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This paper focuses on the collection of solubility data for pharmaceutical drugs in supercritical carbon dioxide. The experimental techniques used to obtain the data include a supercritical fluid chromatographic technique and a conventional dynamic solubility apparatus. The chromatographic method provided the retention times of the solutes of interest and those of an un-retained substance, which were used to obtain equilibrium partition coefficients. The partition coefficients were subsequently used to obtain solubilities at various temperatures and pressures. The conventional dynamic solubility apparatus was used to provide a calibration parameter for the chromatographic method. The coupling of these two techniques allowed for the fast and accurate determination of the solubility data. Both techniques were validated by measuring the solubility of naphthalene and phenanthrene in carbon dioxide at temperatures between (35 and 55) °C and pressures between (100 and 300) bar. The results agreed within ±10 %, a reasonable experimental uncertainty, to those of other investigators, thus confirming the reliability of the techniques. Additionally, the solubility of anti-inflammatory drugs (naproxen, ibuprofen, and acetaminophen), anti-cancer drugs (paclitaxel, 5-fluorouracil, and thymidine), and anti-HIV drugs (azodicarbonamide and 2-phenyl-4H-1,3-benzoxazin-4-one) were measured in supercritical carbon dioxide for the same range of temperatures and pressures. The results are explained in terms of solute volatility and specific interactions as the most significant factors influencing solubility of pharmaceutical drugs in pure carbon dioxide.

The solubility of nonanoic acid (also known as pelargonic acid) in supercritical carbon dioxide has been determined at (313.15 and 333.15) K over a pressure range of (10 to 30) MPa. The experimental apparatus was of a flow-type, dynamic design, and the solubility was obtained gravimetrically. The solubility ranged from a pelargonic acid concentration of (0.14 ( 0.07) kg • m -3 (333.15 K, 10.0 MPa) to (25.39 ( 0.61) kg • m -3 (313.15 K, 30.0 MPa). The results showed that the solubility of pelargonic acid at 313.15 K was always greater than at 333.15 K at each pressure considered, a common behavior in liquid + SCF phase equilibria. No supercritical fluid solubility data for pelargonic acid were found in the literature. To ensure the validity of the experimental technique, solubility data for oleic acid were measured and compared to literature values. Oleic acid solubilities agreed with literature data within estimated uncertainties. A modified Adachi-Lu model, in terms of dimensionless variables, was used to correlate the solubility of pelargonic acid. Excellent agreement between experimental data and the correlation was found.

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