VOLTAMMETRIC SPECIATION OF BUTYLTIN COMPOUNDS .1. AN ADSORPTIVE CATHODIC STRIPPING METHOD

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 (MET) 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 (3 sigma) were: -0.72 V, 73 mu g L(-1) for TBT; -0.61 V, 78 mu g L(-1) for DBT and -0.49 V, 30 mu g L(-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 (3 sigma) were: -0.61 V, 1.0 mu g L(-1) for DBT and -0.49 V, 2.2 mu g L(-1) for MET. 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 x 10(-4) mol L(-1) tropolone (2-hydroxy-2,4,6-cycloheptatrienone) for 1 min prior to cathodic scanning. Peak potentials and detection limits (30) were: -0.81 V, 4.7 mu g L(-1) for TBT; -0.75 V, 0.52 mu g L(-1) for DBT and -0.65 V, 0.52 mu g L(-1) for MBT.