The development and characterization of a supercritical state chromatographic system with a new micro adsorption detector

The use of fluids above their critical temperatures and pressures in chromatography offers many intriguing possibilities. Supercritical fluid chromatography (SFC) combines some of the advantages of both gas and liquid chromatography. High molecular weight compounds can be separated rapidly by utilizing SFC. A complete system for SFC is described. The system employs a metering pump, relief valve, damping device, constant pressure regulator, sample injection valve, oven, flow controller and a heat of adsorption detector. The detector is composed of multi-thermocouples (thermopile) with a suitable adsorbent embedded in one end which becomes the hot junction, and the opposite end serves as the cold junction. The temperature changes resulting from the heats of adsorption and desorption of compounds eluted from the column are measured. The detector is unique in that by the proper selection of the mobile phase and the absorbent all substances separated can be detected making it of universal application. The maximum sensitivity of the detector for samples passing through the average column is in the submicrogram range. The operation of the SFC system is demonstrated by showing several examples of separations and detections. The relationship of detector sensitivity to flow rate is also discussed.