ONLINE SAMPLE PRECONCENTRATION ON A PACKED-INLET CAPILLARY FOR IMPROVING THE SENSITIVITY OF CAPILLARY ELECTROPHORETIC ANALYSIS OF PHARMACEUTICALS

An on-line preconcentration method is reported that improves the sensitivity of capillary electrophoretic analyses by at least two orders of magnitude. The method uses a concentrator capillary with a 75 mum I.D. and a 1-mm length packed bed at the inlet end that can concentrate samples using the principles of liquid chromatography. Using low-molecular-mass pharmaceutical standards as examples, the parameters used in developing a preconcentration sensitivity enhancement method were optimized. The optimized method was then used to evaluate the quantitative aspects of capillaries of this type, including run to run and capillary to capillary reproducibility, linearity, and efficiency and resolution. In addition, the analysis of a urine sample spiked with doxepin at the 500 ppb level is reported.