Aqueous solubilities of non-ortho and mono-ortho PCBs at four temperatures

The temperature-dependent aqueous solubilities of 12 non-ortho and mono-ortho coplanar PCBs (IUPAC Nos. 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, and 189) were determined at 5°C, 15°C, 25°C, and 35°C. A generator-column/extractor-column technique was used, followed by off-line GC/ECD analysis. The relative standard deviations for the measurements were 7.4%. The determined solubilities increase exponentially with temperature from 5°C to 35°C for all 12 tested PCBs, and their enthalpies of solution were determined to range from 22.3 to 45.0 kJ/mol. The determined solubilities of PCB 77 at 25°C were further compared with the results reported previously and with the calculated data. Within homolog groups, congeners with more ortho-substitution generally have greater aqueous solubilities. The measured aqueous solubilities of 58 congeners compiled from the literature and from this study were used for evaluation of quantitative structure-property relationships relating chlorine substitution pattern to the aqueous solubilities. A useful equation by which to estimate aqueous solubilities was derived on the basis of multi-regression analysis, which employs easily calculable molecular descriptors. The validity of this equation is demonstrated by comparison of the estimated values with experimental values. This newly developed model agrees well with log Kow-based model predictions.