Metal ion capillary electrophoresis with direct UV detection effect of a charged surfactant on the migration behaviour of metal chelates

Abstract

The migration behaviour of anionic metal 4-(2-pyridylazo)resorcinol (PAR) and Arsenazo III complexes was investigated in capillary electrophoresis (CE) using micellar solutions of sodium dodecyl sulphate. The separation mechanism of arsenazo complexes is governed by the electrophoresis in the bulk carrier electrolyte without any observable interaction with the micellar phase. For less hydrophilic PAR complexes, the resolution can be additionally explained in terms of differential partitioning into the micelle. It was also found that ion-pair formation between anionic solutes and the cationic component of the electrophoretic buffer contributes to the retention mechanism and permits the separation of closely migrating PAR complexes. Both chelating systems have been applied to the CE separation and determination of various metal ions with enhanced selectivity and sensitivity relative to previously reported metal complexation CE techniques. Application to the analysis of complex sample matrices, containing high levels of acids and complexing agents, was demonstrated.