Published:Journal of Chromatographic Science,
ISSN 0021-9665Volume
39, Number 11, November 2001, pp. 491-496
Simultaneous
Determination of Torasemide and Its Major Metabolite M5 in Human Urine by High-Performance
Liquid Chromatography– Electrochemical DetectionM.
Begoña Barroso, Rosa M. Alonso, and Rosa M. Jiménez Departamento de Química Analítica, Facultad
de Ciencias, Universidad del País Vasco/EHU, Apdo. 644, 48080 Bilbao,
Spain
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 µBondapack
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 µg/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.
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