Measurement of entrainer effects of water and ethanol on solubility of caffeine in supercritical carbon dioxide by FT-IR spectroscopy

Yoshio Iwai, Hirotaka Nagano, Gil Sun Lee, Machiko Uno, Yasuhiko Arai

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The solubilities of caffeine in supercritical CO2, supercritical CO2 + water, supercritical CO2 + ethanol, and supercritical CO2 + water + ethanol were measured with a circulation-type apparatus combined with an on-line Fourier transform infrared (FT-IR) spectrometer at 313.2 K and 15.0 MPa. The solubilities of caffeine were determined with the peak absorbances of caffeine at 1190 cm-1. The solubilities of caffeine increase until water is saturated in supercritical CO2. The maximum increase rate is 22%. In CO2 + caffeine + ethanol system, the solubilities of caffeine increase with increasing the concentration of ethanol. The solubility of caffeine becomes five times when 1000 mol m-3 of ethanol is added. In CO2 + caffeine + water + ethanol system, the solubilities of caffeine are smaller than those with single entrainer of water or ethanol. The shape of the peaks of two C{double bond, long}O stretching bands for caffeine were changed by the addition of ethanol. It was confirmed that the interaction species of caffeine interacting with ethanol are produced by deconvolution of the C{double bond, long}O stretching bands. The enhancement of solubility for caffeine in supercritical CO2 by the addition of ethanol is due to the hydrogen bonding between caffeine and ethanol.

Original languageEnglish
Pages (from-to)312-318
Number of pages7
JournalJournal of Supercritical Fluids
Issue number3
Publication statusPublished - Oct 1 2006


All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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