A new apparatus suitable for accurate measurement of extremely low aqueous solubilities of polynuclear aromatic hydrocarbons (PAH) employing the generator column technique of May et al. has been constructed. In our implementation, the generator column, the extractor column, and the analytical HPLC column are linked by means of a system of three rotary HPLC valves that provide for a complete and convenient control of the measurement sequence including the introduction of calibration samples. The three steps of the measurement, viz. the generation of the saturated solution, the extraction of the solute, and the quantification of the sample are carried out as an in-line procedure, just by switching the valves. The performance of the individual parts and the apparatus as a whole has been optimized and duly validated. The precision of replicate measurements and the day-to-day reproducibility established with anthracene as a test solute are better than +/-2%. The agreement of the measured anthracene aqueous solubilities and derived thermodynamic properties (such as the solution enthalpy) with reliable values previously reported in literature confirms the correct performance of the new apparatus. Using the new apparatus aqueous solubilities of anthracene, 2-methylanthracene, 9-methylanthracene, and 9,10-dimethylanthracene have been measured in 5 K increments in the range of temperatures from 273 to 323 K. The data were fitted to a three parameter smoothing equation with approximately 2% relative standard deviation in the mole fraction solubility. Thanks to the precision and the extent of the measured solubility data, reliable thermodynamic properties (Gibbs energy, enthalpy, and heat capacity) of solution for the four anthracenes in water at infinite dilution could be calculated from these fits. (C) 2003 Elsevier B.V. All rights reserved.