Development of Analytical Method for Ammonium Nitrogen by Continuous Flow Analysis Using a Gas Separator

In order to establish a quick and simple analytical method for ammonium nitrogen without using phenol, which is a harmful substance, we developed a method involving continuous flow analysis （CFA）. To prevent interference by metal ions in the sample, ethylenediaminetetraacetic acid （EDTA） was added to the flow. A gas separator using a PTFE membrane filter was used to prevent EDTA interfering with the coloring mechanism and to avoid the effects of foreign substances on the measurement. Only ammonia in the sample is separated by the gas separator in the form of gaseous ammonia and is measured by the salicylic acid indophenol method; this enables analysis without using phenol, and with less susceptibility to inhibiting substances. Both this method and the conventional method using phenol were used to measure samples including seawater and industrial wastewater, and equivalent results were obtained. An evaluation of the method itself confirmed that there was no significant difference from the conventional method. These results suggest that our method offers the same measurement performance as the conventional method and can replace it.