Development of microextraction by packed sorbent for toxicological analysis of tricyclic antidepressant drugs in human oral fluid

The aim of this study was to apply microextraction by packed sorbent (MEPS) to the isolation of six tricyclic antidepressants (TCADs): nordoxepin, doxepin, desipramine, nortriptyline, imipramine, and amitriptyline from human oral fluid. Samples were collected from healthy volunteers via free spillage from the oral cavity to disposable test tubes. A method of oral fluid sample pretreatment was developed and optimized in terms of suitability for MEPS extraction and removing of interfering agents (protein, food debris, or air bubbles). Moreover, it was short and simple to perform with limited sample consumption (150 μL). Extracts were analysed by UHPLC–MS. The MEPS/UHPLC–MS method was validated at three concentration levels (2.00, 4.00 and 8.00 ng/mL) of all analytes in the range 1.25–10.0 ng/mL. The following parameters were determined: limit of detection, limit of quantification, precision, and accuracy. For all tested concentration levels, the intra- and inter-day repeatability did not exceeded 8.1% and 12.2%, respectively. Gained LOQ value, 0.50 ng/mL, made the MEPS/UHPLC–MS method to be a useful tool in clinical and forensic laboratories, which was demonstrated on the basis of analysis of real samples.