Development of a wide bore flow through microwave digestion device for thedetermination of trace metals in soil

A flow through microwave digestion device has been developed for the determ ination of Cd, Cr, Mn, Ni and Pb in soil by aqua regia extraction. This dev ice differs from existing commercially available devices as it uses a doubl e pumping action to replace the back pressure regulator traditionally used to achieve internal pressurisation. An acid front has also been included to overcome problems associated with the dilution of acid in samples due to d ispersion. Recoveries between 95 and 105% of certified values were achieved with standard deviations of less than 4% for certified reference soil (BCR 143R). A sample throughput of 6 samples per hour was achieved in the optim ised system. The performance of the device was tested by digesting real soi l samples ground through a 250 mu m sieve and slurried without the use of s urfactants. A comparison of analytical performance for analysing real sampl es was made between the microwave flow method and a thermal method.