Voltammetric speciation of butyltin compounds

Abstract

A new differential pulse adsorptive cathodic stripping voltammetric (AdSV) method for the determination of butyltin species at the ultra-trace level is compared with two other voltammetric methods: differential pulse polarography (DPP) and differential pulse anodic stripping voltammetry (ASV). Tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) chlorides can be determined simultaneously by DPP in 20% (v/v) methanol-water solution, 0.05 mol L−1 in tetraethylammonium perchlorate (TEAP) at pH 2.5. Peak potentials and detection limits (3σ) were: −0.72 V, 73 μg L−1 for TBT; −0.61 V, 78 μg L−1 for DBT and −0.49 V, 30 μgL−1 for MBT. Using ASV, DBT and MBT can be determined after preconcentration at −0.70 V. In 20% (v/v) methanol-water solution, 0.05 mol L−1 in TEAP at pH 2.5 the ASV peak potentials and detection limits (3σ) were: −0.61 V, 1.0 μg L−1 for DBT and −0.49 V, 2.2 μg L−1 for MBT. Using the new method, the butyltin species were adsorptively accumulated on the hanging mercury drop electrode as the tropolone complexes from 20% (v/v) methanol-water acetate buffer (0.08 mol L−1, pH 4.5) solution containing 1.5×10−4 mol L−1 tropolone (2-hydroxy-2,4,6-cycloheptatrienone) for 1 min prior to cathodic scanning. Peak potentials and detection limits (3σ) were: −0.81 V, 4.7 μg L−1 for TBT; −0.75 V, 0.52 μg L−1 for DBT and −0.65 V, 0.52 μg L−1 for MBT.