Preliminary study on the correlation between the trace Mn2+ and the calcite polymorph in gallstones containing calcium carbonate from the northeast China via electron spin resonance

Abstract

Gallstones containing calcium carbonate (GCCC) from the northeast China were analyzed using X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and electron spin resonance (ESR). The sextet signal arising from the allowed transitions of the trace Mn2+ ions in GCCC was found to be ESR-detectable and strong. The XRD technique revealed the crystal habit of calcite in GCCC. Of the three polymorphs of calcium carbonate, no calcite was present as a solitary crystallization form, accompanied by aragonite or vaterite or both. The sextet ESR signal and the (104) main XRD peak at 2θ = ∼29.4° were employed as two probes to explore the relationship between trace Mn2+ and calcite. The Mn content can be considered as an indicator of the amount of calcite in GCCC because of the existence of a correlation between Mn2+ and calcite. The correlation between Mn2+ and calcite, the relation between the levels of Mn2+ and the type of gallstones, the structural preference of Mn2+ to the calcite polymorph, and the influence of dietary habits on calcite in calcium carbonate gallstones are discussed.