Development of a new hyphenated sample preparation method in combination with GC–MS for extraction and determination of some tricyclic antidepressants in biological fluids

Tricyclic antidepressants (TCAs) are one of the classes of psychopharmaceuticals which still are widely used for the treatment of various forms of depression and psychological disorders [1]. TCAs inhibit the reuptake of neurotransmitters by impeding serotonin and norepinephrine transporters [2]. Generally, therapeutic drug monitoring is becoming highly important as it can help for effective control of pharmacotherapy and drug poisoning in clinical pharmacology and forensic sciences. This point is more important in the case of TCAs because of their narrow therapeutic range. The concentrations of these drugs in human biological fluids are at very low levels and mainly determined by chromatographic methods [3, 4]. In most cases, an additional step termed as sample preparation which includes extraction, preconcentration, and cleanup is mostly required for pharmaceutical analysis due to the inherent complexity of the biological fluids. In this study, dispersive solid phase extraction coupled with deep eutectic solvent–based air–assisted liquid–liquid microextraction has been developed and applied to the extraction and preconcentration of some tricyclic antidepressant drugs in human urine and plasma samples prior to their determination by gas chromatography–mass spectrometry. In this method, firstly, a sorbent is added into an alkaline aqueous sample and dispersed by vortexing. By this action the analytes are adsorbed onto the sorbent. Then the sorbent particles are isolated from the aqueous solution by centrifugation. Afterward, a synthetic deep eutectic solvent is used to desorb the analytes from the sorbent. Subsequently, the supernatant solution is removed and added into an alkaline deionized water placed into a test tube with conical bottom. The resulting mixture is rapidly sucked into a glass syringe and then is injected into the tube. This procedure is repeated for several times, and a cloudy solution consisting fine droplets of deep eutectic solvent dispersed into the aqueous phase is formed. After centrifuging the obtained cloudy solution, the tiny droplets of the extractant containing the extracted analytes are settled at the bottom of the tube. Finally, an aliquot of the extractant is taken and injected into the separation system for analysis. Several significant factors affecting the performance of the proposed method were evaluated and optimized. Under the optimum extraction conditions, the method showed low limits of detection in the ranges of 8–15 and 32–60 ng L−1 in urine and plasma, respectively. Enrichment factors were obtained between 163 to 193 in urine and 65 to 77 in plasma for the analytes. Extraction recoveries were in the range of 65–77%. The relative standard deviations of the proposed method were ≤ 6% for intra– (n=6) and inter–day (n=4) precisions. Finally, the applicability of the introduced method was investigated by analysis of the selected drugs in different patient s biological fluids.