ONLINE INTERFACE BETWEEN MICRODIALYSIS AND CAPILLARY ZONE ELECTROPHORESIS

A now-gated, on-line interface between a microdialysis sampling probe and capillary zone electrophoresis with UV absorption detection was ch aracterized and applied. Electrophoresis conditions were chosen so tha t ascorbic acid migrated in 42-100 s with 65 000-120 000 theoretical p lates. These results were obtained using a 25 mu m inner diameter capi llary with an inlet to detector length of 15 cm and electric field str ength of 400-600 V cm(-1). Theoretical plates, migration times, and pe ak areas for ascorbic acid injected on-line from the interface were th e same as those obtained for off-line injections. The system allowed s tep changes in ascorbic acid concentration to be followed with 85 s ti me resolution when the dialysis now-rate was 79 nl min(-1). The time r esolution was improved to 65 s when the dialysis flow-rate was 155 nl min(-1). The relative standard deviation for peak heights was 3.8% and a linear response over the physiologically relevant range for ascorbi c acid was observed. At 79 nl min(-1) the relative recovery of the pro be was 98%. The high relative recoveries improved detection limits, si mplified quantification, and resulted in decreased disturbance to the system being studied when compared to the more conventional dialysis f low-rates of 0.5-1 mu l min(-1). As a demonstration of the system, asc orbic acid in the caudate nucleus of rat brain was detected and monito red in response to systemic amphetamine injections and anaesthetic ove rdoses. This system is the first to demonstrate high relative recoveri es and high time resolution simultaneously with microdialysis sampling .