DETERMINATION OF AMMONIUM AND OTHER MAJOR CATIONS IN RIVER AND RAIN WATER BY ION CHROMATOGRAPHY USING SILICA-GEL AS AN ION-EXCHANGER

The separation of NH4+ from Na+, K+, Mg2+ and Ca2+ on silica gel columns was investigated using natural water samples and lithium oxalate as a retention modifier. The pore size of silica gels was found to be the most important factor affecting the retention of the cations. When a 0.0025 mol dm-3 lithium oxalate solution of pH 7 was used as the mobile phase these cations could be completely separated on a short silica-gel column (Develosil 30-3, 35 mm×4.0 mm i.d.) within about 20min. NH4+ contents in river (0.01 -0.27ppm) and rain (1-1.8ppm) water samples were determined successfully. © 1990, The Japan Society for Analytical Chemistry. All rights reserved.