AQUEOUS SPECIATION AND 1-OCTANOL-WATER PARTITIONING OF TRIBUTYL-TIN AND TRIPHENYLTIN - EFFECT OF PH AND ION COMPOSITION

Due to their widespread use as antifouling agents in boat paints, trib utyltin (TBT), and triphenyltin (TPT) have been found to be present in marine and freshwater ecosystems at concentrations exceeding acute an d chronic toxicity levels. In order to assess the environmental behavi or and particularly the bioavailability and bioaccumulation of these c ompounds, their aqueous speciation and partitioning behavior between n onaqueous phases and water need to be known. In this work, the effect of pH and of the concentration of various anions on the l-octanol-wate r partitioning of TBT and TPT has been systematically investigated. A simple model is presented that enables a quantitative description of t he overall I-octanol-water distribution ratio of TBT and TPT as a func tion of pH and salt concentration. Acidity constants of 6.25 and 5.20 were determined for TBT a nd TPT, respectively. Furthermore, the aqueo us phase complex formation constants with chloride, perchlorate, bromi de, and nitrate as well as the 1-octanol-water partition constants of the corresponding complexes are reported. In addition,the Setschenov c onstants of TBT-and TPT-hydroxide have been determined for NaCl (0.6 a nd 0.4, respectively) and are estimated for other salts.