Extraction process that uses supercritical carbon dioxide (CO2) as the selective solvent. The polarity of CO2 limits its use to extractions of relatively apolar or moderately polar solutes. Thus, a small amount of a polar organic solvent (e.g. methanol, acetonitrile, water), called a modifier or entrainer, is usually added to the supercritical fluid for extraction of more polar compounds. CO2 is frequently used as the extraction solvent in super-critical fluid extraction because it is in a supercritical state at a relatively low temperature (31°C) and pressure (73 atmospheres), making it a suitable choice from an instrumental point of view. Extraction using supercritical CO2 also avoids the use of dangerous or toxic organic solvents and the gas is easily removed by reducing the pressure.