Comparison of Directly Suspended Drop Microextraction with Dispersive Liquid-liquid Microextraction Method for Extraction of an Antidepressant Drug in Biological Samples Prior to UV-Vis Spectrophotometer

Depression is one of the serious global economic problems because the patients often lose the ability of working. In addition, depression may ultimately result in suicide [1]. The depression treatment includes various forms of psychotherapy as well as pharmacotherapy with antidepressant drugs. Tricyclic antidepressants (TCAs) are a group of important drugs that are widely used for the treatment of this psychiatric disorder. Sometimes, they are encountered for emergency toxicology screening, forensic medical examinations and drug-abuse testing [2-4]. Due to the complexity of biological samples, the sample pretreatment process has become the bottleneck in method development and sample analysis in many cases [5]. The main aim of this research is using two different preconcentration and sample preparation methods: directly suspended drop microextraction and air-dispersed liquid-liquid microextraction methods which are coupled with UV-Vis spectrophotometer for the analysis of doxepin in biological samples. Several important parameters which influence the extraction efficiencies of these two microextraction methods, such as kind of the extracting solvent, volume of the aqueous sample solution (donor phase), volume of the organic extraction solvent (acceptor phase), pH of the donor phase, salt effect, extraction time, stirring rate and number of the air injection were investigated. Under the optimal conditions the enrichment factors were above than 30. The linearity of the methods has been investigated between the ranges of 0.005-1.5 and 0.003-1 µg mL-1. The precisions of two methods which are based on the average relative standard deviations are lower than 6, for three different concentrations of the analyte. Finally, the proposed methods were applied for the determination of doxepin in biological samples including urine and human plasma under the optimal conditions and the reasonable relative recoveries were obtained which are above 88%.