Characterization of ion chromatography columns based on hydrophobicity and hydroxide eluent strength.

Only a few systematic studies have been performed on the factors affecting retention and selectivity in modern ion chromatography. In this study retention and selectivity of Dionex AS10, AS11-HC, AS15, AS16, AS18, AS19, AS20 and AS24 anion exchange columns with hydroxide eluent were studied using the Virtual Column Separation Simulator database. The hydrophobicity and hydroxide eluent strength on each of the columns were quantified. The hydrophobicity measured based on retention of the homologous series of alkyl sulfonates (H(RSO3(-)) do not correlate with the hydrophobicities quoted by the manufacturer (H(Dionex)). Rather the H(Dionex) reflect the strength of hydroxide as an eluent on these columns. The relative eluent strength of hydroxide (K(OH−,A) on commercial Dionex IC columns were calculated vs. four reference ions. The (K(OH−,Cl-) range from 0.32 (AS10) to 7.3 (AS16), with a ranked order of AS10≪AS15≪AS19<AS24<AS18<AS11-HC≈AS20<AS16. Column selectivity for the inorganic anions is reflected by the behaviour of the halides but does not correlate with either the hydrophobic retention of the alkyl sulfonates (H(RSO3(-))or hydroxide eluent strength (K(OH−,A) of the columns. Column selectivity for organic monovalent anions correlates with the H(RSO3(-) on the IC columns.