Chromatograph having pneumatic detector

Abstract

A chromatograph includes an injector for receiving a sample and a pressurized carrier fluid flow and in response providing a sample/fluid mixture; a separation column located in a temperature-controlled zone for receiving the sample/fluid mixture and for providing a column effluent stream; a pneumatic detector having an orifice for receiving the effluent stream; means for sensing the volumetric flow rate of the fluid mixture entering the column and for generating a respective flow rate signal; means for sensing the column input pressure and generating a respective input pressure signal; an electronic pneumatic controller including means for receiving the flow rate signal and input pressure signal and for controlling in response the input pressure and the volumetric flow rate of the carrier fluid; and means for detecting a change in the pressure of the effluent stream at the orifice in response to a change in the density of the effluent stream passing through the orifice and for generating a representative output signal, whereby one or more characteristics of the effluent stream that are related to the density of the effluent stream are represented by the output signal. The temperature of the temperature-controlled zone, and some or all of the input and output pressures and the carrier fluid volumetric flow rate are controlled by the electronic pressure controller, which reduces unwanted flow rate variation in the fluid stream that is subject to detection is greatly reduced. The sensitivity of the pneumatic detector to such unwanted flow rate variations is thus mitigated by the operation of the electronic pneumatic controller.

Dependencies are inferred from the claim text.