Micro-Scale Methods for Characterization of Supercritical Fluid Extraction and Fractionation Processes.

摘要

The development of new supercritical fluid extraction and fractionation processes requires exploration of wide ranges of fluid temperature and pressure. As the fluid phase composition becomes more complex, conventional methods become inadequate unless augmented by increasingly sophisticated analytical instrumentation. In addition to chemical complexity, analysis is often hindered by characteristics of the analyte which make supercritical fluid extraction desirable (e.g., high molecular weight or thermal lability). Micro-scale methods are described which address these problems while providing the additional benefits of speed, reduced cost, greatly reduced sample and solvent consumption, and safety. Techniques are described in which the fluid phase from micro-scale (0.005-5 ml) high pressure cells is sampled and analyzed in either continuous or periodic modes. The methods developed in our laboratory utilize capillary supercritical fluid chromatography and direct fluid injection-mass spectrometry (or their combination), in addition to conventional analytical techniques, for the characterization of complex supercritical fluid mixtures. The application of these methods to various extraction and fractionation processes involving C02 and NH3, solubility studies of simple and complex mixtures, and the study of rapid chemical processes in supercritical water is described. New methods for the automated examination of extraction processes using capillary chromatography are also described and their initial application illustrated.