Multi-walled carbon nanotube and nanosilica chemically modified carbon paste electrodes for the determination of mercury(ii) in polluted water samples

Abstract

Novel carbon paste ion selective electrodes based on the 1,4-bis(6-bromohexyloxy)benzene (BHOB) ionophore were constructed in order to determine the Hg(II) ion concentration. Multi-walled carbon nanotubes (MWCNTs) and nanosilica modifiers were used for improving the response characteristics of mercury carbon paste sensors. MWCNTs have good conductivity which helps the transduction of the signal in carbon paste electrodes. These potentiometric sensors respond to Hg(II) ions in wide linear concentration ranges of 1 × 10⁻¹ to 1.0 × 10⁻⁷ and 1.0 × 10⁻¹ to 1.8 × 10⁻⁸ mol L⁻¹ with Nernstian slopes of 28.75 ± 0.46 and 29.92 ± 0.15 mV decade⁻¹ of Hg(II) ions and detection limits of 1 × 10⁻⁷ and 1.8 × 10⁻⁸ mol L⁻¹ for the MWCNT-CPE (electrode V) and MWCNT/nanosilica-CPE (electrode VII), respectively. The electrodes were pH independent within the ranges of 3.0–7.5 and 2.5–8.5, with a fast response time of about 7 and 4 s, and can be used for at least 110 and 145 days without any considerable divergence in the potentials of electrode (V) and electrode (VII), respectively. The proposed sensors thus allowed a sensitive, selective, simple, low-cost, and stable electrochemical response to Hg(II) ions in the presence of a large number of alkali, alkaline earth, transition and heavy metal ions. Such abilities promote new opportunities for determining Hg(II) ions in a wide range of real samples. The results obtained were compared with those obtained using inductively coupled plasma atomic emission spectrometry (ICP-AES).