Determination of tungstate in soils and sludges by using single-column ion chromatography

A procedure has been developed for the determination of tungstate at trace levels in aqueous extracts of soil and sludge by single-column ion chromatography (SCIC). Chromatographic parameters based on ion selectivity, time of determination and signal response were optimized for tungstate with the simultaneous detection of nitrate and sulfate. Chloride, phosphate, chromate, molybdate and vanadate were found not to interfere in the determination. A low-capacity resin-based column was used for the separation with p-hydroxybenzoic acid (5 mM) at pH 8.5 as the eluent. The limit of detection defined as three times the signal-to-noise ratio was 170 μg l^?1 (2-ml sample). The resolution between tungstate and sulfate was R_s=2.84. The results for aqueous extracts agree closely with those obtained by an accepted spectrophotometric method.