New applications of fiberoptic IR spectroscopy in urologic practice

The objective of this work was to use infrared (IR) fiberoptic spectroscopy for the analysis of urinary salts. Urine samples were obtained (with no sample preparation) from two groups of patients: 24 stone forming patients, after shock wave lithotripsy, and 24 normal subjects of similar ages. IR absorption measurements were performed in real time, using Fiberoptic Evanescent Wave Spectroscopy system, based on IR transmitting silver halide fibers. The absorption data were compared with the IR spectra of aqueous solutions with known concentrations of known urinary salts. The results were then used for the study of the chemical composition of salts in urine samples and for a quantitative analysis of the concentration of these salts. We established the composition of the stones in 20 of the 24 stone forming patients, based on the characteristic absorption peaks for oxalates, carbonates, urates and phosphates observed in their urinary samples. We also determined the concentrations of these salts in the urine samples with average error of 20%.