Extraction Applications with Superheated Water

As the temperature of liquid water is raised under pressure, between 100 and 374 ºC, the polaritydecreases markedly and it can be used as an extraction solvent for a wide range of analytes. Most interest has been in its application for the determination of PAHs, PCBs, and pesticides from environmental samples, where it gives comparable results to Soxhlet extraction but more rapidly and without the use of significant volumes of organic solvents. Unlike SFE, n-alkanes are not extracted unless the pressure is reduced and steam is used. Other applications have included the extraction of essential oils from plant material where it preferentially extracts the economically more important oxygenated components compared to steam distillation. In many cases the superheated water extraction is cleaner, faster and cheaper than the conventional extraction methods.