Ion chromatographic determination of nitrate and sulfate in natural waters containing humic substances.

Abstract

In the study of the pollution of natural waters, the concentrations of nitrate and sulfate are important factors. The analytical methods use for nitrates and sulfates are to varying extents influenced by the presence of humic substances in natural waters. Determinations of anions in natural waters by various methods, including ion chromatography, are disturbed by the inevitable presence of humic substances. A cleanup column, packed with chemically bonded amine material for HPLC, is useful for the selective removal of disturbing humic substances prior to anion analysis by ion chromatography. For all the development work described, the same separation column is used. No change was noted in color of the resin nor any deterioration of the chromatographic properties after more than 500 injections and thus it was concluded that the separation column was effectively protected from the disturbing fraction of humic acid. A technique similar to the one described probably can be used to discriminate metal ions associated with humic substances from free metal ions. 14 references, 2 figures, 3 tables.