Study of the Interactions between Sucrose and Metal Ions (Mg 2+ and K + ) and Their Simultaneous Quantification in Ternary Mixture by Mid-Infrared and 13 C Nuclear Magnetic Resonance Spectroscopies

Abstract

In this paper, a ternary aqueous mixture of sucrose and two metal ions (Mg²⁺ and K⁺) has been examined by mid-infrared spectroscopy coupled with principal component analysis (PCA) and the partial least-squares regression method (PLS). PCA was first used for the description of Fourier transform mid-infrared (mid-FTIR) spectral data of the complex samples. The resulting factorial map, set up with the two most influential component axes, features distinct concentration distribution specific to each component. Prediction equations that linked sucrose, magnesium, and potassium concentrations to the spectral data were established by the partial least-squares regression method. A quite good correlation was obtained between the first 5 axes and the concentration variables, with coefficient values ranging from 0.984 to 0.997. It was thus possible to predict specifically both metal ion concentrations in the ternary mixture with relatively good accuracy. The ternary mixtures of sucrose, Mg²⁺, and K⁺ were also subjected to ¹³C NMR (nuclear magnetic resonance) analysis. From the relative displacements of chemical shifts of the carbon atoms of sucrose, it was possible to determine the influence of each metal ion present in the mixture.