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In the present work we report a non-aqueous electrophoresis method (NACE) for the separation and determination of eight tricyclic antidepressants (TCAs) in human serum. Separation is carried out in 1 M acetic acid, 50 mM ammonium acetate and 10 mM SDS in ACN. Standards and samples were prepared in 0.8 M acetic acid in ACN and introduced by electrokinetic injection. The interactions between TCAs and acetate ions were studied and deduced from comparison of both the actual experimental and theoretical mobility. The establishment of calibration curves in the presence or absence of serum matrix, between 20 and 200 ng/mL, together with the determination of most important analytical parameters and a study of robustness were performed. Validation of the CE method was carried out with serum samples spiked with the analytes. The NACE determination method offers better resolution and higher sensitivity than the determination of TCAs in aqueous media.

Stacking methods are very important in overcoming the poor detection limits in capillary electrophoresis (CE). In this paper, the separation and determination of several tricyclic antidepressants by a stacking method is described. The inclusion of acetonitrile (ACN) in the sample causes stacking (transient pseudoisotachophoresis) especially in presence of sodium chloride. An experimental design (central composite design) together with the response surface methodology has been used to find the optimum composition of the separation buffer and the optimal stacking conditions in few experiments. The response functions used are the product of the total resolution by the number of peaks, for the optimization of the separation buffer, and the product of the total resolution by the mean of the peak heights, for the optimization of the stacking conditions. About 28% of the capillary volume is loaded with sample. The calibration curves are linear over the working range (50-300 ng/mL). With a bubble capillary, the limits of detection (LODs) are in the order of 5 ng/mL. For the analysis of serum samples, enrichment with sodium chloride and the protein precipitation with ACN are enough to avoid interferences and to get stacking. Recoveries between 91.6 and 104% and RSD between 0.6 and 12% are obtained in the analysis of samples of lyophilized human serum and non-lyophilized human serum, spiked with the drugs.