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 t heir 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 mi nutes, and (c) 80 W for six minutes. This was followed by cooling the mixture and subsequently attacking with a 15% solution of hydrogen per oxide at 30 W for five minutes. The resultant solution was diluted wit h 2% nitric acid and aspirated to the nebulizer. Eight elements (Mg, M n, Ni, Cu, Zn, As, Sr, and Cd) were determined simultaneously using th e 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 D OLT-2 (dogfish liver).