Elution Behavior of Tungsten and Molybdenum in Ion Chromatography Using Organic Acid Eluents Having α-Hydroxyl Groups

Abstract

The ion chromatographic separation of W(VI) and Mo(VI) oxoanions was investigated by changing the eluents. Although W(VI) and Mo(VI) oxoanions were eluted with alkaline eluents over a pH range from 9 to 11, the separation factors between these oxoanions were not remarkably different, since W(VI) and Mo(VI) oxoanions were eluted as monomeric anions. On the other hand, the elutions of W(VI) and Mo(VI) oxoanions and the separation factors between these oxoanions were remarkably influenced within the pH range from 3 to 8. In particular, citric acid among α-hydroxy carboxylic acids was the most effective eluent for separating W(VI) and Mo(VI) oxoanions. In the use of eluents without α-hydroxyl groups, W(VI) and Mo(VI) oxoanions were strongly retained, due to the formation of W(VI) and Mo(VI) isopolyanions. The composition of W(VI)-citrate complex was 1:1.