Abstract: The present invention pertains to an apparatus for restricting supercritical fluid. The apparatus comprises an elastic tube through which the supercritical fluid flows. The apparatus also comprises means for adjustably compressing the elastic tube. The comprising means is in contact with the tube. Preferably, there is also means for facilitating flow through the tube. The facilitating means is in communication with the tube in proximity to the compressing means. In a preferred embodiment, the adjustable compressing means includes a first member having a first opening through which the tube extends. The first opening has a threaded portion. There is also a second member having a second opening through which the tube extends. The second member has a threaded shaft for threadingly engaging with the threaded portion of the first opening.