Identification of human calculi with time-of-flight secondary ion mass spectrometry.

Time-of-flight secondary ion mass spectrometry was used to study four human calculi and to compare the results with those from twelve commercially available urinary calculi minerals including three organic compounds (L-cystine, uric acid and sodium urate). Phase identification of calcium phosphate compounds was carried out by considering the relative ion abundances of [Ca(2)O](+) and [CaPO(2)](+). Deprotonated [M-H](-) and protonated [M+H](+) uric acid were detected and used for component recognition in pure uric acid and in the mixed samples of struvite, calcium oxalate and uric acid. Iodine related to the medical history of a patient was also detected.