title: Simultaneous determination of torasemide and its major metabolite M5 in human urine by high-performance liquid chromatography-electrochemical detection.
abstract: A high-performance liquid chromatographic method with electrochemical detection is described for the simultaneous determination of the loop diuretic 1-isopropil-3-[4-(3-methylphenylamino)-3-pyridinesulphonyl]urea (torasemide) and its major metabolite M5 in human urine. The assay is simple, fast, and easy. It requires a sample cleanup consisting of a solid-phase extraction under acidic conditions followed by chromatographic separation with a C18 microBondapack column. The use of a water-acetonitrile mobile phase (80:20, v/v, pH 3) ensures total separation from urine-interfering substances, and both compounds can be quantitated amperometrically at a glassy carbon electrode set to +1300 mV versus Ag-AgCl. The method demonstrates linearity for both the parent drug and the metabolite over a wide concentration range (up to 7 microg/mL) and reproducibility with relative standard deviation lower than 2% in intraday and 5% in interday assays. The mean extraction recoveries are 78% for M5 and 60% for torasemide, and the limits of quantitation are 1 and 8 ng/mL, respectively. The method developed is applied to the analysis of healthy volunteers' urine samples collected at different time intervals after the oral ingestion of a single dose of 10 mg torasemide, and the results obtained are in agreement with the pharmacokinetic profile of torasemide.
authors.affiliation: Departamento de Química Analítica, Facultad de Ciencias, Universidad del País Vasco/EHU, Bilbao, Spain.
authors.forename: M B
authors.initials: MB
authors.lastname: Barroso
authors.forename: R M
authors.initials: RM
authors.lastname: Alonso
authors.forename: R M
authors.initials: RM
authors.lastname: Jiménez
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004232:Diuretics / Q000652:urine*; D004563:Electrochemistry; D006801:Humans; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013449:Sulfonamides / Q000652:urine*; D000077786:Torsemide
chemical_list: D004232:Diuretics; D013449:Sulfonamides; D000077786:Torsemide