A variable restrictor, also known as a Back Pressure Regulator (BPR) is a key component in the successful application of supercritical fluid technology. You will note that all of our products have this key component. The restrictor valve allows for the controlled and metered release of the pressure built up in the sample vessel into the collection assembly. Materials that have been solubilized in the SCF CO2 can now be collected at atmospheric pressure. Beyond the metering out of the flow, the restrictor valve assembly also compensates for the Joule-Thompson cooling that occurs through expansion of pressurized CO2 by adding heat to the assembly. The heating ensures that the valve will not freeze and solubilized analytes precipitate plugging this valve.