Near infrared thermal lens spectrometry for the real-time monitoring of supercritical fluid extraction

A commercially available supercritical fluid extractor provided with carbon dioxide was coupled to a dual-beam thermal lens spectrometer with a pumppr obe coaxial cofiguration, pumped by a pulsed Nd-YAG laser operating at the fundamental wavelength of 1064 nm. As a preliminary step, several compounds were studied in batch regime using carbon tetrachloride as solvent, in ord er to observe the influence of overtones and combinations involving distinc t chemical bonds on thermal lens spectrometry (TLS). Several factors relate d with supercritical fluid extraction (SFE) under hydrodynamic conditions w ere studied in order to establish their influence both in the extraction yi eld and thermal lens signal magnitude obtained. The advantages and limitati ons of the hyphenated SFE-TLS technique proposed are discussed, and the pos sibility of on-line detection in SFE with a pulse thermal lens spectrometer was demonstrated. (C) 1999 Elsevier Science B.V. All rights reserved.