ION-CHROMATOGRAPHIC DETERMINATION OF MICRO-AMOUNTS OF SULFATE ION USING A CHITOSAN LOADED COLUMN

Chitosan, which is protonated in acidic medium and thus acts as an anion exchanger, is used as an adsorbent for anionic metal complexes. Good separation of sulfate ion from matrix ions in natural water samples was achieved by elution with 4.0 mM phthalic acid (adjusted to pH 4.1 using 0.1 M tris-hydroxymethyl-aminomethane) in an ion chromatographic system using a chitosan beads loaded column (Shodex CHITOpak KQ 800P or Fujiboseki CHITOpak GPC 7000 KQ-800-5). In this procedure, the determination and separation of sulfate ion was not influenced by the presence of 1500 ppm chloride ions. The mobile phase flowed at a rate of 1.0 ml/min and the electro-conductivity detector was used at 45 degrees C. When 100 mu l of sample solution was injected, the calibration curve was linear below 100 ppm (coefficient of correlation 0.999) and the observed detection limit at S/N=2 was 0.18 ppm for sulfate ion. The relative standard deviations of seven measurements for the determination of sulfate ion in sea- and lake-water samples were in the range of 0.21 similar to 2.4%. The proposed method proved to be applicable to the determination of sulfate ion in natural water samples.