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A Comparative Study of Chromium(III) Ion-Selective Electrodes Based on N,N-Bis(salicylidene)-o-phenylenediaminatechromium(III)

H.M. Abu-Shawish^a,*, S.M. Saadeh^b, K. Hartani^a and H.M. Dalloul^a

^aChemistry Department, Faculty of Science, Al-Aqsa University, Gaza, Palestine
^bChemistry Department, College of Sciences, The Islamic University of Gaza, P. O. Box 108,Gaza, Palestine

A comparative study was made between three types of Cr(III) ion-selective electrodes: PVC membrane electrode, silver coated electrode and modified carbon paste electrode based on N,N-bis(salicylidene)-o-phenylenediaminatechromium(III) complex (Crsalophen). As anticipated, electrodes with a solid contact, rather than a traditional liquid inner contact, give lower detection limits because of diminished ion fluxes. Often, however, ill-defined solid contact gives rise to instabilities and interferences by oxygen gas. The carbon paste electrode provides a more sensitive and stable device than that afforded by PVC and coated electrodes. The best performance was obtained by an electrode based on the paste containing 3.5 wt% Cr-complex, 48.5% graphite plasticized with a mixture of 24.0 wt% tris(2-ethylhexyl) phosphate (DOPh) + 24.0 wt% dioctyl sebacate (DOS). The sensor has a linear dynamic range of 7.5 × 10^-6 to 1.0 × 10^{-2 M, with a Nernstian slope of 20.1 �± 0.6 mV decade-1}, and a detection limit of 1.8 × 10^-6. It has a short response time of a bout 8 s and is applicable in a pH range of 4.5-7.7. It was successfully used as an indicator electrode in potentiometric titration of Cr(III) with EDTA and in determination of Cr(III) in water samples and chromium in (Crsalophen).

Keywords: Chromium sensor, Potentiometry, Carbon paste electrode, N,N-Bis(salicylidene)-o-phenylenediaminatechromium(III)