Online ligand exchange in the determination of weak acid dissociable cyanide by gas diffusion-flow injection analysis

摘要

A novel ligand exchange method for on-line gas-diffusion flow injection (GD-FI) determination of weak acid dissociable (WAD) cyanide has been successfully developed using a binary ligand combination of 0.10% thiourea and 0.10% pentaethylenehexamine. Complete WAD cyanide recovery with insignificant contribution from the dissociation of stable metal cyanide complexes (non-WAD complexes) has been achieved in the concentration range from 3μg L~(-1) to 10mgL~(-1) cyanide. The proposed GD-FI method offers considerable advantages over the existing standard methods for determining WAD cyanide, as it provides an analysis rate of 60 samples h~(-1) with a satisfactory reproducibility (average RSD=1.0% at n=3) and can be fully automated. A very good agreement between the proposed method and the standard distillation method has been observed when both methods have been applied to the determination of WAD cyanide in samples from the gold mining industry.