This paper reports the design of a simple and inexpensive optical fiber capillary flow cell which is ideally suited to Raman spectroscopy and, in particular, the analysis of high-pressure supercritical fluid solutions. Light is delivered directly to the solution by use of optical fibers which run along the bore of the capillary. For maximum efficiency of light collection, the capillary is mounted directly onto and along the axis of the entrance slit of a dispersive Raman spectrometer. The Raman spectra of supercritical carbon dioxide (scCO2) solutions of gases (e.g., nitrogen and hydrogen), and solid solutes (e.g., naphthalene) are presented.
Steven M. Howdle, Keith Stanley, Vladimir K. Popov, and Viktor N. Bagratashvili, "Can High-Pressure Raman Spectroscopy Be Simplified? A Microscale Optical-Fiber Capillary Cell for the Study of Supercritical Fluids," Appl. Spectrosc. 48, 214-218 (1994)