Applications of FTIR Spectroscopy to Supercritical Fluid Drying, Extraction and Impregnation

INTRODUCTION

Most applications of infrared (IR) spectroscopy deal with samples in one of the three states of matter: gases, liquids and solids. In this context, IR spectroscopy of liquefied or high-pressure gases has never been considered as a study of a distinct state of matter. The term “supercritical fluid” has been used so frequently in the past few years that it could imply, to some inexperienced readers, that one is dealing with a state of matter which is neither gas nor liquid. However, if a supercritical fluid (SCF) is defined as a substance above its critical pressure and temperature, there is still no distinction between a highpressure gas and an SCF because, under all circumstances, such a fluid will occupy the full volume of its container, demonstrating behavior typical of a gas.