Final evaluation of US EPA method 3546: Microwave extraction, a microwave-assisted process (MAP (TM)) method for the extraction of contaminants underclosed-vessel conditions

Microwave-assisted extraction, a MAP (TM) technology, has been the subject of enhanced interest from the environmental sector in the last few years as a result of the need for methodologies that improve sample preparation wit hout compromising the quality of the data while being environmentally susta inable. Liquid-phase microwave-assisted extraction offers such advantages: it is a very fast extraction technique, it consumes less solvent and energy , and it is cost effective. A preliminary validation study involving closed -vessel apparatus and contaminants such as PAHs, PCDDs/PCDFs, chlorinated p esticides, and PCBs was performed (Li et al., 1996). Excellent performance and precision were achieved for these analytes (Li et al., 1996). In order to fully evaluate the method fora wider range of analytes an interlaborator y study was performed. A round-robin study was performed with five laborato ries carrying out the extraction portion. This study also involved thermall y labile and potentially reactive RCRA target analytes such as phenols, phe noxyacid herbicides, and organophosphorus pesticides. Three split samples w ere used by each laboratory using methodologies stipulated in a single stan dard operational procedure (SOP). The extractions from the five laboratorie s were sent to a single laboratory who performed all the analyses in order to minimize the variability of the results due to the determinative procedu re. Clean up was performed using standard procedures and analyses were done according to the appropriate US EPA SW-846 methods. The broad range of app licability, the reduced sample preparation time, and the reduced amount of solvent used all contribute to achieving sustainable environmental protecti on goals. Furthermore, the reduced operational costs associated with the pr otocol - compared to conventional Soxhlet, for example-are significant and prove valuable in these times where the `greening" of the laboratory usuall y gives rise to higher operating costs. Further work involving open-vessel apparatus is under way.