Rapid determination of aspartate enantiomers in tissue samples by microdialysis coupled on-line with capillary electrophoresis

Microdialysis was coupled on-line with derivatization by o-phthalaldehyde a nd beta-mercaptoethanol and optically gated capillary electrophoresis to de termine D- and L-aspartate in tissue samples obtained from rats. The microd ialysis probe was inserted into a homogenized tissue sample which allowed g eneration of a continuous sample stream that was filtered and deproteinated . With 7.5 mM beta-cyclodextrin (CD) in the electrophoresis buffer, the ena ntiomers of interest could be resolved in 3 s with an electric field of 250 0 V/cm over a separation length of 15 mm. Values of D- and L-aspartate in d ifferent tissues agreed well with those obtained by an HPLC procedure that required protein precipitation, centrifugation, and extraction. The speed a nd compatibility with automation of the microdialysis/CE method may make it a general approach for a variety of applications involving high-throughput analysis or sensorlike operation.