Enantioselective analysis of mirtazapine, demethylmirtazapine and 8-hydroxy mirtazapine in human urine after solid-phase microextraction

• Published in: Journal of separation science 2010-02, Vol.33 (2), p.268-276
• Main Authors: de Santana, Fernando José Malagueño, Jabor, Valquíria Aparecida Polisel, Cesarino, Evandro José, Lanchote, Vera Lúcia, Bonato, Pierina Sueli
• Format: Article
• Language: English
• Subjects: Antidepressive Agents, Tricyclic - administration & dosage; Antidepressive Agents, Tricyclic - analysis; Antidepressive Agents, Tricyclic - pharmacokinetics; Antidepressive Agents, Tricyclic - urine; Buffers; Chromatography, Liquid; Enantioselective analysis; Enzymes; Extraction; Fiber coatings; Human; Humans; Hydrogen-Ion Concentration; LC-MS; Methyl alcohol; Mianserin - administration & dosage; Mianserin - analogs & derivatives; Mianserin - isolation & purification; Mianserin - pharmacokinetics; Mianserin - urine; Mirtazapine; Osmolar Concentration; Phosphates; Reproducibility of Results; Solid Phase Microextraction - instrumentation; Solid Phase Microextraction - methods; Solid-phase microextraction; Stereoisomerism; Tandem Mass Spectrometry; Urine
• ISSN: 1615-9306; 1615-9314
• DOI: 10.1002/jssc.200900534

A selective and reproducible off‐line solid‐phase microextraction procedure was developed for the simultaneous enantioselective determination of mirtazapine (MRT), demethylmirtazapine and 8‐hydroxymirtazapine in human urine. CE was used for optimization of the extraction procedure whereas LC‐MS was used for method validation and application. The influence of important factors in the solid‐phase microextraction efficiency is discussed, such as the fiber coatings, extraction time, pH, ionic strength, temperature and desorption time. Before extraction, human urine samples were submitted to enzymatic hydrolysis at 37°C for 16 h. Then, the enzyme was precipitated with trichloroacetic acid and the pH was adjusted to 8 with 1 mol/L pH 11 phosphate buffer solution. In the extraction, the analytes were transferred from the aqueous solution to the polydimethylsiloxane‐divinylbenzene fiber coating and then desorbed in methanol. The mean recoveries were 5.4, 1.7 and 1.0% for MRT, demethylmirtazapine and 8‐hydroxymirtazapine enantiomers, respectively. The method was linear over the concentration range of 62–1250 ng/mL. The within‐day and between‐day assay precision and accuracy were lower than 15%. The method was successfully employed in a preliminary cumulative urinary excretion study after administration of racemic MRT to a healthy volunteer.