Rapid analysis of furosemide in human urine by capillary electrophoresis with laser-induced fluorescence and electrospray ionization-ion trap mass spectrometric detection.

Furosemide, a drug that promotes urine excretion, is used in the pharmacotherapy of various diseases and is considered as a doping agent in sports. Using alkaline electrolytes, analysis of furosemide by dodecyl sulfate based micellar electrokinetic capillary chromatography (MECC) and capillary zone electrophoresis (CZE) with laser-induced fluorescence detection (LIF, analyte excitation with the 325 nm line of a HeCd laser) is described. Data produced by injection of plain or diluted patient urines are confirmed with those obtained via analysis of urinary solid-phase extracts. CZE-LIF and MECC-LIF are thereby shown to permit unambiguous recognition of furosemide in urines collected after ingestion of therapeutic doses of this drug. This is in contrast to solute detection via UV absorbance for which the extraction of furosemide is required. MECC based electropherograms are somewhat more complex compared to those obtained by CZE-LIF, this suggesting that the latter approach is more suitable for rapid screening of urines with direct sample injection and LIF detection. Alternatively, capillary electrophoresis with negative electrospray ionization-ion-trap tandem mass spectrometry (CE-MS2) is shown to permit the direct confirmation of furosemide in human urine. This approach is based upon the monitoring of the m/z 329.3-->4m/z 285.2 precursor-product ion transition. CZE-LIF and CE-MS2 with injection of plain or diluted urine represent simple, rapid and attractive urinary screening and confirmation assays for furosemide in patient urines.