Enzymatic digestion and ultrasonication:: a powerful combination in analytical chemistry

The physico-chemical forms in which the heavy metals occur in the environment, particularly in biological samples, may strongly condition their bioavailability and toxicity. Hence, the distinction between different fractions of the total metal is of interest. Today, the challenge facing the scientific community and regulatory agencies is to assess health risks and/or benefits of low-level exposure to metals and metalloids in the environment, especially in foods. Accordingly, new analytical procedures to enable determination of trace and ultratrace levels of metals/metalloids and their species are needed so that the steps of extraction and separation must be mild enough to liberate the species from the matrix while maintaining their chemical integrity. The combination of enzymatic digestions plus ultrasonication, by either bath or probe, has recently emerged as a promising methodology for metal/metalloid speciation with environmentally acceptable performance. We critically review the state-of-the art of enzymatic digestion in sample treatment for total metal determination and speciation by atomic spectrometry. In addition, we comment on new trends based on the capability of novel sample treatments using enzymes and ultrasonication. We also provide guidelines to implement this analytical methodology in the laboratory. (C) 2004 Elsevier Ltd. All rights reserved.