Evaluation of a high-pressure, high-temperature microwave digestion system

Abstract

A high-pressure, high-temperature focused microwave digestion system was evaluated and compared with a conventional, closed-vessel digestion system. A suite of 18 test elements was determined in six Standard Reference Materials (Peach Leaves, Orchard Leaves, Oyster Tissue, Bovine Liver, Bituminous Coal, and River Sediment) by inductively coupled plasma atomic emission spectrometry and electrothermal atomic absorption spectrometry. Observation of the graphite furnace background absorbance for the digestates, and their high-performance liquid chromatograms, demonstrate that the high-pressure, high-temperature system results in a more complete destruction of the sample matrix. The high-temperature system also shows higher accuracy for the test metals in the reference materials (average error 7.1%) than the conventional system (11.8%). Finally, the high-temperature system has a per-sample analysis time (7.5 min) that is 10 min faster than the conventional system. On the negative side, the high-temperature system is not capable of monitoring temperature during a digestion program. As a result, vessel rupture is common during method development. This results in complete destruction of the vessel, and the emission of potentially dangerous exhaust fumes into the laboratory environment.