INDIRECT METAL ION (K⁺, NA⁺, MG²⁺, AND CA²⁺) QUANTIFICATION FROM INFRARED SPECTROSCOPY

ABSTRACT

In this paper, we report the use of Mid-FTIR spectroscopy coupled with Partial Least Squares method for the quantitative determination of various alkaline and alkaline earth metals in aqueous solution owing to their interactions with sucrose. First of all, prediction equations that linked cation concentration to the spectral data were established independently for each ion (K⁺, Na⁺, Mg²⁺ or Ca²⁺): very high correlation coefficient values between the two first axes and the chemical values were obtained. Moreover, a good prediction could be made whatever the nature of ion involved in interaction with sucrose. Then, all spectral data have been gathered for generating a common prediction equation. In this case, the predictions of metal ion concentration are almost as much accurate. For both regression models, Mg²⁺ appears to provide the best precision in quantification. Nevertheless, the different types of aqueous solution, regarding to ions, can be discriminated on the basis of their spectral data set up with the three mostly correlated axes of the PCA.

Keywords:

• Ion-sugar interactions
• Mid-FTIR
• Principal component analysis
• Partial least squares regression
• Principal component regression
• Quantification

ACKNOWLEDGMENTS

This work was supported by a grant from the Conseil Général and the Conseil Régional de la Réunion. Thanks for the anonymous referees for their critics and advises.