Background: Mixed anxiety depressive disorder is commonly treated with a mixture of an
antidepressant and a benzodiazepine drug. Quality control to ensure that these products comply with the
specifications is required. To improve the quality control of pharmaceutical products throughout the
world, accessible analytical methods are needed.
Objective: The aim was to develop fast, simple, cheap, accurate and easily accessible analytical methods
for the simultaneous determination of selected antidepressant mixtures by high performance liquid chromatography.
The first mixture contained amitriptyline, chlordiazepoxide and nortriptyline as an impurity of
amitriptyline, while the second one was imipramine and alprazolam in a challenging component ratio.
Method: Both chromatographic methods used a 5 cm length Phenomenex C18 column. The mobile phase
was acetonitrile - 0.05 M phosphate buffer pH 3 (25:75, v/v) for the first mixture, and acetonitrile - 0.05
M phosphate buffer pH 2.8 (30:70, v/v) for the second mixture. The UV- detector was set at 240 nm.
Results: The methods show good linearity in the range 0.1 - 100 µg mL-1 for both amitriptyline and chlordiazepoxide
and 0.1 - 20 µg mL-1 for nortriptyline in the first mixture. The second mixture shows linearity
over 1 - 400 µg mL-1 for imipramine while alprazolam was linear from 0.1 to 10 µg mL-1. The accuracy
and precision of the methods have been determined by analyzing laboratory prepared pharmaceutical
mixtures. Both methods proved to be specific, robust and accurate according to the International
Conference on Harmonization guidelines and can be applied in quality control of these drugs.
Conclusion: Short reversed phase columns provided separation in a few minutes for the mixture of
amitriptyline and chlordiazepoxide (containing nortriptyline) as well as imipramine and alprazolam.