PHOSPHATES IN URINARY CALCULI
V.N. Stolpovskaya, N.A. Pal'chik, T.N. Grigoreva., T.A. Korneva
United Institute of Geology, Geophysics and Mineralogy Siberian Branch of Russian Academy Science. Pr. Koptyuga, 3. Novosibirsk. Russia
Keywords: urinary calculi, phosphate, analysis, IR spectroscopy, X-ray powder diffraction.
Mineral constituents of organic-mineral pathogenic formations, in particular, urinary calculi provide «visiting card» of diseases accompanying their occurrence. Yet not only a composition but structure properties of constituent minerals as well as their distribution over a volume of mixed stones have been important parameters reflecting features of an «environment» and its changing in the course of the development and growth of stones [1]. We have considered phosphate-containing urinary calculi and selected among them ones mainly composed of apatite and struvite for detail study. The third phosphate occasionally presenting in a large measure in these calculi is whitlokite which is more frequent in association with apatite. Apatite is of greatest interest owing to the possibility of a comparison between its structure features and well studied properties of inorganic and biological (physiogenic) apatites [2].
The composition and structural peculiarities of minerals of urinary calculi have been analyzed with the use of IR spectroscopy, X-ray powder diffraction and thermal analysis. Reflections in the X-ray diffraction patterns from stones with nearly pure apatite are low-intense, broadened and weakest ones are absent at all indicating the very poor crystallinity of the substance. According to IR-spectroscopy data that is high-carbonated apatite with a large amount of «bound water». After ignition of samples at 4000C directly in KBr disks for two hours water is completely removed as well as organic matter (the amount of latter is 6-7% according to thermogravimetry data). In this case the structure of apatite itself is slightly improved and intensities of absorption bands of structural CO32- -ions remain unchanged. OH groups are removed at higher temperatures (maximum of endothermic peak is at 6800C). Carbonate content in apatite is estimated from IR spectra by the ratio of the extinction of the 1415 cm-1 carbonate mode to that of the 575 cm-1 PO43- band [3] using the calibration curve plotted for carefully analyzed nature dahlites for CO2. For all analyzed urinary stones the carbonate content lies in the range 3.7-4%. Absorption bands of CO32- -ions are less intensive for samples in which apatite exists together with witlocite, perhaps according to the apatite portion in a sample. We do not find samples with well crystallized apatite whereas such samples are found among struvites and whitlokites. It is conceivable that in urinary stones at least considered by us (in all 6 samples) apatite is high-carbonated and poorly crystallized.
Pathogenic apatite in urinary stones for a
number of parameters is close to sedimentary and biological
apatites, but they are differ from each other in some properties.
One of them is very low crystallinity degree related to the
crystallization condition.
This work was supported by RFFI, grant N 97-05-65305.