Direct Analysis of Cocoa Powder, Chocolate Powder, and Powdered Chocolate Drink for Multi-element Determination by Energy Dispersive X-ray Fluorescence Spectrometry

Abstract

The aim of this study was to evaluate the potential of applying energy dispersive X-ray fluorescence (EDXRF) spectrometry to determine Ca, K, P, Mg, Fe, Zn, Cu, Mn, and Al concentrations for direct analysis of cocoa powder, chocolate powder, and powdered chocolate drink samples. The proposed method was calibrated using samples previously analyzed by inductively coupled plasma optical emission spectrometry (ICP OES). For comparison purposes, the samples were also analyzed by ICP OES after an acid digestion procedure, and no significant differences were observed between the concentrations determined by EDXRF when compared to those by ICP OES. The coefficients of correlation (R) from the calibration curves and the limit of quantification (mg kg−1) were Ca (0.996, 0.030), K (0.985, 68), Mg (0.974, 0.020), P (0.986, 0.50), Mn (0.998, 3.6), Fe (0.981, 2.5), Cu (0.978, 1.3), Zn (0.996, 0.80), and Al (0.983, 7.5). The precisions obtained for the elements were between 1.5 and 7.8% (n = 7), indicating that the preparation of the pellets was efficient to perform analysis by EDXRF. Potassium was the macro-mineral with higher concentrations in the samples. In relation to the micro-minerals, Fe had the greatest concentration. Significant concentrations of Al were also found. It was found that, in general, samples of chocolate powder and powdered chocolate drink may be considered good sources for the ingestion of Mg, Mn, Ca, K, P, Fe, Zn, and Cu.