Enantiomeric separation of mirtazapine and its metabolite in rat plasma by reverse polar ionic liquid chromatography using fluorescence and polarimetric detectors connected in series

A simple and rapid reverse polar ionic LC method was developed and validated for simultaneous separation and determination of mirtazapine, an antidepressant drug, and its main metabolite N-desmethyl mirtazapine using fluorescence and polarimetric detectors connected in series. The chromatographic separation was achieved on Chirobiotic V column packed with vancomycin as a stationary phase in an isocratic mode of elution of methanol:glacial acetic acid:anhydrous triethyl amine (100:0.2:0.1, v/v/v) as a mobile phase. The compounds were detected by their excitation at 290 nm and emission at 370 nm using fluorescence detector while the optical rotation (+/−) of the enantiomers was identified by polarimetric detector. The analytes were extracted from rat plasma by precipitation of proteins and the average yield was 88–111% for mirtazapine and 85–123% for N-desmethyl mirtazapine. The method was linear over the concentration range of 20–5000 ng/mL. The method was successfully applied on rat plasma spiked with the enantiomers of mirtazapine and N-desmethyl mirtazapine.