GAS CHROMATOGRAPHIC-MASS SPECTROMETRIC ANALYSIS OF THE LOOP DIURETIC TORASEMIDE IN HUMAN URINE

A fast and reliable gas chromatographic-mass spectrometric (GC-MS) met hod for the identification and determination of the loop diuretic tora semide in human urine is described. The usefulness of different deriva tization procedures and reagents was studied. Flash methylation using trimethylanilinium hydroxide was the most convenient and appropriate p rocedure. The optimal urine isolation method comprised alkaline liquid -liquid extraction with ethyl acetate. After evaporation of the organi c layer to dryness, the solid residue was reconstituted in the derivat izing reagent and was directly injected into the GC-MS system. Samples were analysed in the multiple ion detection mode using electron impac t ionization. No interferences from other urinary compounds were found . Torasemide gave rise to a derivative that was identified by GC with Fourier transform infrared detection. There was a 70+/-5% recovery of torasemide. The coefficient of variation was 5% at a concentration of 0.05 mu g/ml. The method was used for the determination of torasemide in urine samples obtained from a healthy volunteer that had received a single, 10 mg dose of torasemide.