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Microwave- assisted digestion of organic materials with KClO3/ HNO3 for the analysis of trace metals and non-metals

M.Sager

A new microwave assisted pressure bomb digestion method employing an almost saturated potassium chlorate solution acidified with nitric acid, has been introduced for the digestion of plant and food samples, which permits to use up to 4 times the usual sample weight within some shorter time. The digest is especially suitable for the analysis of non- metals (boron, silicon, germanium, total sulphur, iodine), but also for other trace elements likeAl- Ba-Be-Cd-Co-Cr-Cu-Fe-Li-Mn-Mo-Ni-Pb-Sb-Sn-Tl-V-Zn, aswell as formain elementsCa-Mg-Na-P after dilution. For ICP-OESmeasurements, calibrants have to be matched with the same amount of digestion solution. ICP-MS measurements were done after dilution and addition of internal standard indium. ICP-OES determination of iodine determination is interfered by phosphorus, and could be done in the ICP-MS by standard addition as the iodate. Due to saltmatrix and blanks, K and Cl, as well as Rb and Br, cannot be determined, whereas blanks for B and Si are lowered. In the ICP-MS, the isotopes V-51, Cr-52, As-75, Se-77 and Mo-95 are positively interfered. Arsenic can be determined by hydrideAAS. The digestion efficiency versus some aromatic compounds may be lower than from concentrated HNO3, therefore intermediate degradation products of phenylalanine, tyrosine, and salicylic acid were studied in detail. The proposed method was checked in ring tests of various plant and food samples.