Alkanesulfonate homologous series as eluent components in anion chromatography Novel eluent selection system for monovalent analytes

Abstract

Common inorganic anions can be separated on an anion-exchange column of low capacity using a very dilute solution of alkanesulfonate as eluent components and a conductivity detector. A mathematical relationship has been found between the retention volumes of monovalent analyte using different alkanesulfonates as eluents and quaternary ammonium functionalized styrene-divinylbenzene stationary phase. Retention volumes decrease steadily for the homologous series of alkanesulfonates (methane-, ethane-, propane-, butane- and pentanesulfonates) as the alkyl-chain length increases. This system made it possible to establish the ion-exchange capacity of the separation column and the inter-eluent selectivity coefficients and permitted prediction of retention volume with variation of type and concentration of eluent. The parameters of retention model can be readily derived from elution experiments. The eluent system has been used easily to design separation schemes. Good agreement was obtained between the observed and predicted values for the anions of practical interest (fluoride, chloride, chlorate, nitrite, nitrate, bromide, bromate). Retention of ions can be manipulated by changing either the concentration or carbon number of the alkanesulfonate eluent from homologous series. The response of analyte retention to changing eluent conditions can be illustrated with a retention nomogram.