Solid phase extraction procedure coupled with the chiral LC-ESI-MS/MS method for the enantioseparation and determination of butoconazole enantiomers in rat plasma and tissues: application to the enantioselective study on pharmacokinetics and tissue distribution

In the present study, a highly rapid, sensitive and enantioselective method was developed and fully validated for the separation and determination of butoconazole enantiomers in rat plasma and tissues by liquid chromatography-electrospray ionization coupled with tandem mass spectrometry (LC-ESI-MS/MS). The analytes and internal standard (tioconazole) were both extracted from plasma and tissue samples by the solid phase extraction (SPE) procedure with C-18 cartridges. Satisfactory enantioseparation was achieved on a Chiralpak IC column by using acetonitrile/10 mM aqueous ammonium acetate (90 : 10, v/v) as a mobile phase. Butoconazole enantiomers and IS were detected in the multiple reaction monitoring (MRM) mode with a positive electrospray ionization source. A comprehensive validation of this method was conducted over the concentration range of 0.5-250 ng mL(-1), and good linearity was obtained for each enantiomer with correlation coefficient (R-2) greater than 0.991. The mean extraction recoveries were higher than 90.4%, and the relative error was well within the admissible range of -8.0 to 9.1% and the relative standard deviation was less than 11.5%. All the validation data demonstrated that the desirable specificity, carry-over, linearity, sensitivity, accuracy, precision, extraction recovery, matrix effect and stability were attained from the proposed approach. After validation, the established method was successfully applied to the study on stereoselective pharmacokinetics and tissue distribution in female Sprague-Dawley rats after transdermal administration of 10 mg kg(-1) 2% rac-butoconazole nitrate cream. It should be noted that this is the first report regarding the stereospecific study of butoconazole enantiomers in vivo.