COMPARISON OF THE EFFICIENCIES OF ONLINE AND HIGH-PRESSURE CLOSED VESSEL APPROACHES TO MICROWAVE HEATED SAMPLE DECOMPOSITION

Two microwave heated digestion techniques have been tested with a view to the evaluation of the effectiveness of wet decomposition procedure s: a high-pressure/temperature focused microwave heated and an on-line microwave heated system. The efficiency of decomposition was studied using a number of biological reference materials as well as urine and sewage plant effluent. Oxidation reagents included mixtures of nitric acid, nitric acid/hydrogen peroxide and peroxodisulphate (''Oxi-solv'' ). The residual carbon content of the digestate was determined coulome trically. Pressurised decomposition of a TFM-Teflon vessel is the most effective procedure (organic material is totally oxidised with nitric acid in a single-step procedure), whereas urine and sewage plant effl uent are incompletely decomposed with on-line microwave heated digesti on.