Highly selective determination of some anti‐depressant drugs in complicated matrices by dual emulsification liquid‐phase microextraction based on filtration followed by high‐performance liquid chromatography

An efficient microextraction method is applied for the determination of some anti‐depressant drugs in complex matrices. The method consists of two steps. In the first step, an organic extraction solvent is dispersed into an aqueous sample solution (20 mL, pH 12), and the resulting mixture is subsequently passed through a hydrophilic polytetrafluoroethylene syringe filter that is permeable to aqueous solutions, and thus the organic phase is retained by the membrane. In the second step, the filter is detached from the syringe and attached to another syringe containing an aqueous solution (pH 2, 150 μL). By the in‐syringe dispersion of the organic phase into the aqueous phase, the target analytes are ionized and selectively back‐extracted into the aqueous phase. In addition to the preconcentration of the analytes in the aqueous phase, which can cause the elimination of the problem of injection of the organic solvent into the final instrument analyzer as well, the method provides a high sample clean‐up since acidic compounds, large molecules, and neutral components are not extracted into the acceptor phase. Under the optimized experimental conditions, the method provides a good linearity (in the range of 5–2000 ng mL −1 ) and a low limit of detection (1.5–3.0 ng mL −1 ).