Environmental Sample Cleaning and Extraction Procedures by Microwave-Assisted Process (MAP) Technology

Abstract

Extraction is one of the most important sample preparation techniques in trace organic analysis. Very often for solid particulate samples, the method of choice is either liquid or gas extraction, i.e., extraction in a Soxhlet apparatus or in dynamic headspace. Soxhlet extraction is more popular than headspace analysis. The technique, however, has a number of drawbacks, since it is tedious and restricted in solvent selectivity. Samples are normally extracted at the boiling point of the solvent for a long period of time and the possibility of thermal decomposition of target compounds cannot be ignored. A further disadvantage of Soxhlet extraction is that a concentration/evaporation step is required, and it can introduce a high degree of contamination into the sample with solvent impurities. These problems, together with the rising cost of solvent and waste disposal restrictions, have led to the search for new techniques for sample extraction. Recent innovative processes,such as supercritical fluid extraction (SFE) and the microwave-assisted process (MAP) are very promising techniques. SFE has currently been developed and used, but it has technological drawbacks. The MAP technique has the potential for many applications in analysis. Comparisons of the results for sample preparations between MAP and conventional Soxhlet procedures are illustrated.