HIGH TEMPORAL RESOLUTION MONITORING OF GLUTAMATE AND ASPARTATE IN-VIVO USING MICRODIALYSIS ONLINE WITH CAPILLARY ELECTROPHORESIS WITH LASER-INDUCED FLUORESCENCE DETECTION

An automated method for high temporal resolution monitoring of the neu rotransmitters glutamate and aspartate in vivo using capillary electro phoresis (CE) with laser-induced fluorescence (LIF) detection was deve loped. Microdialysis probes placed in the striatum of anesthetized rat s were coupled on-line with the CE system by an automated flow-gated i nterface. Analytes were derivatized on-line with o-phthaldialdehyde/be ta-mercaptoethanol and detected by LIF using the 354 nm line (7 mW) of a He-Cd laser for excitation. With dialysis now rates of 1.2 mu L/min , the detection limit at the dialysis probe was 200 nM for glutamate a nd aspartate. Glutamate and aspartate could be resolved in less than 5 s with over 200 000 theoretical plates. The sampling time was limited by the separation time while the temporal resolution was limited to s imilar to 12 s because of band broadening that occurs within the probe and its associated tubing. The high temporal resolution allowed the f irst simultaneous monitoring of glutamate and aspartate overflow durin g acute electrical stimulation in the rat brain.