Organotin speciation in aquatic matrices by CGC/FPD, ECD and MS, and LC/MS

Summary

The sensitivity and reproducibility of CGC coupled to selective detectors for the determination of alkyl and aryltin compounds (R_xSnY_z, where R=C₄H₉ or C₆H₅, and Y=CH₃ or Cl) (x+z=4) have been evaluated. In this regard, single or dual flame FPD configurations, with or without interference filter (600 nm) have been compared. The electron impact (EI) selected ion monitoring detection (SIM) CGC-MS was also considered for confirmation of the FPD assignments as well as for quantitative purposes. Alternatively, the accuracy and sensitivity of the direct analysis of organotin chlorides (Y=Cl) by cold on-column injection CGC-ECD or by thermospray LC-MS were determined. According to this, an analytical protocol based on acid digestion, extraction with organic solvents modified with tropolone, derivatization with CH₃MgCl, cleanup with alumina and CGC-FPD analysis has been successfully applied to the characterization of organotin compounds in seawater, sediments and biota. The relative detection limits of the whole procedure were dependent of the tin species and the environmental compartment considered, ranging from 0.5 to 6.5 ng l⁻¹ for seawater, in the filterless operation mode, and 0.1–2 ng g⁻¹ and 0.7–8 ng g⁻¹ for sediments and biota, respectively, using a 600 nm interference filter. Reproducibility was in the range of 15% RSD. Aryl and hydroxyalkyltin were identified for the first time in the aquatic compartments.