SAMPLE STACKING OF AN EXTREMELY LARGE INJECTION VOLUME IN HIGH-PERFORMANCE CAPILLARY ELECTROPHORESIS

Sample stacking is a simple on-column concentration technique in high-performance capillary electrophoresis (HPCE). However, the amount of sample which can be loaded into the column in conventional sample stacking is rather limited because of disturbances caused by the low-concentration sample buffer. This report describes a technique of stacking an extremely large sample volume into narrow bands. The technique is based on the principal that the local electrophoretic velocity of the ions inside the sample buffer is much faster than the bulk electroosmotic velocity of the solution By applying a high voltage with reversed polarity immediately after loading the sample, one can remove the sample buffer prior to separation of analytes. Since the peak-broadening mechanism is removed from the system, better resolution can be achieved for a large sample volume. Since large amounts of sample can be loaded onto the column, a factor of several hundreds in signal enhancement is obtained