Eluent and ligand effects in cation chromatography

Low-capacity surface-sulfonated cation exchange resins were prepared from high-performance gel beads of moderate cross- linking. Conditions necessary to control the reaction and obtain high efficiency cation-exchange material of a low-capacity were explored. Effects of reaction parameters on the depth and degree of sulfonation are discussed. An alternate method of determining total exchange capacity is also described;Selectivity of polyvalent metal cations versus hydrogen, sodium, magnesium, and ethylenediammonium cations is examined for the low-capacity sulfonated resins. Effects of complexing agents in the eluent are also examined for their effects on selectivity. Elution behavior with both complexing and non-complexing eluents are found to be predicted readily by use of the mass-action equilibrium expression for ion-exchange systems;The addition of complexing agents to the sample are shown to selectively complex certain metals as strong, stable complexes while leaving other metals essentially unbound. When injected, the masked ions do not compete for exchange sites on the column and are eluted in the void volume. The uncomplexed metal cations are chromatographed as usual. Analysis of alkaline earths in up to a 100-fold excess of interferent is carried out with reasonable recoveries;A method for speciation of iron by cation chromatography is described. Iron(II) is determined directly and iron(III) is detected after reduction to iron(II) just before injection. Choice of reducing agents and characteristics of the procedure are discussed. The;method shows favorable comparison to the spectrophotometric determination using 1,10-phenanthroline; (\u271)DOE Report IS-T 1170. This work was performed under Contract W-7405-Eng-82 with the Department of Energy