Separation of acidic compounds by strong anion-exchange capillary electrochromatography

Separation of the acidic compounds in the ion-exchange capillary electrochr omatograph (IE-CEC) with strong anion-exchange packing as the stationary ph ase was studied. It was observed that the electroosmotic flow (EOF) in stro ng anion-exchange CEC moderately changed with increase of the eluent ionic strength and decrease of the eluent pH, but the acetonitrile concentration in the eluent had almost no effect on the EOF. The EOF in Strong anion-exch ange CEC with eluent of low pH value was much larger than that in RP-CEC wi th Spherisorb-ODS as the stationary phase. The retention of acidic compound s on the strong anion-exchange packing was relatively weak due to only part ial ionization of them, and both chromatographic and electrophoretic proces ses contributed to separation. It was observed that the retention values of acidic compounds decreased with the increase of phosphate buffer and aceto nitrile concentration in the eluent as well as the decrease of the applied voltage, and even the acidic compounds could elute before the void time. Th ese factors also made an important contribution to the separation selectivi ty for tested acidic compounds, which could be separated rapidly with high column efficiency of more than 220 000 plates/m under the optimized separat ion conditions. (C) 2000 Elsevier Science BN. All rights reserved.