Spectroscopic Studies of the Oxalate-Phosphate Interaction in Whewellite Calculi

Abstract

Since the beginning of our spectroscopic studies on urinary calculi (1) we have observed that a broad absorption near 1100 cm⁻¹ appears in the infrared spectra of whewellite stones (Fig. 1). At first, this band was tentatively attributed to the presence of sulphate ions, but a chemical analysis soon disproved this hypothesis. On calcination, the spectra showed that the band at 1100 cm⁻¹ shifted to 1035 cm⁻¹ (apatitic phosphate) and the oxalate transformed into the expected calcium carbonate and calcium oxide. This result led us to believe that the 1100 cm⁻¹ band might be related to the phosphorus contained in the organic matrix of the stones. However, due to the low quantity of phospholipids found in the samples by thin-layer chromatography, this hypothesis was also rejected. On the basis of these previous results, we considered that the band might be due to the presence of a kind of inorganic nonapatitic phosphate.