Direct determination of the organic extent of tin species in environmental samples by X-ray absorption near-edge structure (XANES)

Introduction Organotin compounds have been used since the 1960s as an effective antifouling agent in paints applied to ships and aquaculture nets in the marine environment. However, organotin compounds cause damage to nontarget marine organisms by leaching from the coating applied to boat hulls into the marine environment. For Sn analyses, speciation of the organotin compounds has been of great interest due to their species-dependent toxicity. Generally, trisubstituted (R3SnX) organotins (R = butyl or phenyl) are more toxic than diand mono-substituted organotin compounds, and the anion (X) has little influence on the toxicity. In recent years, chromatographic techniques such as gas chromatography (GC) or liquid chromatography (LC), coupled with appropriate detectors such as FPD (flame photometric detector), MS (mass spectrometer), and ICP-MS (inductively coupled plasma mass spectrometer) have been widely used for the analysis of organotin compounds. These analytical methods need many complicated pretreatment procedures, such as extraction, enrichment, and derivatization, which may cause some errors due to alteration of Sn species and poor recovery in the analyses. In this study, we have established a method for determining Sn speciation using synchrotron-based X-ray absorption fine structure (XAFS) as a non-destructive method to identify organotin compounds in solid environmental samples such as marine sediments, biological samples, and antifouling paints.