Focused microwave-assisted digestion of biological reference materials for the determination of trace metals by ICP-MS

A rapid method for the preparation. of biological materials based on their digestion in a low power-focused microwave system prior to ICP-MS was developed. The samples were decomposed using a three-step attack with 30% nitric acid at (a) 30 W for five minutes, (b) 50 W for six minutes, and (c) 80 W for six minutes. This was followed by cooling the mixture and subsequently attacking with a 15% solution of hydrogen peroxide at 30 W for five minutes. The resultant solution was diluted with 2% nitric acid and aspirated to the nebulizer. Eight elements (Mg, Mn, Ni, Cu, Zn, As, Sr, and Cd) were determined simultaneously using the peak hopping mode and external calibration of the ICP-MS. The method was validated by the analysis of four NRCC reference materials: LUTS-1 and TORT-1 (lobster hepato-pancreas), DORM-1 (dogfish muscle), and DOLT-2 (dogfish liver).