Analysis of bumetanide in human urine by high-performance liquid chromatography with fluorescence detection and gas chromatography/mass spectrometry.

Bumetanide is a potent diuretic. Its concentration in urine after therapeutic doses is in the low ng/mL range. A procedure using reversed-phase HPLC with fluorescence detection is described. Using this procedure, the authors have been able to measure bumetanide in a urine sample at 10 ng/mL with a signal-to-noise ratio of 7. Therefore, the detection limit is lower than this concentration. Confirmation is by a GC/MS procedure after methylating the diuretic. Derivatization is by extractive alkylation with tetrabutylammonium hydrogen sulfate as the phase transfer reagent and iodomethane as the methylating agent.