A voltammetric approach to the quantification of tungsten in environmental waters using a solid bismuth microelectrode

Abstract

In this paper, a novel eco-friendly solid bismuth microelectrode for direct tungsten quantification by cathodic stripping voltammetry (CSV) is discussed. The novelty of the proposed sensor results from the fact that the used microelectrode (Ø = 25 µm) exhibits perfect long-term persistence. Moreover, on account of spherical diffusion and insensitivity to the presence of oxygen in the solution the analysis could be performed at the point of sampling. The instrumental and chemical factors influencing the sensitivity of the sensor were thoroughly investigated and their most favorable values were selected (pH = 2.88, acetic acid concentration: 0.1 M; activation potential/time: −1.8 V/1 s; accumulation potential/time: −0.5 V/20 s). Under selected conditions, the method exhibits linearity in the range of 1 × 10−8 to 5 × 10−6 M, while the detection boundary was calculated to be 1.3 × 10−9 M. This method has been shown to be highly selective and insensitive to the presence of even 10 mg L−1 of humic substances due to the addition of the adsorptive Amberlite XAD-7 resin to the test solution. In keeping with the outlined procedure, the certified reference materials (SPS-SW1, SPS-WW1, NAAS-5), tap and well water samples were analyzed without any pretreatment and recovery values from 90.4 to 108.5% were obtained.