Ultra-violet visualization of inorganic anions by reversed-phase ion-interaction chromatography; factors that control retention and selectivity

Abstract

This paper describes the development and characterization of a separation and detection system for the analysis of mixtures of UV-transparent inorganic anions. Retention and separation occurs when a hydrophobic, positively charged paired-ion chromatography (PIC) reagent or an ion-interaction reagent (IIR) is added to the mobile phase of a reversed-phase system. Detection of UV-transparent ions results from a perturbation of the distribution equilibria of the UV-absorbing IIR upon injection of the sample ions. The effect of factors such as the concentration and nature of the buffer, co-ions and IIR as well as an organic modifier are described. The major advantages of this method are that the system is nearly completely nonspecific, the separation system takes advantage of highly efficient reversed-phase columns, rapid separations of 4–6 anions in approximately 6–7 min and good sensitivity with detection limits of less than 1 nmole injected. In addition, no special equipment is required to perform ion analysis by this technique. Only conventional high-performance liquid chromatography pumps, detectors and reversed-phase columns are required.