QUANTITATIVE-ANALYSIS BY ONLINE SUPERCRITICAL FLUID EXTRACTION FOURIER-TRANSFORM INFRARED SPECTROMETRY

A system is described wherein the supercritical fluid extracts of compounds can be analyzed on-line by FT-IR without prior chromatographic separation. Al-m- X 0.010-in.4.d.stainless steel transfer line was used between the extraction vessel/system cryotrap and the high-pressure IR flow cell. Extraction can be directly conducted as static, dynamic, static-dynamic, or dynamic-cryotrap with minor system alterations. Quantitation was performed by integrating the ares of the extract plug, plotted in terms of detector signal versus time. The system was perfected for the extraction and quantification of n-tetacosane (C24) from Celite, but has subsequently been applied to more complex systems, such as tiber/fabric oils, with comparable success. The detection limit for C24 by on-line SFE/FT-IR was calculated to be 74 ng. The relative speed and reproducibility of the method make it a viable alternative to the liquid extraction/IR methods used in industrial process analysis that require increasingly EPA-regulated solvents.