Microwave Extraction

The evolution and development of microwave technology for extraction of organic compounds from (semi)solid matrices is reviewed. After clarification of the terminology that encapsulates this approach, this chapter investigates the following key areas: the principle of microwave heating and differences from conventional heating; generic instrumentation including magnetron, wave guide, resonance cavity, and power supply; factors affecting microwave extraction including choice of organic solvent, sample size, microwave power, and extraction time; typical operating conditions based on US Environmental Protection Agency methods; standard methods are summarized and novel developments are explored in terms of the use of heat transformer disks with nonpolar solvents, microwave-assisted Soxhlet extraction and online systems for automating sample preparation prior to chromatographic analysis; a mini-history of the popularity of the approach with respect to sample types is considered; and the commercial suppliers of instrumentation are identified.