Differential Pulse Cathodic Stripping Voltammetric Determination of Manganese(II) and Manganese(VII) at the 1-(2-Pyridylazo)-2-Naphthol-Modified Carbon Paste Electrode

Soo Beng Khoo, Ming Koon Soh, Qiantao Cai, Miriam R. Khan, Si Xuan Guo

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Abstract

A carbon paste electrode modified with 1-(2-pyridylazo)-2-naphthol was fabricated and used to preferentially accumulate Mn(II) at open circuit. After medium exchange, the accumulated Mn(II) at the electrode surface was electrochemically oxidized. The hydrated MnO2 thus formed was then cathodically stripped using differential pulse voltammetry. Various factors influencing the accumulation and stripping were studied. An optimized procedure was then developed for the determination of Mn(II). Mn(VII) could also be determined by chemical conversion to Mn(II) using acidified H2O2. Following this, the Mn(VII) concentration could be obtained by subtraction. Under optimum conditions, a detection limit of 6.9 × 10-9 M Mn(II) (0.38 ppb) was found for 200 s accumulation. For 8 determinations, each of Mn(II) concentrations of 1.00 × 10-6 M, 1.00 × 10-7 M and 1.00 × 10-8 M, relative standard deviations of 2.90 %, 4.46 % and 7.20 % were obtained, respectively. Selected metal ions were tested for interferences and it was found that, when determining 1.00 × 10-6 M Mn(II) (150 s accumulation), Co(II), Hg(II) and Fe(II) at 1.00 × 10-5 M interfered. These interferences were readily eliminated by masking with complexing agents such as sodium citrate and sodium diethyldithiocarbamate. The developed method was tested using a certified sample and then applied to the determination of manganese in seawater.

Original languageEnglish
Pages (from-to)45-51
Number of pages7
JournalElectroanalysis
Volume9
Issue number1
DOIs
Publication statusPublished - Jan 1997
Externally publishedYes

Keywords

  • 1-(2- Pyridylazo)-2-Naphthol
  • Manganese
  • Modified electrodes
  • Stripping voltammetry

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