Separation and Direct Photometric Determination of Inorganic Anions by Capillary Zone Electrophoresis Using Suppressed Electroosmosis

A simple, sensitive and separative method for the photometric determination of inorganic anions was developed on the basis of suppressed electroosmosis by using a common silica capillary and a simple migrating solution. During the analysis of analyte anions by capillary zone electrophoresis, electroosmotic flow in a silica capillary was suppressed by using low-pH migrating solutions containing sodium sulfate. The stacking effect of sulfate ion was utilized for analyte concentration. Four kinds of inorganic analyte anions examined were detected in sharp signals, and the separation of a nitrate and a nitrite ion was improved by using the low-pH migrating solution with no decrease in detection sensitivity. Calibration graphs for nitrate and nitrite ions showed good linearity in the concentration ranges from about 10(-5) to 10(-4)mol dm(-3), with the detection limit for nitrate ion 4×10(-6)mol dm(-3). Separations of organic anions, such as aromatic sulfonate and carboxylate ions, were also examined; many of them were well separated by the proposed migrating solution. Those organic anions did not interfere with the determination of the inorganic anions.