High-Performance Liquid Chromatographic Determination of Inorganic Anions by Using a Reversed-Phase Column as an Anion-Exchange Stationary Phase

We investigated the high-performance liquid chromatographic (HPLC) separation characteristics of bromide (Br(-)), nitrate (NO(3)(-)), iodide (I(-)) and thiocyanate (SCN(-)) on a Hydrosphere C18 column (150 x 4.6 mm i.d.) with 0.1 % aqueous phosphoric acid-acetonitrile elution and UV detection at 210 nm. The inorganic anions were retained and well separated on the column without using ion-pairing reagents. The retention of these inorganic anions increased with increasing acetonitrile concentration or decreasing phosphoric acid concentration. According to the evaluation of the basicity at the surface of the octadecylsilica packing material of Hydrosphere C18, we concluded that the inorganic anions were retained on the column by an anion-exchange interaction. We investigated the determination of Br(-), I(-) and SCN(-) with a mobile phase consisting of 0.1 % phosphoric acid-acetonitrile (80 : 20, v/v) and a 10-mu L injection at a flow-rate of 1.00 mL min(-1). The calibration curves for the inorganic anions were linear over the concentration range of 1.0 x 10(-6)-5.0 x 10(-4) M. The detection limits (S/N = 3) for Br(-), I(-) and SCN(-) were 2.5 x 10(-7), 0.9 x 10(-7) and 2.4 x 10(-7) M, respectively. We applied this method for an investigation of inorganic anion transmission through ultrafiltration membranes.