Determination of calcium carbonate in limestone by attenuated total reflectance Fourier transform infrared spectrometry

Attenuated total reflectance Fourier transform infrared (ATR/FT-IR) spectrometry was applied to the determination of calcium carbonate in limestone. Both of the simple and multiple linear regression methods have been investigated. The correlation coefficient was found to be increased to 0.985 when the multiple linear regression analyses using the absorbance values at all of the wavelengths were applied. The standard deviation of calibration for 37 samples by this method was 0.601. In order to test the applicability of the multiple linear regression method to routine analyses of limestones, 31 samples collected from the various mines distributed in Korea were analyzed by chemical and ATR/FT-IR methods. The range of CaCO3 concentrations of the tested samples were 86-97%. The standard error of prediction (SEP) was found to be 0.294 when the absorbance values at all of the three wavelengths were used, whereas the SEP values were 1.340, 1.072 and 0.961 for the wavenumbers of 711, 1406 and 875 cm(-1), respectively. The results indicate that the ATR/FT-IR method can be applied to the routine determination of CaCO3 in limestone by mid-infrared spectroscopy. The present method required virtually no pretreatment procedure and thus took less time comparing with the conventional wet chemical methods.