Note: Microwaves are electromagnetic radiation of \(\pu{300\!{–}\! 300,000 MHz}\). They heat the extraction solution by their interaction with dielectric compounds (solvent or sample). Microwave heating is more efficient and rapid than convection and conduction and enhances the migration rate of compounds into the extraction solvent. Microwave-assisted extraction may be performed in a closed vessel with control of temperature and pressure or in an open vessel at atmospheric pressure.