Figure 13 Electropherogram of dialysate sample taken after intraperitoneal tryptophan administration. Peak identification: kynurenine (KN) and tryptophan (Trp). (Reprinted with permission from Ref. 67.)

Microdialysis with off-line analysis has also been successfully employed for the investigation of the pharmacokinetics of an enantiomeric drug, isoproterenol [68, 69]. CE

has been shown to be an extremely powerful method for the separation of enantiomeric compounds. It is possible to place the chiral selector in the run buffer, precluding the need for very expensive modified LC columns. Due to the small volume requirements of CE, very little additive is required. CEEC with methyl-O-β-cyclodextrin as the modifier was used to monitor the pharmacokinetics of (−) and (+) isoproterenol by I.V. microdialysis sampling. Using a combination of peak stacking and electrochemical detection, limits of detection of 0.6 ng/mL were achieved. Isoproterenol has a very short half-life. A flow rate of 1 µL/min was used for the microdialysis sampling. It was possible to analyze the 1 µL samples and monitor the pharmacokinetics of the isoproterenol enantiomers with a temporal resolution of one minute (Figure 14).