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Abstract
Time-of-flight secondary ion mass spectrometry was used to study the real urinary stones and the results were compared with those from commercially available urinary calculi organic compounds and minerals. Organic urinary stone components like uric acid and cystine were clearly identified by their respective protonated molecules [M+H]+ and deprotonated molecules [M-H]-. With TOF-SIMS analysis we clearly distinguished between uric acid and its sodium/potassium urates. The mass spectra of cystine stones were compared with those measured for the standard compounds, cystine and its monomer cysteine. Similar spectra were obtained for the stones and cystine. The most important identification was based on the existence of the protonated molecules [M+H]+ and deprotonated molecules [M-H]-.
The calcium oxalate (COX) stones were recognized by the presence Ca+2, Ca+, CaO+, CaOH+, Ca2+, Ca2O+, Ca2O2+, and Ca2O2H+ ions. The calcium phosphate stones were recognized with the presence of aforementioned ion peaks for calcium oxalate along with additional phosphate containing ions. Moreover, the phase identification of calcium phosphates was achieved in the positive SIMS mode on basis of the PO+/POH+ and CaPO2+/Ca2O+ peak ratios. We also quantified the calcium phosphate (up to < 3%) in the human calculi containing calcium oxalate as major or minor component, which is of a great interest for medical community, and the reliable phase identification of calcium phosphates also has potential application in bio-implant technology.
Struvite (NH4MgPO4.6H2O) stones, also known as infection stones due to their association with ureasplitting bacteria were confidently identified by the presence of its major characteristic peaks of NH4+, Mg+, PO2-, PO3-. We also observed uric acid, sodium/potassium urates, apatite [Ca10(PO4)6(OH,CO3)] and tri-calcium phosphate [Ca3(PO4)2] in struvite stones.
In our studies we also identified unusual components namely calcium formate Ca(HCO2)2, metabolite of vitamin B6 (4-deoxypyridoxine 5-phosphate) and iodine in three human stones.
Last but not least, the VG Ionex TOF-SIMS instrument used for this new application was upgraded which enables us to perform extensive experimental work for this study and for plentiful collaborated work published and being prepared for publications.
