Determination of the temperature dependence of water solubilities of polycyclic aromatic hydrocarbons by a generator column-on-line solid-phase extraction-liquid chromatographic method

An improved dynamic coupled column liquid chromatographic (DCCLC) technique for determining water solubility data of hydrophobic compounds is presented. The technique is based on pumping water through a thermostated generator column in order to generate emulsion-free, saturated aqueous solutions of the compound under study. Through a switching valve system the solute in the aqueous solution is extracted and concentrated by an on-line solid-phase extraction process and subsequently eluted and analyzed by high performance liquid chromatography (fluorescence detection coupled to photodiode array detection). The improvements carried out to the original DCCLC technique have given rise to savings in time for the experimental work and increased sensitivity during the detection and quantification stage. Applicability of the method for studying highly hydrophobic substances is demonstrated by determining water solubility of anthracene and pyrene in the temperature range of 8.9-49.9 and 8.5-32.2 degrees C, respectively. The measured water solubilities are in good agreement with the best available literature data. The method has also been applied to the determination of water solubility of m-terphenyl, 9, 10-dihydrophenanthrene and guaiazulene, in the temperature range of 4.8-49.9, 4.8-25.0, and 4.5-29.9 degrees C, respectively. The uncertainty in the Sw values determined in this work ranged from 0.7% to 4.6%. The experimental water solubility data, as a function of temperature, are fitted to the equation In Sw = A + B/T; where Sw and T are given in mole fraction and Kelvin, respectively.