Electrochemical speciation of organotin compounds in water and sediments. Application to sea water after ion-exchange separation

For the quantitative speciation of tributyltin, Bu₃Sn⁺ (TBT), in the presence of dibutyltin, Bu₂Sn²⁺ (DBT), monobutyltin, BuSn³⁺ (MBT), triphenyltin, Ph₃Sn⁺ (TPT), and inorganic tin in water samples and sediments, an accurate, reproducible, simple and rapid electrochemical method was developed. After extraction of the organotin compounds with dichloromethane, TBT could be selectively determined as species by alternating current polarography directly in the organic phase without any derivatisation. The successful application of this technique could be proved by the results obtained by intercomparison exercises on TBT in water samples and sediments, organized by the Community Bureau of Reference (BCR). For the application of this technique to sea water samples a preliminary ion exchange separation of TBT from the major components of sea water was performed, achieving a detection limit for TBT in the ppt range.