Capillary electrophoretic separation of tricyclic antidepressants using a polymer-coated capillary and β-cyclodextrin as an electrolyte additive

A new method for the CE separation of nine tricyclic antidepressants (TCAs), viz. amitriptyline, clomipramine, desipramine, doxepin, fluphenazine, imipramine, nortriptyline, promazine, and thioridazine, is described. The capillary was statically coated with a layer of poly(N,N-dimethylacrylamide) (PDMA) to suppress the EOF, and beta-CD was used as an additive in the BGE solution. The optimal resolution of nine TCAs was obtained by using a 1% v/v PDMA-coated capillary and a BGE solution of 50 mM sodium phosphate buffer (pH 3.0) containing 0.5 mM beta-CD. Efficiencies were typically > 10(5) plates/m. Complete separation of nine TCAs could be achieved in about 28 min; the two diastereomers of doxepin and the two enantiomers of thioridazine could also be separated. The RSD values of migration time and peak area of the TCAs were in the ranges 0.5-0.8 and 3.3-4.9% (n = 10), respectively. In combination with a Suitable sample clean-up technique, such as hollow fiber-based liquid phase microextraction (HF-LPME), the polymer-coated capillary can be employed for the CE-UV analysis of TCAs in human plasma.