Quantitative analysis of synthetic calcium carbonate polymorphs using FT-IR spectroscopy.

Fourier Transform Infrared Spectroscopy (FT-IR) was used successfully for the simultaneous quantitative analysis of calcium carbonate phases (calcite, aragonite, vaterite) in ternary mixtures. From the FT-IR spectra of pure calcite, aragonite and vaterite powders with KBr, the absorptivities, alpha, of the absorption bands at 713 cm(-1) for calcite, 745 cm(-1) for vaterite, 713 and 700 cm(-1) for aragonite, were determined. In order to overcome the absorption band overlapping a set of equations based on Beer's law was developed. The detection limits were also established and found to be 1.1 x 10(-4) mg calcite per mm(2) of pellet at 713 cm(-1), 3.6 x 10(-4) mg aragonite per mm(2) of pellet at 700 cm(-1), 1.8 x 10(-4) mg aragonite per mm(2) of pellet at 713 cm(-1) and 3.1 x 10(-4) mg vaterite per mm(2) of pellet at 745 cm(-1). Analysis of a known ternary mixture of calcium carbonate polymorphs tested the validity of the method.