Solubilities of Some 9-Anthrone Derivatives in Supercritical Carbon Dioxide Ali Reza Karami, † Yadollah Yamini, † Ali Reza Ghiasvand, † Hashem Sharghi, ‡ and Mojtaba Shamsipur* ,§ Departments of Chemistry, Tarbiat Modarres University, Tehran, Iran; Shiraz University, Shiraz, Iran; and Razi University, Kermanshah, Iran The equilibrium solubilities of five recently synthesized anthrones have been measured in supercritical carbon dioxide using a simple and reliable static method. The measurements were performed in the pressure range (101-355) bar at the temperatures (308, 318, 328, 338, and 348) K. The measured solubilities were correlated using a semiempirical model. The calculated results show satisfactory agreement with the experimental data. Introduction Supercritical fluid extraction (SFE) is becoming an important tool in analytical science and has been rapidly developed in the past few years. 1 SFE acts as a direct alternative to conventional liquid-solid extraction tech- niques. The main advantages of SFE over conventional methods include shorter extraction times, reduced solvent use, and the potential for selective analyte extraction by varying the pressure, temperature, or modifier. 2 In the past decades, widespread attention has been paid to the supercritical fluids, due to their potential application in extraction processes in food processing, pharmaceutical, and petroleum industries as well as in the synthesis of organic molecules. 3-6 Information on solubilities in super- critical fluids is of vital importance in order to efficiently design extraction procedures based on supercritical flu- ids. 7,8 9,10-Anthraquinones and 9-anthrones are the largest group of natural quinones and historically the most im- portant. 9 Besides a wide variety of chemical and industrial applications, 9-11 recently the synthetic derivatives of an- thraquinone and anthrone, as well as their naturally occurring derivatives, have been used for medical pur- poses. 10 We have recently reported the solubilities of some dihydroxy-9,10-anthraquinone derivatives 12,13 and hydroxy- xanthene derivatives 14 in supercritical carbon dioxide. This work was undertaken to determine the solubilities of 1-hydroxy-2-methyl-9-anthrone (A1), 1-hydroxy-2,4-di- methyl-9-anthrone (A2), 1-hydroxy-2-ethyl-9-anthrone (A3), 1,8-dihydroxy-9-anthrone (A4), and 1,8-dihydroxy-2-(prop- 2′-enyl)-9-anthrone (A5) in supercritical carbon dioxide over a wide range of temperatures and pressures. The measured solubilities were nicely correlated using a semiempirical model proposed by Bartle et al. 7 Experimental Section HPLC-grade methanol (Merck) was used as received. Pure carbon dioxide (Sabalan, Tehran, 99.99%) was used for all extractions. The anthrone derivatives A1-A5 were synthesized and purified as described before. 15 The purities of anthrone derivatives were confirmed by spectroscopic data and elemental analysis. The structures of the an- throne derivatives used are shown in Figure 1. A Suprex MPS/225 integrated SFE/SFC system equipped with a modified static system for the solubility determi- nation in the SFE was used. A detailed description of the apparatus and operating procedure is given elsewhere. 12,13 The solubility measurements were based on the assump- tion that the mixture properties of pure supercritical fluid CO 2 are identical. Solubility measurements were accom- plished with a 1-mL extraction vessel in the pressure range from (101 to 355) bar at the temperatures (308, 318, 328, 338, and 348) K for a duration of 30 min. It should be noted that, by monitoring the solubility data versus time, 30 min was found to be adequate to ensure the attainment of equilibrium. The solid solutes (100 mg) were mixed well with glass beads and packed into the extraction vessel. This procedure increases the contact surface between the sample and the supercritical fluid and, consequently, reduces the * To whom correspondence should be addressed. E-mail: mshamsipur@ yahoo.com. † Tarbiat Modarres University. ‡ Shiraz University. § Razi University. Figure 1. Structures of anthrone derivatives. 1371 J. Chem. Eng. Data 2001, 46, 1371-1374 10.1021/je0101045 CCC: $20.00 © 2001 American Chemical Society Published on Web 09/06/2001