Multielemental quantification in dark chocolate by ICP OES

In the present work inductively coupled plasma optical emission spectrometry (ICP OES) method for quantification of macro and micro elements in dark chocolate was developed. The plasma characteristics have been evaluated based on simple diagnostics such as the Mg II 280.270 nm/Mg I 285.213 nm (Mg II/Mg I) line intensity ratio. The validation process of the developed method involved precision, accuracy, linearity of the calibration curve, detection (LOD) and quantification limit (LOQ). The method was validated with Certified Reference Materials (CRM). Precision of repeatability (CV) was under 8% for all elements and accuracy was above 93%. The proposed method was applied for the determination of 25 elements in dark chocolate samples. Mean concentrations in mg/kg for macro and micro elements were: 9380 (K), 2360 (P), 1390 (Mg), 1120 (Na), 660 (Ca), 106 (Fe), 58.2 (Si), 46.5 (Al), 23.3 (Zn), 14.2 (Cu), 13.3 (Mn), 7.0 (B), 6.5 (Sr), 6.2 (Sb), 6.1 (V), 5.4 (Ba), 3.2 (Ni), 1.5 (Li), 0.97 (Cr), 0.71 (Sn), 0.47 (Pb), 0.29 (Mo), 0.27 (Co), 0.11 (Se) and 0.10 (Cd). The daily consummation of dark chocolate contributes to the dietary intake of trace elements, mainly Cr, Cu and Fe.