Differential pulse cathodic stripping voltammetric determination of manganese(II) and manganese(VII) at the 1‐(2‐pyridylazo)‐2‐naphthol‐modified carbon paste electrode

Electroanalysis - Tập 9 Số 1 - Trang 45-51 - 1997
Soo Beng Khoo1, Ming Koon Soh1, Qiantao Cai1, Miriam Rehana Khan1, Si‐Xuan Guo1
1Department of Chemistry, National University of Singapore, Kent Ridge, Singapore 0511

Tóm tắt

AbstractA 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 200s 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) (150s accumulation), Co(II), Hg(II) and Fe(II) at 1.00 × 10−5M 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.

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Electroanalysis

Tập 9 Số 1

45-51

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