Capillary electrophoresis of glutamate and aspartate in rat brain dialysate. Improvements in detection and analysis...

Addition of cyclodextrins (CDs) to the electrolyte buffer in the capillary zone electrophoresis (CZE) separation of derivatized amino acids was evaluated in terms of fluorescence signal enhancement, resolution, and migration time effects. Maximum fluorescence signal enhancement was observed with separation buffers containing 4 mM beta-cyclodextrin or 10 mM hydroxypropyl beta-cyclodextrin. Resolution values decreased as the CD concentrations increased. Migration times were dependent on CD concentration. Inclusion complex formation constants calculated using changes in migration time showed slight agreement with those calculated by the steady-state fluorescence enhancement technique. Analysis of 20 microl of rat brain microdialysate by CZE using 4 mM beta-cyclodextrin in borate buffer resulted in baseline resolution of glutamate and aspartate in 3.6 min. The results of this work indicate that, when used as separation buffer additives, cyclodextrins are capable of increasing the fluorescence signal and decreasing the migration times of NDA-derivatized acidic amino acids.