Determination of Concentrations of Solutes in Gaseous, Liquid, and Supercritical Co₂by Means of UV Raman Spectroscopy

Abstract

We measured compositions of high-pressure CO 2 solutions in vapor, liquid, and supercritical phases by means of UV-Raman spectra. Our goal was to investigate whether excimer-based Raman could quantitatively determine compositions of such solutions under high-pressure conditions. Some potential problems include (a) species that can absorb much, or all, of the UV-laser light, (b) fluorescence that might overwhelm the Raman signal, and (c) density gradients that would bend the laser beam. We studied two binary systems that were chosen to avoid such problems and that yielded quantitative composition analyses. These were (a) two-phase mixtures of CO 2 and n-pentane and (b) solutions of 1,1,1,2,3,4,4,5,5,5-decafluoropentane in CO 2 . We suggest some changes that could increase the usefulness of the method for future applications.