Ultrasensitive Analysis of Mirtazapine and its Metabolites Enantiomers in Body Fluids Using Ultrasound-Enhanced and Surfactant-Assisted Dispersive Liquid–Liquid Microextraction Followed by Polymer-Mediated Stacking in Capillary Electrophoresis

•We obtained satisfactory recoveries, good sensitivity, and non-interfering eletrophoretic analysis.•Our developed system was used to quantify mirtazapine-related drugs in human fluids.•Ultrasensitive analysis of mirtazapine-related drugs was achieved by the proposed system.•The sensitivity was improved to 2700–3900 times by USA-DLLME and PDDAC-mediated CE stacking.•This system has the merits of simplicity, rapidity, separation efficiency, and sensitivity.