Measurement and modeling of solubilities of capsaicin in high-pressure CO2

Measurements on solid–fluid equilibrium were performed for capsaicin in sub- and supercritical carbon dioxide (CO2) at several temperatures (298, 308, 313 and 318 K) and over a pressure range from 6 to 40 MPa, to verify the operation of a new static–analytic set-up. This set-up consisted of a high-pressure static equilibrium cell coupled to a high-performance liquid chromatograph (HPLC). The new equilibrium data have been critically compared with available literature data; some differences were observed, especially at the two highest assayed temperatures. Experimental solubility values were correlated by using three different models, a density-based model, a cubic equation of state with quadratic mixing rules, and a group contribution equation of state. The density correlation results showed good agreement with the experimental data, in contrast to the results of both equations of state.