Zero-crossing first and second derivative Synchronous Fluorescence Spectroscopic determination of aspirin matabolites in urine

PATRICIA DAMIANI; GABRIELA IBAÑEZ; ALEJANDRO OLIVIERI

JOURNAL OF PHARMACEUTICAL AND BIOMEDICAL ANALYSIS

Elsevier

Lugar: Asterdam; Año: 1994 vol. 12 p. 1333 - 1335

0731-7085

Abstract The direct and simultaneous determination of main urine metabolites of aspirin, salicylic and salicyluric acids, without sample pre‑treatment procedures, is described. The method involves the application of first and second derivative synchronous fluorescence spectroscopy and the zero-crossing techniques. Salicyluric acid can be determinated by measurement of I2350 in the second derivative of the synchronous fluor­escence spectrum where the contri­bution of salicylic acid is negligible. Because no other zero‑crossing point appears to be available in order to measure the concentration of salicylic acid through both second and third derivative spectra, this determination can be done by the previously discussed use of I1325. Since both first and second derivative spectra are readily available from the spectrofluorimeter, the combined use of them should not present any complication. Furthermore, normal fluorescent urine components do not interfere at these wavelengths. The use of I2350 instead of I1350 in order to determine the content of salicyluric acid in urine should in principle give better results. Urine samples containing mixtures of salicylic and salicyluric acids were studied by the above procedure. The concentration of salicyluric acid was measured from the intensity of the second derivative of the synchronous fluorescence spectrum of the sample at lexc = 350 nm, after a calibration plot was prepared.