Evaluation of an ultrasonic digestion procedure for total metal determination in sediment reference materials

In this work the possibility to use a simple and easily available laboratory device—routine ultrasonic bath—has been evaluated for total metal determination in sediments from different origin. The investigated instrumental parameters were time and temperature, whereas power was maintained constant set at 100% of nominal power. Four different sets of parameters were applied on a lake sediment reference material (RM), the results obtained for five elements—Cd, Cr, Cu, Ni and Zn—were statistically compared with those obtained by a previously optimised microwave acid digestion procedure on the same material. The optimal set of parameters—30 min sonication at ambient temperature—was chosen, and then applied to other five sediment RMs from different origin. In this case four additional elements—As, Pb, V and Fe—were also determined and the results were compared with reference and microwave values.The results obtained by the ultrasound digestion procedure were higher than 80% of the reference and/or microwave values in 40 out of 44 cases. In any case, the results obtained by ultrasonic procedure were statistically comparable to reference values (mean of means of interlaboratory exercises or certified values) in the 84% of the cases.