QUANTITATIVE INJECTION FROM A MICROLOOP - REPRODUCIBLE VOLUMETRIC SAMPLE INTRODUCTION IN CAPILLARY ZONE ELECTROPHORESIS

A wire loop deployed at the tip of a capillary electrophoresis system has been investigated as a means of quantitative injection. A thin fil m of a liquid is formed on the loop, the loop is transferred to a seal ed chamber, and then pneumatic pressure is applied to introduce the co ntents of the loop into the capillary. As long as the applied pressure is below a certain threshold, no air is introduced into the capillary , even after the loop contents have been fully introduced. Sample surf ace tension and viscosity do not have a significant effect on the inje cted volume. The small loop injection technique appears to be a robust and reproducible alternative to presently practiced approaches to sam ple injection in CE.