Comparison of hydrodynamically closed two-dimensional capillary electrophoresis coupled with ultraviolet detection and hydrodynamically open capillary electrophoresis hyphenated with mass spectrometry in the bioanalysis of varenicline.

Two capillary electrophoresis methods for monitoring renally excreted varenicline, a highly effective drug prescribed for smoking cessation, in human urine were developed and compared. A method combining capillary electrophoresis with mass spectrometry was proposed for the fast analysis of varenicline (analysis time up to 7 min). Here, mass spectrometry was a prerequisite for achieving high sensitivity and selectivity of the analysis suitable for the quantification of a 15 ng/mL level of varenicline in un-pretreated urine matrices. An alternative approach, two-dimensional (column-coupled) capillary electrophoresis with enhanced sample load capacity and ultraviolet detection, was proposed as a low-cost alternative to capillary electrophoresis with mass spectrometry. The isotachophoresis on-line sample treatment included simple elimination of the major matrix constituents and stacking of the sample in a large volume so that threefold lower quantitation limits could be easily achieved in comparison to the capillary electrophoresis with mass spectrometry. On the other hand, longer analysis time (ca. 4.5-fold) and more complex electrolyte system in the coupled zone electrophoresis step (including two additives enhancing separation selectivity, i.e. isopropanol and cyclodextrin) were prerequisites for the complete separation of varenicline from the sample matrix. Anyway, both the developed methods were validated according to the Food and Drug Administration guidelines showing favorable performance parameters, suitable for their routine biomedical use.