Journal of Chromatography A, 1140 (2007) 195–204 Aqueous solubility data for pressurized hot water extraction for solid heterocyclic analogs of anthracene, phenanthrene and fluorene Pavel Kar´ asek, Josef Planeta, Michal Roth ∗ Institute of Analytical Chemistry, Academy of Sciences of the Czech Republic, Veveˇ r´ ı 97, 60200 Brno, Czech Republic Received 27 September 2006; received in revised form 16 November 2006; accepted 17 November 2006 Available online 1 December 2006 Abstract We report the aqueous solubilities of phenanthrene and several solid three-ring aromatic heterocycles (phenanthridine, acridine, phenazine, thianthrene, phenothiazine, phenoxathiin, phenoxazine, carbazole, dibenzofuran, dibenzothiophene, and 4,6-dimethyldibenzothiophene) at tem- peratures ranging from 313 K to the solute melting point and at a pressure of 5 MPa. The data were measured by dynamic saturation method using an in-house-assembled apparatus for pressurized hot water extraction (PHWE). The solute from a known mass of the saturated aqueous solution was transferred to an organic solvent (hexane or toluene), and the organic phase was analyzed by GC/MS. In any of the solutes, the GC/MS records did not indicate any noticeable decomposition within the temperature range of the measurements. The resultant solubilities were converted to activity coefficients of the individual solutes in saturated aqueous solutions, and the results are discussed in terms of temperature and type/number of heteroatoms. © 2006 Elsevier B.V. All rights reserved. Keywords: Pressurized hot water; Solubility; Aromatic heterocycle; Extraction; Sample preparation; Activity coefficient 1. Introduction The needs for sustainable development and for environ- mentally benign processes result in growing use of tunable green solvents [1], with water providing the greenest alternative available. Here, “tunability” means the possibility to achieve significant variations in solvent power and properties through changes in the operating temperature and pressure. The prop- erties that control the solvating abilities of water, i.e., the static relative permittivity (dielectric constant), the cohesive energy density, and the ion product, vary widely with temperature and pressure [2–4]. Consequently, water is not only the greenest but also the most tunable solvent [5]. Liquid water at temperatures between the normal boiling point and the critical point, often referred to as pressurized hot water (PHW) [6], can even be used as a benign alterna- tive solvent for organic reactions [7,8]. Since its first reported use as a solvent in analytical extractions [9], PHW has seen many interesting applications in sample treatment procedures ∗ Corresponding author. Tel.: +420 532 290 171; fax: +420 541 212 113. E-mail address: roth@iach.cz (M. Roth). for analytical chemistry [10–12], extractions of plant materials [13–16], environmental remediation processes [17–19], decom- position of non-biodegradable polymers [20], or hydrothermal degradation of silk protein to amino acids [21]. The reactions in PHW are a complement to the reactions conducted under more drastic conditions in supercritical water [22–26]. In spite of the frequent applications of pressurized hot water extraction (PHWE) as a sample treatment method, the underly- ing fundamental data available to date seem far from being of satisfactory amount and diversity. Most previous measurements of solubilities of heavy organic solids in PHW were focused on polycyclic aromatic hydrocarbons (PAHs) [27–32], and a pre- dictive correlation with pure component properties has recently been developed [33] to estimate PAH solubilities in PHW as functions of temperature and pressure. Solubility data for other classes of important organic solid solutes, however, are scarce [28–30]. Therefore, to strengthen the rational background for PHWE process design and to improve understanding of the solvent properties of PHW, extension of the solubility mea- surements in PHW to other classes of heavy organic solutes is necessary. Given the data base already available for PAHs, nitrogen- and sulfur-containing aromatic heterocycles are natu- ral candidates in this respect, both because of their importance 0021-9673/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2006.11.061