Determination of Mn(II) ion by a modified carbon paste electrode based on multi-walled carbon nanotubes (MWCNTs) in different water samples

• Modified carbon paste sensors for the potentiometric response to Mn(II) ions in the wide linear range.
• The electrodes have fast response time and can be used for at least 3 and 4 months without any considerable divergences in the potentials for the modified electrodes.
• The proposed sensors allow selective and stable electrochemical sensing of Mn(II) ions in the presence of large number of alkali, alkaline earth, transition and heavy metal ions.
• The results obtained compared well with those obtained using atomic absorption spectrometry.

For the first time a novel derivatized multi-walled carbon nanotubes-based on Mn(II) carbon paste electrodes is reported. At optimum values of variable conditions, the proposed electrodes responded toward Mn(II) ion linearly in the range of 7.8 × 10−7–1.0 × 10−1 and 2.7 × 10−8–1.0 × 10−1 mol L−1 with slope of 27.72±0.8 and 30.04±0.5 mV decade−1 of Mn(II) ion concentration and detection limit of 7.8 × 10−7 and 2.7 × 10−8 mol L−1 for KTpClPB-CPE (electrode (IV)) and KTpClPB/MWCNTs-CPE (electrode (VIII)), respectively. The electrodes response is independent of pH in the range of 4–8 and 3–9, with a fast response time (8 and 5 s) at 25 °C for electrode (IV) and electrode (VIII), respectively. Moreover, the electrodes also showed high selectivity and long life time (more than 3 and 4 months) for electrode (IV) and electrode (VIII), respectively. The electrodes showed good selectivity for Mn(II) ion toward wide variety of metal ions. The proposed sensors were successfully applied for the determination of Mn(II) ion in different real and environmental samples and as indicator electrodes. The results obtained compared well with those obtained using atomic absorption spectrometry.

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