A system for detecting the presence of contaminants in a flowing stream of supercritical fluid. A sample stream is removed from a flowing stream of supercritical fluid as it exits the cleaning chamber (12) through an exit port (16), and is introduced into a second chamber (22). The sample stream is subjected to reduced pressure in a contaminant measurement zone (24). The supercritical fluid turns into gas (as represented by lines 30) at the reduced pressure with the contaminants remaining in a non-gaseous form. An attenuated total reflectance plate (36) is used to spectrophotometrically detect the presence of the non-gaseous contaminants which deposit on the surface (48) of the plate within the contaminant measurement zone (24). The system is useful for spectrophotometrically detecting the presence and identity of contaminants in supercritical fluids and is useful in monitoring both cleaning processes and extraction processes.
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