Combination of salt–induced homogeneous liquid–liquid and solidified organic droplets dispersive liquid–liquid microextraction for extraction of some tricyclic antidepressants in urine samples prior to their determination by HPLC–UV

Nowadays, millions of people all over the world are affected with a common mental disorder named depression. This disorder causes the patients to experience serious problems such as depressed mood, feelings of guilt, disturbed sleep, and loss of interest or pleasure. The effective treatment of this disorder was proposed in the 1950s with the development of antidepressants which can elevate a patient s mood. The antidepressants commonly have been classified in two main groups: the monoamine oxidase inhibitors and tricyclic antidepressants (TCAs) [1]. TCAs are one of the oldest classes of antidepressants and imped the reuptake of serotonin and norepinephrine in the central nervous system [2]. Due to the narrow therapeutic range of TCAs, the development of sensitive and rapid analytical method for the determination of TCAs concentration in biological fluids in order to achieve the best therapeutic concentration with at least overdose and adverse problems is of great importance [3]. In this work, an efficient and green sample pretreatment method by combining salt induced–homogenous liquid–liquid extraction, dispersive solid phase extraction, and dispersive liquid–liquid microextraction based on the solidification of floating organic droplet has been developed for the extraction and preconcentration of some tricyclic antidepressant drugs (nortriptyline, amitriptyline, desipramine, clomipramine, and imipramine) in urine samples prior to their determination by high performance liquid chromatography–ultraviolet detection. In the suggested method, initially the analytes are extracted from urine samples into acetonitrile (ACN) separated by adding a salt. Then the obtained ACN phase is treated with a mixture of appropriate sorbents (50 mg PSA, 50 mg C18, and 25 mg GCB) to remove interferences. Afterward, the purified ACN is mixed with menthol as an extraction solvent and rapidly injected into alkaline HPLC–grade water as a preconcentration step. Next, after centrifuging the solution is placed in an ice bath and menthol is solidified and collected on the top of the solution. The solidified organic drop is then removed and dissolved in 10 µL ACN and injected into the separation system for quantitative analysis. Under the optimum experimental conditions, the enrichment factors and extraction recoveries of the selected drugs ranged from 345–420 and 69–84%, respectively. The limits of detection and quantification were obtained at the ranges of 0.22–0.31, and 0.71–1.1 µg L–1, respectively. The relative standard deviations of the proposed method for the selected analytes were ≤ 6% for intra– (n=6) and inter–day (n=4) precisions at a concentration of 10 µg L–1 of each analyte. Finally, the proposed method was used in the determination of the selected drugs in various urine samples.