The influence of experimental conditions and of organic solvents as modifiers on the separation of metallothionein isoforms by capillary zone electrophoresis in an uncoated capillary column

Abstract

Putative metallothionein (MT) isoforms are readily separated by capillary zone electrophoresis (CZE) with a mixture of tris(hydroxymethyl)aminomethane (Tris) and borate buffers in uncoated polyimide-cladded fused-silica capillary tubing. The influence of buffer concentration and composition, pH, running voltage and temperature on the electroosmotic mobility and on the electrophoretic mobilities of model samples (rabbit liver and horse kidney MT) have been investigated. The use of organic solvents as buffer modifiers and their effect on the separation of putative metallothionein isoforms is also described. It is shown that organic solvent modification significantly enhances the resolution—with organic solvents as modifiers it is possible to obtain a good separation of putative isoforms of rabbit liver MT in one run whereas two separate runs were needed at different pHs or at different temperatures when the separation was performed with Tris-borate buffer without organic-solvents as modifiers were found to be solventspecific although the trends were in the same direction (i.e. decreasing electroosmotic mobility with increasing percentage of organic solvent). Differences in effect on individual putative MT isoforms were observed, indicative of different chemical and physical characteristics of the isoforms. A difference in polymorphism of horse kidney MT and rabbit liver MT is clearly apparent.