Direct determination of minerals in human diets by infrared spectroscopy and X-ray fluorescence

Abstract

The use of near and mid infrared spectroscopy and X-ray fluorescence (XRF) to determine the concentration of mineral elements in Spanish human diets was investigated. Thirty-five commercial baby foods, 6 children fast food menus and 13 university canteen menu samples were analysed by infrared and XRF spectroscopy and spectra evaluated by using reference data obtained by inductively coupled plasma optical emission spectroscopy (ICP-OES). Models for calcium, potassium, iron, magnesium, sodium and zinc determination were built and validated. Spectra were pre-treated by using different pre-processing algorithms (multiplicative scatter correction, standard normal variation, first derivate, orthogonal signal correction, smoothing and mean centre) prior to developing calibration models using partial least squares and were evaluated by cross-validation and external validation. The highest coefficients of determination in validation (R2val) and the lowest relative root-mean-square error of prediction were obtained for potassium determination by MIR (0.86 and 11%), NIR (0.9 and 11%) and XRF (0.9 and 10%).