulfuric acid as the trapping solution for high ammonium concentration samples. Interferences of 20 native amino acids to the ammonium determination are slightly positive, but also negligible except asparagine and glutamine. The proposed method has been successfully applied to the accurate determination of wide levels of ammonium in seawater and sweat samples.