A new method based on extraction induced by emulsion breaking for determination of Co and Ni in chocolate bars by graphite furnace atomic absorption spectrometry.

This paper describes a new experimental configuration of extraction induced by emulsion breaking method to extract and determine Ni and Co in chocolate bars by graphite furnace atomic absorption spectrometry. At optimized conditions, the sample (0.08 g) was mixed with 4 mL of extractant solution (4% m/v Triton X-100 and 10% v/v HNO3) in a plastic syringe to form a solid-oil-water emulsion. Then, emulsion breaking was assisted by membrane filtration. The total extraction procedure took approximately 1 min, in opposition to 25 (centrifugation) and 50 min (heating). Extraction yields ranged from 94.8 to 114.3% for Co and from 85.9 to 108.4% for Ni. The limits of detection and quantification were, respectively, 24.73 and 82.45 µg Kg-1 for Co and 49.05 and 163.5 µg Kg-1 for Ni. Recoveries ranged from 92.1 (Ni) to 105.4% (Co).