Destruction of organic materials by pressurized microwave digestion

Summary

This paper describes the utility of pressurized microwave digestion (up to 85 bar) for a broad spectrum of organic materials (blood, urine, milk powder, tissues). The “quality” of the sample solution was tested by the determination of Pb, Cd and Cu (additionally Ni and Co in some of the matrices) by anodic stripping voltammetry (DPASV) and Hydride Generation AAS (HAAS) for As. It is clearly shown that no universal “cooking recipe” can be given. The necessary oxidation potential is very dependent on the type of organic matrix and therefore the use of acid combinations (HNO₃/HClO₄/H₂SO₄) is generally necessary to obtain adequate solution of the sample. In some cases the power of the microwave oven was not high enough to digest two samples simultaneously. (Significant differences in the ease of solution are shown in the digestion of one or two samples). Some important improvements for sample preparation, such as moistening the powdered material with water and mixing well with the acid used before closing the digestion vessel etc., are also given.