Determination of ammonium ion in biological nitrification-denitrification process water by ion exclusion chromatography with ion exchange enhancement of conductivity detection.

Abstract

Ammonium ion in biological nitrification-denitrification process with batchwise treatment was determined by ion exclusion chromatography using water as an eluent with ion exchange enhancement of conductivity. Ammonium ion was selectively separated by ion exclusion from alkali metal and alkaline earth metal cations. The detection sensitivity of the ammonium ion was improved about 11-fold with two ion exchange enhancement columns inserted in series between the separation column packed with OH^--form anion-exchange resin and the detector. The first enhancement column packed with Cl^--form anion-exchange resin converts ammonium hydroxide to ammonium chloride and the second enhancement column packed with H⁺-form cation-exchange resin converts ammonium chloride to hydrogen chloride of much higher limiting equivalent conductivity. The calibration curve of ammonium ion detected as hydrogen chloride was linear over the concentration range of 10 to 100 ppm. The method provides a fast, selective, and sensitivity way to determine the ammonium ion in biological nitrification-denitrification process water.