A number of choices are available for the extraction of compounds from solid matrices. Whether the task is to look for desired compounds or unknown concentrations of toxic contaminants, the overall goal is achieved by using a solvent to remove the compound from the matrix. Traditional techniques such as soxhlet and sonication use large amounts of solvent to achieve good extraction efficiencies, and soxhlet extraction times range from six to twenty-four hours.
Newer technologies such as pressurized solvent extraction systems were developed to reduce the time spent on the extraction and the amount of solvent consumed. These systems gained interest with improved productivity in a contract lab setting but also in research labs looking to develop new areas of application. The drawback to these pressurized systems was largely based in price, ease-of-use, and the sequential nature of the extraction set-up.
Microwave extraction has been used for a number of years to extract compounds from plastics, food and animal feed, biological, and plant samples. With the same advantages of extraction speed and reduced solvent consumption, microwaves became very popular for a broad number of applications. But for the technology to have real traction, two critical things happened that have launched a high interest in this technology today: the capability of parallel processing and the promulgation of microwave extraction by the US Environmental Protection Agency (US EPA Method 3546) for the extraction of solid matrices in January of 2008. With the regulated method and a clear return on investment by running more than 20 samples in a single batch, the environmental contract lab industry embraced this technology as a new productivity tool.