Dynamic and Fixed-Site Ion-Exchange Columns with Conductometric Detection for the Separation of Inorganic Anions

Abstract

The reproducibility and stability of ion exchangers formed by sorption of modifiers onto reversed phases by a dynamic-equilibration procedure have been examined. Repeated coatings gave retention times constant to <2%, even between two different columns, and the exchange capacity was constant for at least 40 I of eluent. Column efficiencies were determined for a high-performance column and several reversed-phase systems in both suppressed and unsuppressed modes; the reversed phases were operated in dynamic-equilibration and permanently coated modes. The sensitivities of the different column systems were compared under controlled conditions and, with proper attention to temperature effects, peak-to-peak background noise could be reduced to 0.005μs/cm. Detection limits (twice peak-to-peak noise) for both suppressed and non-suppressed modes were as low as 1 to 5 ng/ml for 100-μ1 injections. No column system had a definite advantage in all analysis situations, and some of the major positive and negative features of each system are outlined briefly.