| Abstract
| - An approach to capillary electrophoresis with electrochemical detection (CE-EC) suitable for determination ofdopamine in 1-min brain microdialysate samples isdescribed. The CE-EC system includes an electrochemicaldetection cell that permits easy, precise, and permanentalignment of a carbon fiber microelectrode with a separation capillary (30-μm i.d., 75-cm length). Amperometricdetection was performed at a constant applied potentialof 600 mV with respect to a Ag/AgCl reference electrode.Decoupling of the electrophoretic current from the amperometric detector was accomplished with an integratedend-column decoupler prepared by etching the capillaryoutlet with HF. The decoupler produces baseline noiseof 50 fA, or less, in the presence of 10−20-μA current inthe separation capillary. The low baseline noise affordslow mass (attomoles) and low concentration (nanomolar)detection limits for dopamine and 4-methylcatechol. Apeak attributable to dopamine was identified in electropherograms of brain microdialysate samples obtainedfrom anesthetized rats. Identification of the dopaminepeak was confirmed by pharmacological methods. Dopamine was readily detected in 1-min brain microdialysatesamples. The dopamine concentration in 1-min brainmicrodialysis samples was significantly altered by drugtreatments and by brief electrical stimulation of dopaminergic axons.
|
