CHEMOMETRIC OPTIMIZATION OF OXYGEN FLASK COMBUSTION FOR CADMIUM DETERMINATION IN CHOCOLATE BY GF-AAS

Abstract

Cadmium is a toxic trace element that may accumulate in cocoa-derived products, requiring reliable methods for its determination. Oxygen flask combustion (OFC) was optimized as a sample preparation technique for cadmium determination in chocolate by graphite furnace atomic absorption spectrometry (GF-AAS). Response surface methodology was used to evaluate the effects of sample mass, oxygen flask volume, and absorbing solution volume on cadmium recovery. Despite relatively high variability within the optimization set, suitable conditions were identified: 75 mg sample, a 500 mL oxygen flask, and 12.5 mL of 1 mol L⁻¹ HNO₃ as absorbing solution. Under these conditions, a mean recovery of 90.2 ± 5.2% (mean ± SD, n = 3) was obtained for SRM 2384, with reduced reagent consumption and simpler sample preparation compared with conventional acid digestion. The optimized procedure was applied to 18 commercial chocolate samples from four manufacturers. Cadmium concentration showed a significant positive correlation with cocoa content across the complete dataset, while differences among product series indicated that additional factors, including cocoa origin and product characteristics, may also influence cadmium levels. The OFC-GF-AAS procedure provides a simple and cost-effective alternative for cadmium determination in chocolate.