Development of methodology for the visual identification of Tributyltin (TBT) in antifouling paint matrices

Organotin compounds (OTC), mainly tributyltin (TBT), have been used since the 1970s as biocides in the composition of antifouling paints. Due to its physical-chemical characteristics, TBT has high toxicity to the marine environment affecting non-target organisms. The present study aims to develop a method of direct visual identification of TBT in antifouling paints using the cyclopalladate complex, 4- (2-thiazolylazo) resorcinol (TAR-Pd), synthesized in our laboratory. Tests were performed in blank and in the paint matrix with the following OTC: TBT-O; TBT-Cl; TPT-Cl; DBT-Cl (tributyltin oxide, tributyltin chloride, triphenyltin chloride, dibutyltin chloride), in addition to the SnCl₄ and SnCl₂ compounds (tin IV chloride and tin II chloride), all at a concentration of approximately 20 g/ kg of dry paint). The test was performed by applying paint samples to test bodies and scraping a few tens of milligrams of the dry paint film. The scraped paint samples were submitted to the test, showing a different staining reaction for the TBT-Cl and SnCl₄ samples concerning blank and other samples (TBT-O, TPT, DBT-Cl, and SnCl₂). Solution tests were performed to characterize reaction products by spectroscopy in the visible band. The method developed has potential for application in real samples, being selective for TBT-Cl and SnCl₄ in an acid medium, obtaining a limit of detection, in the range of 1-10 mg/kg dry paint.