Closed vessel microwave-assisted wet digestion with simultaneous control of pressure and temperature in all vessels

A novel system for microwave-assisted wet digestion in closed vessels is described. Six pressure vessels made of quartz or Hostaflon^? TFM are placed in a special rotor in a microwave oven. During sample decomposition the pressure and temperature are measured in each vessel, and the data are transferred from the rotor by means of infrared light to the control unit. This means that no pneumatic or electronic connections to the vessels need to be established, providing very easy handling. The temperature history of each vessel is recorded; so the progress of each sample digestion may be reconstructed later on. Thus the requirements for quality control in sample digestion are available for the first time. For sample digestion at 75 bar and up to 280° C, quartz vessels with 50 mL volume are used. Depending on the matrix, the maximum sample loading capacity is 1.2 g. TFM-vessels with 100 mL volume work at 30 bar up to 240° C. The performance of the digestion system was tested with twelve standard reference materials. The results closely matched the certified values. Received: 18 September 1997 / Revised: 3 November 1997 / Accepted: 6 November 1997