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.