Study of calcium oxalate monohydrate of kidney stones by X-ray diffraction

Abstract

X-ray powder diffraction was used to study the phase composition of human renal calculi. The stones were collected from 56 donors in Vitória, Espírito Santo state, southeastern Brazil. An XRD phase quantification revealed that 61% of the studied renal stones were composed exclusively of calcium oxalate ͓34% formed only by calcium oxalate monohydrate ͑COM͒ and 27% presents both monohydrate and dihydratate calcium oxalate͔. The 39% multi-composed calculi have various other phases such as uric acid and calcium phosphate. Rietveld refinement of XRD data of one apparent monophasic ͑COM͒ renal calculus revealed the presence of a small amount of hydroxyapatite. The presence of this second phase and the morphology of the stone ͑ellipsoidal͒ indicated that this calculus can be classified as non-papillary type and its nucleation process developed in closed kidney cavities. In order to show some advantages of the X-ray powder diffraction technique, a study of the phase transformation of monohydrate calcium oxalate into calcium carbonate ͑CaCO 3 ͒ was carried out by annealing of a monophasic COM calculi at 200, 300, and 400°C for 48 h in a N 2 gas atmosphere. The results of the XRD for the heat treated samples is in good agreement with the thermogravimetric analysis found in the literature and shows that X-ray powder diffraction can be used as a suitable technique to study the composition and phase diagram of renal calculi.

Anhydrous Calcium Oxalate Polymorphism: A Combined Computational and Synchrotron X-ray Diffraction Study

“…Because of this, and together with the fact that calcium oxalate is frequently found as a biomineral in plants, research into the phases of calcium oxalate, including its hydrates, is attracting significant attention. [4][5][6][7][8][9][10][11][12][13][14] 4,6,[15][16][17][18][19][20] As in the case of calcium carbonate, an amorphous phase has also been detected for calcium oxalate, with a degree of hydration close to 1 molecule of water per formula unit. 21,22 On the other hand, understanding the structure and polymorphism of anhydrous calcium oxalate (COA) directly from experiment is a challenge due to the fact that it is highly hygroscopic and therefore little work has been done so far on these phases.…”

Novel iron doped calcium oxalates as promising heterogeneous catalysts for one-pot multi-component synthesis of pyranopyrazoles

“…The powder diffraction database was used for the phase identication, which revealed that the XRD patterns of all samples well matched with the COM phase (PDF 20-0231). 47 The identied peaks projected at d ¼ 5.83, 3.60, 2.94, 2.47, 2.33, 2.25, and 2.06Å corresponding to COM crystal, were assigned to (À101), (020), (À202), (112), (130), (202), (321) lattice planes, respectively. The doping of iron into the COM lattice did not create any new phase, conrming that iron occupied the interstitial position of COM crystals (Fig.…”

Biomineralization in human pancreas: A combined infrared-spectroscopy, scanning electron microscopy, x-ray Rietveld analysis, and thermogravimetric study

“…With the development of x-ray powder profile-fitting structure refinement using the Rietveld method, 26-28 the quantitative estimates of mineral phases in urinary or PSs can now be accomplished with an increased accuracy. 12,13,29 This method also provides the microstructural features intrinsic to crystalline environment, e.g., grain size, microstrain, and preferred orientation. These factors are important when attempting to elucidate the mechanism for in vivo crystal growth.…”