Accumulation and voltammetric determination of complexed metal ions at zeolite-modified sensor electrodes.
Chemically modified electrodes based on zeolite-containing graphite pastes were constructed and evaluated as sensor electrodes for the voltammetric determination of traces of metallic species in solution. Zeolite molecular sieves with pore sizes of 3, 4, 5, and 10 A were all suitable for chemical deposition and subsequent voltammetric quantitation of traces of Cu(II), Cd(II), and Zn(II). The highest sensitivity was obtained using the zeolite with the 10 A pore size. The detection limit obtained for Cu(II) was 0.3 muM following a 2 min chemical deposition. The detection limits for Cd(II) and Zn(II) following a 4 min chemical deposition were 87 nM and 145 nM, respectively. The effects on the zinc signal of coexisting metallic species in the ammonia deposition medium were studied. While the addition of Hg(II) gave rise to increasing zinc signals, the addition of Ag(I), Cu(II), Cd(II), Ni(II), and Co(II) resulted in decreasing zinc signal amplitudes. Most notably, the magnitude of the interference from these latter metal ions correlated well with the coordination numbers of their ammonia complexes. Thus the electrode acted as a device which was sensitive to the size and shape of the interfering metal complex.
Bing
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Kryger
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