Determination of amitriptyline and nortriptyline in spiked plasma by capillary zone electrophoresis with β-cyclodextrin Original Research Article

A simple capillary zone electrophoresis (CZE) method was developed for the simultaneous analysis of amitriptyline (AMI) and its active metabolite (nortriptyline, NOR) in human plasma. This method was performed by Tris buffer (20 mM, pH 3.0) in the presence of β-cyclodextrin (0.2 mM). Several parameters affecting the separation of AMI and NOR such as the type and concentration of cyclodextrin, pH and concentration of Tris buffer were studied. Application of the method to the analysis of AMI and NOR spiked in plasma was conducted using clomipramine (CLO, 1 nmol) as an internal standard. After liquid–liquid extraction and concentration of AMI and NOR from plasma, the resulting residue was dissolved in aqueous acid prior to their analysis by capillary electrophoresis using UV detection (200 nm). In spiked plasma (1 ml) the quantitative ranges were 160–630 ng for AMI and 150–600 ng for NOR. The intra- and inter-day relative standard deviation (n=3) were all less than 10% for each substance. The detection limits for plasma samples were found to be about 60 ng/ml for AMI and 70 ng/ml for NOR (S/N=3, injection 20 s). All recoveries for AMI and NOR were greater than 80%.