Variable-angle scanning fluorescence spectrometry for the simultaneous determination of three diuretic drugs

The applicability of variable-angle synchronous scanning (VASS) fluorescence spectroscopy has been demonstrated for the resolution of mixtures of three diuretics (furosemide, triamterene, piretamide) with closely overlapping fluorescence profiles. This technique permits linear or non-linear paths to be scanned at preselected angles through the excitation-emission matrix by scanning both monochromators at different speeds, in order to obtain the best variable-angle scanning spectra (highest signal values and interference-free bands). Such an approach has permitted the simultaneous determination of the three compounds at the μg to ng ml−1 level, with a relative standard deviation ≤ 5% (n = 10). When applied to commercial pharmaceutical dosage forms, recoveries of the original drug between 98–101% have been obtained.