Fourier transform infrared spectroscopy (FT-IR) and Fourier transform Raman spectroscopy (FT-RS) were used in order to characterize the encrusted deposits formed on a metallic thermosensitive prostatic stent. A 4 mm urinary stone entrapped within the lumen was also analyzed. Six different substances, a very rare occurrence, were detected, yielding complex spectra. Struvite (STR), hydroxyapatite (HAP), calcium oxalate monohydrate (COM), potassium urate (PU), and ammonium urate (AU) were the main components of concretion formed on the metal surface. STR and PU were detected on the 0.2 mm external surface of the stone, while the 3.8 mm core was found to be uric acid (UA). The broad and overlapping FT-IR bands of STR and COM made their identification difficult, while the detection of HAP was hindered by the presence of numerous urates bands, which, on the other hand, were used for the discrimination among UA, AU, and PU. Raman spectroscopy proved to be more sensitive to urate presence than did FT-IR, while the identification of STR, COM, and HAP was easier for FT-RS but more difficult with respect to AU and UA since all their bands, but three, coincide. A combination of the two techniques was necessary for the qualitative analysis of the encrustation and the stone.
C. G. Kontoyannis, N. Bouropoulos, H. H. Dauaher, C. Bouropoulos, and N. V. Vagenas, "Analysis of Prostatic Stent Encrustation and of Entrapped Urinary Stone Using FT-IR and FT-Raman Spectroscopy," Appl. Spectrosc. 54, 225-229 (2000)