Quantitative analysis of urinary stone composition with micro-Raman spectroscopy

Urolithiasis is a common, disturbing disease with high recurrent rate (60% in five years). Accurate identification of urinary stone composition is important for treatment and prevention purpose. Our previous studies have demonstrated that micro-Raman spectroscopy (MRS)-based approach successfully detects the composition of tiny stone powders after minimal invasive urological surgery. But quantitative analysis of urinary stones was not established yet. In this study, human urinary stone mixed with two compositions of COM, HAP, COD, and uric acid, were analyzed quantitatively by using a 632.98 nm Raman spectrometric system. This quantitative analysis was based on the construction of calibration curves of known mixtures of synthetically prepared pure COM, HAP, COD and uric acid. First, the various concentration (mole fraction) ratio of binary mixtures including COM and HAP, COM and COD, or COM and uric acid, were produced. Second, the intensities of the characteristic bands at 1462cm ^-1(I_RCOM), 1477cm^-1(I_RCOD), 961cm^-1(IRHAP) and 1402cm^-1(I_{Ruric acid}), for COD, COM, HAP and uric acid were used respectively for intensity calculation. Various binary mixtures of known concentration ratio were recorded as the basis for the quantitative analysis. The ratios of the relative intensities of the Raman bands corresponding to binary mixtures of known composition on the inverse of the COM concentration yielded a linear dependence. Third, urinary stone fragments collected from patients after management were analyzed with the use of the calibration curve and the quantitative analysis of unknown samples was made by the interpolation analysis. We successfully developed a MRS-based quantitative analytical method for measuring two composition.