Hollow fiber based liquid–liquid–liquid microextraction combined with sweeping micellar electrokinetic chromatography for the sensitive determination of second-generation antidepressants in human fluids

Abstract

An effective dual preconcentration method involving off-line hollow fiber liquid–liquid–liquid microextraction (HF-LLLME) and on-line sweeping micellar electrokinetic chromatography (sweeping-MEKC) was proposed for the determination of five second-generation antidepressants, including fluoxetine, sertraline, paroxetine, fluvoxamine and citalopram. In HF-LLLME, the analytes were extracted from the sample solution into phenetole impregnated in the pores of the hollow fiber and then back-extracted into 10 μL 0.1 mol L⁻¹ HAc inside the hollow fiber. Then, the acceptor phase was spiked with 2.8 μL isopropanol (IPA) and introduced into CE for sweeping. In the sweeping-MEKC process, five target analytes were separated in less than 15 min with a background electrolyte consisting of 76% (v/v) 50 mmol L⁻¹ citric acid (pH 2.2) containing 100 mmol L⁻¹ sodium dodecyl sulfate (SDS) and 24% (v/v) IPA. The hydrodynamic injection was performed at 50 mbar for 140 s. Under optimized conditions, the limits of detection were in the range of 0.40–1.55 μg L⁻¹ with enrichment factors of 1897- to 5952-fold for target analytes, with a dynamic linear range of 0.6/5.0–200 μg L⁻¹. The developed method demonstrated excellent clean-up ability and high enrichment factors and was successfully applied to the analysis of target analytes in human urine and plasma samples.