Identification of urinary stone components by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) has been used for the first time to study the composition of calcium oxalate (CaOxa) stones and uric acid stones. This technique allows for the identification and location of various inorganic and organic species at the same time. In CaOxa stones, there were less than 10% of phosphates. Sectional analyses of these stones indicated that the content of phosphorus in the stone center is higher than that in stone crust. In uric acid stones, CaOxa was rarely found. XPS is able to detect differences in chemical functionality. In uric acid stones, the binding energy (E-b) for nitrogen atoms were about 399.5 +/- 0.2 eV, which are largely characteristic of organic nitrogens N (- 3). In comparison, the E-b values of N (+5) in inorganic compounds are about 401 eV.