| Abstrakt: |
Calcium carbonate crystallization was experimentally modeled in a model human bile solution. CaCO3 samples were prepared in the presence of variable concentrations of histidine (His), arginine (Arg), methionine (Met), or tryptophan (Trp). The phase and structure-group compositions of the prepared samples were determined by X-ray powder diffraction and FT-IR spectroscopy. CaCO3 percentages, particle sizes, and volume proportions of various size fractions in the prepared powders were determined. The samples prepared in the presence of Arg have the highest yield as impurity-free CaCO3; those prepared in the presence of Met have the lowest yield. The increasing amino acid (AA) concentration gives rise to an increase in the calcium carbonate weight fraction in the syntheses with His or Arg and to a decrease in the syntheses with Met or Trp. The major component of the phase composition in all of the prepared powders is represented by vaterite, a metastable CaCO3 polymorph. The proportion of the aragonite fraction in the solid increases as the Arg or Met concentration in bile increases. Calcium carbonate microparticles with radii less than 10 µm are represented by three fractions. As the His or Trp concentration in the model bile solution increases, the proportion of the small-size fraction increases while the proportion of the coarse-size fraction decreases, with the particle radii increasing in all fractions. [ABSTRACT FROM AUTHOR] |
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