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

Abstract

A flow through microwave digestion device has been developed for the determination of Cd, Cr, Mn, Ni and Pb in soil by aqua regia extraction. This device differs from existing commercially available devices as it uses a double 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 dispersion. 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 optimised system. The performance of the device was tested by digesting real soil samples ground through a 250 μm sieve and slurried without the use of surfactants. A comparison of analytical performance for analysing real samples was made between the microwave flow method and a thermal method.