Ultrasensitive determination of tungsten(VI) on pikomolar level in voltammetric catalytic adsorptive catechol-chlorate(V) system

The renewable mercury film electrode, applied for the determination of tungsten(VI) ultra traces using differential pulse catalytic adsorptive cathodic stripping voltammetry (DPCAdSV) with presence of catechol as a ligand and chlorate(V) is presented. The calibration graph obtained for W(VI) is linear from 0.025 nM (4.5 ng L⁻¹) to 130 nM (23.9 μg L⁻¹) for a preconcentration time of 30 s, with correlation coefficient of 0.9989. For the renewable mercury electrode (Hg(Ag)FE) with a surface area of 4.4 mm² the detection limit for a preconcentration time of 60 s is as low as 0.2 ng L⁻¹. The repeatability of the method at a concentration level of the analyte as low as 0.09 μg L⁻¹, expressed as RSD is 3.1% (n = 5). The proposed method was successfully applied and validated by studying the certified reference material CTA-VTL-2 and simultaneously recovery of W(VI) from spiked water samples.