Efficiency of oxidation in wet digestion procedures and influence from the residual organic carbon content on selected techniques for determination of trace elements

The efficiency of oxidation in wet digestion procedures for organic materials can be of great importance for the quality of the analytical data of various measurement techniques. Four items of commercial equipment for pressurised sample digestion were compared and it could be shown that the residual carbon content achieved only depends on the temperature of the digestion solution and not on the equipment, if the digestion time is long enough to reach the steady state. The consumption of nitric acid during the digestion procedure was investigated. This is important to consider, because the signal response of instrumental element determination can be influenced by the acid concentration of the sample solution. The relation between sample amount, maximum digestion temperature and residual carbon content in a closed vessel digestion system was depicted and the influence of incomplete oxidation of organic sample matrix on the determination of As and Se by means of axial ICP-OES was investigated.