Aqueous Speciation and 1-Octanol−Water Partitioning of Tributyl- and Triphenyltin:  Effect of pH and Ion Composition

Abstract

Due to their widespread use as antifouling agents in boat paints, tributyltin (TBT), and triphenyltin (TPT) have been found to be present in marine and freshwater ecosystems at concentrations exceeding acute and chronic toxicity levels. In order to assess the environmental behavior and particularly the bioavailability and bioaccumulation of these compounds, their aqueous speciation and partitioning behavior between nonaqueous phases and water need to be known. In this work, the effect of pH and of the concentration of various anions on the 1-octanol-water partitioning of TBT and TPT has been systematically investigated. A simple model is presented that enables a quantitative description of the overall 1-octanol-water distribution ratio of TBT and TPT as a function of pH and salt concentration. Acidity constants of 6.25 and 5.20 were determined for TBT and TPT, respectively. Furthermore, the aqueous phase complex formation constants with chloride, perchlorate, bromide, and nitrate as well as the 1-octanol-water partition constants of the corresponding complexes are reported. In addition, the Setschenov constants of TBT-and TPT-hydroxide have been determined for NaCl (0.6 and 0.4, respectively) and are estimated for other salts.

Distribution of butyltins in waters and sediments of the Mandovi and Zuari estuaries, west coast of India

“…TBT exhibits both lipophilic and ionic properties (Arnold et al 1997;Blanca 2008). This means TBT levels will be influenced by the concentrations of total lipids and organic carbon.…”

Harmful Elements in Estuarine and Coastal Systems

“…Tributyltin and triphenyltin are ionizable and make complexes by reacting with different ligands present in the environment (Arnold et al 1997;Buck et al 2003). The fate and accumulation of the organotion compounds are determined by the speciation of organotin compounds.…”

“…Speciation is normally regulated by the pH and salinity of the water. In seawater the hydroxyl-complexes (>93 %) are the dominant species, whereas under acidic medium (pH 6), the TBT-cation exists in addition to the neutral TBT-Cl and TBT-OH complexes (Arnold et al 1997;Burton et al 2005) …”

Comparative Study of Tributyltin Adsorption onto Mesoporous Silica Functionalized with Calix[4]arene, p-tert-Butylcalix[4]arene and p-Sulfonatocalix[4]arene

“…The adsorption behaviour can be explained through the TBT species and the functional group existing in the surface of the adsorbent. TBT is characterized as a weak acid having a pKa of 6.3 [38] comprising of cationic form (TBT + , (C 4 H 9 ) 3 Sn ) in equilibrium with a neutral form (TBTOH, (C 4 H 9 ) 3 SnOH) as evident from Equation (1):…”