Method for simultaneous determination of eight cyclic antidepressants by cyclodextrin-modified capillary zone electrophoresis: applications in pharmaceuticals

Our research team established a selective capillary zone electrophoresis method for the simultaneous determination of amitriptyline HCl, clomipramine HCl, trimipramine maleate (racemate, including R/S, 1:1), nortriptyline HCl, protriptyline HCl, maprotiline HCl, doxepin HCl (including 16.75% of Z-form and 83.25% of E-form), and desipramine HCl. The background buffer was Tris (500 mM, pH 3.50) containing (beta)-cyclodextrin (1.5 mM), hydroxypropyl-(beta)-cyclodextrin (1.5 mM) and 13% (v/v) of acetonitrile in an untreated fused-silica capillary. Analysis was run at a voltage of 20 kV and a detection wavelength of 200 nm. In the method validation, the calibration curves are linear over a range of 125.0–500.0 (mu)M (r > 0.9974). The R.S.D. and R.E. were all less than 3% for the intra- and inter-day assays. All recoveries were greater than 95%. The limit of detection was Z-doxepine, 4 (mu)M; protriptyline, trimipramine-1 or trimipramine-2, 10 (mu)M; E-doxepine, nortriptyline, maprotiline, amitriptyline, clomipramine, despramine, 5 (mu)M (S/N = 5, hydrodynamic injection 3 s). Our method was applied to commercial tablets (maprotiline, amitriptyline, clomipramine) and capsules (doxepine). All analytical values were within the labeled amount of 90–110% required by the USP XXV.