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Supercritical extraction is a separation method for solutions involving the use of supercritical fluids. These fluids are brought to a state of such high heat and pressure that they act both like a gas and a liquid and no longer undergo phase changes. Carbon dioxide is a popular material for this process, although other compounds can be used as well. There are some advantages to supercritical extraction that make it useful for a range of applications, although it can also be expensive to perform, which is a limitation.
In this procedure, technicians bring carbon dioxide or another materials to a supercritical point and allow it to flow into an extraction chamber. This acts as a solvent to separate the constituents of a mixture. For example, a company could use supercritical extraction to draw caffeine out of coffee with minimal changes to the coffee itself to address concerns about flavor and integrity.
One advantage to this technique is that it is environmentally friendly. The solvents are not dangerous, and in the case of carbon dioxide and many other compounds, changing the temperature allows the solvent to dissipate into a trap so it does not contaminate the finished product. Trapping allows companies to reuse the material repeatedly, which reduces demand for solvents and prevents their release into the environment.
This method is also much faster than other methods used for extraction. Supercritical extraction can take less than an hour, in contrast with hours or sometimes days required by other methods. This can compensate for the increased expense associated with setting up a system capable of supercritical extraction. The equipment needs to be capable of attaining and holding high heat and pressure throughout the process for stability and consistency, and this can be costly to implement.
It is possible to adjust the end products by varying the pressure. This allows companies to control what they extract using this method; in essential oil processing, for example, the technicians can lift some lipids and not others. The high control available with supercritical extraction can make it useful for activities like processing scientific samples or producing products of very high purity.
Industrial production is one application for supercritical extraction. It can also be used to prepare and test samples in lab environments like forensic and research facilities. The equipment for these applications can be smaller, as technicians do not need to process high volumes of material.