Hexafluorotantalate(V)-Selective Coated Graphite Electrode based on Malachite Green
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Date
1996-06
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Addis Ababa Universty
Abstract
An attempt was made to develop hexafluorotantalate(V)-selective coated graphite
electrodes based on Malachite Green, Crystal Violet, and Ethyl Violet using fchloronaphthalene,
tri-n-bUI)'1 phosphate, and dimethylphthalate as plasticizers. The
electrode prepared by coating Malachite Green-hexaflllorotantalate(V) extract in fchloronaphthalene
\Vith a PVC matrix on a graphite rod \Vas found to give a Nernstian
response and hence was studied in detail. Potential measurements with the coated graphite
electrode were made against a plastic sleeve HF-resistant Ag/AgCI external reference
electrode. Optimum response of the electrode was observed in test solutions made 1 mollL
in both sulphuric and hydrofluoric acids. The response characteristics of the electrode
were evaluated. The linear range, slope, and detection limit were found to be f.O x f 0.5
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1.0 X 10.2 mollL tantalum(V), 58.0 ± 1.5 mV/decade, and 3.98 x 1rJ mollL tantalllm(V),
respectively. The precision of the method developed \Vith the electrode \Vas estimated to be
2% and the electrode functioned properly for three months. The effects of diverse ions on
the electrode response to hexafluorotantalate(V) were studied, and the potentiometric
selectivity coefficients lVere evaluated. The electrode was found to be highly selective to
hexafluorotantalate(V). It was found that the response of the electrode to
hexafluorotantalate is free from inteiference of niobium which commonly occurs with
tantalum. The analytical application of the electrode to the detennination of tantailim in
synthetic matrices and real ore samples was also studied. The results obtained using four
potentiometric techniques are in good agreement \Vith the actllal or certified values.
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Keywords
Hexafluorotantalate(V)-selective coated graphite electrodes