Voltammetric and impedimetric determinations of selenium(iv) by an innovative gold-free poly(1-aminoanthraquinone)/multiwall carbon nanotube-modified carbon paste electrode

Selenite (Se(4+)), a significant source of water pollution above the permissible limits, is considered a valuable metal by environmentalists. In this study, we described a novel electrochemical sensor that utilized a carbon paste electrode (CPE) that was modified using multiwall carbon nanotubes (MWCNTs) and poly(1-aminoanthraquinone) (p-AAQ) for finding Se(4+) in water samples. Electrochemical quantification of Se(4+) depends on the formation of a selective complex (piaselenol) with p-AAQ. In this work, we prepared a CPE modified by physical embedding of MWCNTs and 1-aminoanthraquione (AAQ), while the polymer film was formed by anodic polymerization of AAQ by applying a constant potential of 0.75 V in 0.1 M HCl for 20 s followed by cyclic voltammetry (CV) from −0.2 to 1.4 V for 20 cycles. The modified CPE was used for differential pulse voltammetry (DPV) of Se(4+) in 0.1 M H(2)SO(4) from 0 to 0.4 V with a characteristic peak at 0.27 V. Further, the proposed sensor was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy (EIS). The analytical conditions regarding the electrode performance and voltammetric measurements were optimized, with the accumulation time and potential, supporting electrolyte, differential-pulse period/time, and amplitude. The EIS results indicated that the p-AAQ/MWCNTs-modified CPE sensor (p-AAQ/MWCNTs/CPE) that also exhibited low charge-transfer resistance (R(ct)) toward the anodic stripping of Se(4+), exhibited good analytical performance toward different concentrations of Se(4+) in a linear range of 5–50 μg L(−1) Se(4+) with a limit of determination (LOD) of 1.5 μg L(−1) (3σ). Furthermore, differential-pulse voltammetry was employed to determine different concentrations of Se(4+) in a linear range of 1–50 μg L(−1) Se(4+), and an LOD value of 0.289 μg L(−1) was obtained. The proposed sensor demonstrated good precision (relative standard deviation = 4.02%) at a Se(4+) concentration of 5 μg L(−1). Moreover, the proposed sensor was applied to analyze Se(4+) in wastewater samples that were spiked with Se, and it achieved good recovery values.