[Effects of temperature on the migration time window of micellar electrokinetic capillary chromatography]

The effects of capillary temperature, the nature and concentration of buffer on the migration time window of micellar electrokinetic capillary chromatography are investigated through three parameters including electroosmotic mobility (micro eo), the electrophoretic mobility micelle (micro ep,mc) and mobility ratio (Rm,mc). (micro eo) and (micro ep,mc) increase linearly as capillary temperature increases. Change in the viscosity of the running buffer is the main factor in the temperature effect. It is proved theoretically that the local viscosity at the capillary wall is different from the bulk viscosity. The increasing rate of micro eo with temperature is different from that of micro ep,mc. The migration time window can be expanded by lowering capillary temperature. Although the expanding is limited, this method can be very easily achieved on a commercial apparatus. A uniform formula has been derived to describe the relationships between micro eo, micro ep,mc and the concentration of buffer. For Tris and borate buffer, both micro eo and micro ep,mc decrease with increasing buffer concentration, but the decreasing rate is limited. Thus the effect on the migration time window is not significant. For phosphate buffer, the effects on micro eo and micro ep,mc are different in different concentration ranges. micro eo decreases rapidly in low concentration range but decreases slowly in high concentration range with increasing buffer concentration. micro ep,mc decreases in low concentration range but increases in high concentration range with increasing buffer concentration. The migration time window can be significantly expanded by increasing the concentration of phosphate buffer.