Abstract:
To collect analyte in a supercritical fluid extraction process, the extractant flows to a collection container (130) under pressure. In one embodiment, the collection container (130) contains collection solvent (144) through which the extractant flows to partition analyte. The extractant adds to the liquid and when the collection solvent-extractant mixture rises to a heating zone, the extractant vaporizes selectively since its vapor pressure is higher than the vapor pressure of the collection solvent (144). When its pressure exceeds a preset valve (148) pressure it is vented so that extractant continually leaves the collection container (130). After the extraction is complete, the analyte is concentrated in the collection solvent (144). In another embodiment, the collection vessel includes a solid material on which the analyte collects. It is removed under pressure by a solvent that is concentrated under pressure.
Abstract:
An apparatus for supercritical fluid extraction incorporates a removable extraction cartridge which in operation has insignificant pressure difference between its inside and outside walls. Because of the low pressure difference, the extraction cartridge need not have the strength to withstand significant pressure and can be made out of molded plastic for disposable use as well as stainless steel and/or machined plastic for reusability. The extraction cartridge can be removed and opened for sample access without the use of tools. The outside of the cartridge can be purged after it is installed in a heated high pressure vessel to remove contamination from its exterior. In one embodiment, the extractor includes a fraction collector for extractants, an automatic sample changer and an automatic cartridge transfer mechanism which provide completely automated extractions.