OPTIMIZATION OF THE ANION-EXCHANGE SEPARATION OF METAL-OXALATE COMPLEXES

Anion exchangers, prepared by the sorption of cetylpyridinium chloride onto a reversed phase, have been evaluated for the separation of the transition metal ions Mn2+, Co2+, Ni2+, CU2+, and Zn2+. Parameters examined included nature of complexing reagent, eluent pH, eluent concentration, speciation of the metal ion in the complexation system, and column capacity. The separations obtained with an oxalate eluent were compared to those obtained with a cation exchanger prepared by the addition of n-octanesulfonate to the eluent. Theoretical prate heights were in the range of 0.010 mm to 0.025 mm, and were in many instances, slightly better than those obtained with cation separation systems. Metal ion speciation in the eluent appeared to be a dominant factor determining the efficiency of the anion separation; metal ions with one dominant complexed ion generally gave more efficient separations. Compared to cation separations, analysis times were similar, but separation selectivities were considerably different.