Electrochemical sensing of copper employing tellurium film electrode

An ASV procedure featuring a new tellurium film electrode deposited in-situ on a glassy carbon substrate in 0.1 M HCl is presented. The electrochemical behavior of the tellurium film electrode with regard to its applicability in the ASV determination of copper(II) was thoroughly studied and discussed. It was found that during the accumulation step in 0.1 M HCl, Cu(II) is co-deposited with tellurium at − 0.5 V in the form of a Cu-Te alloy. When SW-ASV is used, Cu(II) accumulated in-situ with Te(IV) on the GC electrode yields a stripping peak at a potential ca. 240 mV more positive than that obtained at a bare GC; this peak is also 3.65 times higher. The key parameter that determines the performance of the TeF/GC electrode in the ASV determination of Cu(II) is the concentration of Te(IV) present in the supporting electrolyte. For higher concentrations of Cu(II) in the range from 25 to 125 μg L−1 and a time of accumulation equal to 60 s, the Te(IV) concentration of 150 μg L−1 is recommended. In the Cu(II) concentration range from 0.5 to 25 μg L−1 and a longer accumulation time of 300 s, 50 μg L−1 of Te(IV) is optimal. These conditions allow a relatively positive potential window to be applied and, consequently, make the TeF/GC electrode a viable alternative to the BiFE and SbFE in the determination of Cu(II) traces via anodic stripping voltammetry. The application of the tellurium film electrode under the optimized conditions (supporting electrolyte containing 0.1 M HCl and 50 μg L−1 Te(IV), 300 s of accumulation at −0.5 V, square wave voltammetric mode) assures a sensitive stripping voltammetric response for Cu within the concentration range of 0.5 to 25 μg L−1, good precision (RSD = 4%), and a low detection limit (0.18 μg L−1 Cu). Possible interferences from the co-existing ions and surface-active substance were investigated. The proposed method of copper determination was successfully applied and validated with the use of mineral water sample.