Packing procedures for high efficiency, short ion-exchange columns for rapid separation of inorganic anions

An optimised packing procedure for the production of high efficiency, short, particle-packed ion-exchange columns is reported. Slurry-packing techniques were applied to a series of interconnected short columns, with the columns situated intermediate between the inlet and outlet ends of the series being used for separations. The fast separation and determination of inorganic anions was achieved using short (4 mm ID, 30 mm long) columns packed with Dionex AS20 high-capacity anion-exchange stationary phase. Seven inorganic anions (bromate, chloride, chlorate, nitrate, sulfate, chromate and perchlorate) are separated in 2.6 min using a hydroxide gradient and a flow-rate of 1.8 mL/min (total analysis time including re-equilibration was 3.5 min). Under isocratic conditions, the home-packed columns exhibited efficiency values of 43,000 N/m for chloride at a flow-rate of 0.3 mL/min, compared to 54,000 N/m for a commercial 250 mm AS20 column at the same flow-rate. However, the short columns gave approximately a threefold higher sample throughput. The short, home-packed columns could be produced reproducibly and gave consistent performance over extended periods of usage.