Multi-element determinations in foods from Amazon region by ICP-MS after enzymatic hydrolysis assisted by pressurisation and microwave energy

The use of pressurised solvents (liquids at a high pressure and/or high temperature without reaching the sub-critical point) or microwave energy were investigated to accelerate enzymatic hydrolysis processes of selected foods (Brazil nut, golden berries, acai fruit and heart of palm) from Amazon region for multi-element determinations. The target elements (Ca, Co, Cu, K, Mg, Ni, P and Rb) were released from dried and defatted foods by the action of a protease and an enzyme activator (DTT, dithiothreitol), and they have been evaluated by inductively coupled plasma - mass spectrometry (ICP-MS). The influence of variables inherent to the enzymatic activity (TRIS-HCl concentration, TRIS-HCl volume, pH, temperature, and protease XIV and DTT masses) and factors affecting pressurisation and/or microwave extraction (pressurised time, pressure and microwave extraction steps) on the efficiency of metals leaching were evaluated using a Plackett-Burman 28 × 3/32 experimental design as screening method. Results shown statistical significance for extraction temperature and TRIS-HCl concentration (confidence interval of 95%) for enzymatic extraction assisted by solvent pressurisation, whereas number of microwave extraction steps and DTT mass have affected enzymatic extraction assisted by microwave energy. After significant variables optimization, extraction procedure times were 7 min (7 min per sample) and 70 min (12 min per sample) for enzymatic extraction assisted by pressurisation and microwave energy, respectively. Limits of quantification were found to be from 1.2 ng g− 1 to 53.8 μg g− 1 and 0.23 ng g− 1 to 35.1 μg g− 1 for enzymatic extraction assisted by pressurisation and microwave energy, respectively. Repeatability of the over-all procedures were generally below 20%. Element contents in Amazon samples were within the 80-1400, 0.03-3.0, < 0.58-50, 500-25,000, 60-7480, 0.40-11.0, 70-14,000, 0.4-200 μg g− 1 ranges for Ca, Co, Cu, K, Mg Ni, P and Rb, respectively.