Comparative study of the determination of peroxomonosulfate, in the presence of other oxidants, by capillary zone electrophoresis, ion chromatography, and photometry

Abstract

Several methods for quantitative determination of peroxomonosulfate in detergents, in the presence of other oxidants, have been investigated. The photometric technique applied was based on the well-known starch–iodine reaction. The oxidizing agent was quantified by determining the amount of iodine produced. The influence of other oxidants present was examined. Ion analysis was performed by capillary zone electrophoresis (CZE) and ion chromatography (IC). Because peroxomonosulfate in detergents is always accompanied by sulfate, the main goal was to separate the sulfur species without causing the decomposition of the unstable peroxomonosulfate ion. The sulfur species could be separated within less than 4 min by CZE with a pyromellitic acid electrolyte at pH 3.5 to 5.0. Sulfate and peroxomonosulfate were separated by IC within 11 min by use of a phthalic acid mobile phase at pH 3.0. The peroxomonosulfate content was determined by calibration. The calibration plot was linear from 5 to 50 µg mL^–1 SO₅ ^2– for IC and from 7.3 to 182.3 µg mL^–1 SO₅ ^2– (corresponding to 20 to 500 µg mL^–1 triple salt) for CZE.