Preparation of cocoa flour reference materials and determination of cadmium content using GFAAS

In-house cocoa flour RMs instead of CRMs were prepared and checked for its homogeneity and stability. Due to CRMs limited availability in terms of matrices of concern and high production cost when making in-house cocoa flour, RMs are alternatively used for daily quality control in the laboratory. The analysis method for reliable checking of homogeneity and stability of cadmium content in the in-house cocoa flour RMs was studied. The effects of magnesium nitrate and lanthanum/magnesium nitrate as chemical modifiers in the determination of cadmium in cocoa flour by GFAAS were studied as well. Detection limit of the method was estimated to be 0.07 μg L(calculated as 3Sy/x/slope of calibration curve) and calibration curve of working range was linear. The results analysis of candidates for in-house cocoa flour RMs revealed consistent results and no variability between and within-bottle was observed at 95% limit of confidence and stability during the period of time observed.