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Response of copper(II) ion-selective electrodes in seawater
Journal article   Peer reviewed

Response of copper(II) ion-selective electrodes in seawater

Roland De Marco
Analytical Chemistry, Vol.66(19), pp.3202-3207
1994
DOI: https://doi.org/10.1021/ac00091a033
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https://doi.org/10.1021/ac00091a033View
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Abstract

A comparison of the behavior of three types of Cu(II) ionselective electrode (i.e., copper sulfide, copper selenide, and copper/silver sulfide) in seawater has been undertaken. X-ray photoelectron spectroscopy and X-ray diffraction have shown that the unacceptably high detection limit of the CuS electrode (∼ 10-4 M Cu2+) is due to membrane oxidation to CuS04 and Cu3(SO4)(OH)4. Bare Cu1.8Se and CuS/Ag2S electrodes displayed Nernstian response (i.e., ∼ 100% Nernstian slope) in the range 10-1610-8 M free Cu(II) with Cu(II)-ethylenediamine buffers also containing 0.6 M NaCl. It is proposed that amelioration of the chloride interference at low levels of free Cu(II) (i.e., <10-8 M) is due to kinetic limitations of the membrane reaction that is responsible for the chloride interference. Corrosion of the Cu1.8Se electrode contaminated seawater with a high level of Cu(II) (∼ 100 nM), while the CuS/Ag2S electrode released a much lower amount of Cu(II) (∼ 2.4 nM). Electrode carryover and contamination of seawater by adsorbed free Cu(II) is minimized by equilibration of the electrode in a sacrificial Cu(II) buffer (i.e., pCufree = 15) before analysis. The behavior of Cu(II) electrodes in seawater has been interpreted in relation to free Cu(II) levels, and results indicate a proportionality between free Cu(II) and the electrode potential.

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