Determination of free-form of cocaine in rat brain by liquid chromatography-electrospray mass spectrometry with in vivo microdialysis

A rapid liquid chromatography-electrospray mass spectrometry (LC-ES-MS) met hod with in vivo microdialysis for the determination of free-form of cocain e (COC) in rat brain has been developed. A C-18 column and a gradient eluti on were employed for the separation. The [M+H](+) (m/z = 304) and a fragmen ted ion (m/z = 182) were detected using positive ion mode detection. Select ive ion monitoring was utilized for quantitative measurement. The Linearity of this assay was good ranging from 0.01 to 1.0 muM (r(2) = 0.999). The in ter- and intra-day precisions showed relative standard deviations ranging f rom 1.0% to 3.3% and 1.0% to 3.6%, respectively. In addition, the detection of one COC metabolite, benzoylecgonine (BE), by this assay was also invest igated. The linearity, precision, and detection limit associated with this method for BE were determined. The application of this newly developed meth od was demonstrated by examining the pharmacokinetics of COC in rat brain. (C) 2001 Elsevier Science B.V. All rights reserved.