[Microwave extraction technique].

Abstract

A new microwave aided extraction (MAE) technique is introduced in this paper. It gives the extraction method as well as reagents, equipment and conditions used in the technique. In temperature controlled pressurized vessels, polar solvent (eg. acetone) and the combinations of polar and non-polar solvents can be heated to approximately 100 degrees C above their normal boiling points. It is told that the higher the extraction temperature the more the recovery is. The ratio of polar to non-polar solvents affects not only the microwave heating rate but also the extraction recovery. The highest recovery ratios are gotten at the solvent ratio of three parts of acetone to two parts of hexane. We can see from the pesticides chromatogram with MAE, that very little break-down of endrin or DDT are detected and they are well below the EPA specified tolerance limits. We can find from the comparison of MAE with sonication and Soxhlet extraction techniques that microwave extraction technique has not only higher average recoveries (%) but also good precision (RSD, %). The data and comparison results illustrate that the microwave extraction is a rapid method (about 15 minutes) with less solvent consumption (about 30-50 mL), good recovery, and easy to be controlled automatically in comparison with the Soxhlet extraction, sonication and other extraction methods.