Determination of aluminum, copper and manganese content in chocolate samples by graphite furnace atomic absorption spectrometry using a microemulsion technique

Chocolate is a complex sample with a high content of organic compounds, and its analysis usually involves digestion procedures that could pose the risk of sample loss and contamination. In this study, microemulsions were used to determine trace metals in chocolate samples by graphite furnace atomic absorption spectrometry. This method is simpler and requires fewer reagents than other sample pre-treatment procedures. Furthermore, the calibration can be carried out using aqueous standards. The microemulsion, which used Tween 80 as a surfactant, was prepared by a conventional method that involves heating and mixing the constituents. The microemulsion stabilization included magnetic stirring for 15 min at room temperature. Validation of the method for copper and manganese was performed against a baking chocolate standard reference material (SRM 2384) with recoveries of 98% and 108%, respectively, for the two elements. The use of microemulsions allowed the evaluation of these metals in real chocolate samples with adequate accuracy and minimal sample manipulation.