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, α, 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 Beerʹs law was developed. The detection limits were also established and found to be 1.1×10−4 mg calcite per mm2 of pellet at 713 cm−1, 3.6×10−4 mg aragonite per mm2 of pellet at 700 cm−1, 1.8×10−4 mg aragonite per mm2 of pellet at 713 cm−1 and 3.1×10−4 mg vaterite per mm2 of pellet at 745 cm−1. Analysis of a known ternary mixture of calcium carbonate polymorphs tested the validity of the method.