Direct analysis of amiloride and triamterene mixtures by fluorescence spectrometry using partial-least squares calibration

The simultaneous determination of amiloride and triamterene in urine sample s using fluorimetry in combination with partial-least squares (PLS) multiva riate calibration is proposed. Triamterene and amiloride exhibit overlapped spectra and urine produces background fluorescence that precludes the dire ct determination of these diuretics by conventional fluorimetry. Although, the qualitative composition of the fluorescent metabolites in urine from he althy people is virtually invariable, their quantitative composition exhibi ts some differences. Thus, the shape of the spectrum and the position of th e fluorescence maxima change as the urine is diluted. The determination was performed in a 1:1 (v/v) ethanol/water medium at an a pparent pH of 6.3 provided by 0.01 M sodium citrate/citric acid buffer. An excitation wavelength of 365 nm was used for both amiloride and triamterene . The corresponding emission maxima were located at 413 and 437 nm for amil oride and triamterene, respectively. A calibration set consisting of samples standards was used in combination w ith a factor design; two levels per factor and a central star design (i.e. a central composite design) were used. In order to ensure accurate results, the calibration matrix was implement an urine sample containing no triamte rene or amiloride (i.e. urine blank). The components of the calibration mat rix were triamterene, amiloride and urine. The concentration of amiloride w as varied from 64 to 320 ng/ml and that of triamterene from 20 to 100 ng/ml . Urine dilution was varied from 1:35 to 1:65. Urine was used as the third component of the calibration matrix in order to include the information inh erent in changes in the fluorescence spectrum for urine upon dilution. (C) 2001 Elsevier Science B.V. All rights reserved.