Feasibility of microwave-induced combustion for trace element determination in Engraulis anchoita by ICP-MS

A method based on microwave-induced combustion (MIC) was developed for fish (Engraulis anchoita) digestion and subsequent determination of As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Se, and Zn by inductively coupled plasma mass spectrometry (ICP-MS). A reflux step (5 min) was applied to improve absorption and recovery of analytes. Nitric acid was investigated as absorbing solution and suitable results were achieved using 5 mol L⁻¹ HNO₃. Microwave-assisted digestion in closed vessels using concentrated HNO₃ was also evaluated for comparison of results. Both sample preparation methods were considered suitable for sample digestion but MIC was preferable not only because diluted HNO3 can be used as absorbing solution but also because it provides higher efficiency of digestion and also better limits of detection. Accuracy was evaluated by the analysis of certified reference materials (DORM-2 and TORT-2) after MIC digestion with subsequent determination by ICP-MS. Agreement with certified values was better than 94%.