Analytical Sciences

Novel Potentiometric Membrane Sensor for the Determination of Trace Amounts of Chromium(III) Ions

Mohammad Reza GANJALI,*  Farhang MIZANI,* Masoud SALAVATI-NIASARI,** and Mehran JAVANBAKHT***

*Department of Chemistry, Faculty of Science, Tehran University, Tehran, Iran
**Department of Chemistry, Faculty of Science, Kashan University, Kashan, Iran
***Department of Chemistry, Faculty of Science, Tarbiat Modarres University, Tehran, Iran

A plasticized Cr³⁺ ion sensor by incorporating 2,3,8,9-tetraphenyl-1,4,7,10-tetraazacyclododeca-1,3,7,9-tetraene (TTCT) ionophore exhibits a good potentiometric response for Cr³⁺ over a wide concentration range (1.0 x 10^-6 - 1.0 x 10^-1 M) with a slope of 19.5 mV per decade. The sensor response is stable for at least three months. Good selectivity for Cr³⁺ in comparison with alkali, alkaline earth, transition and heavy metal ions, and minimal interference are caused by Li⁺, Na⁺, K⁺, Co²⁺, Hg²⁺, Ca²⁺, Pb²⁺ and Zn²⁺ ions, which are known to interfere with other chromium membrane sensors. The TTCT-based electrode shows a fast response time (15 s), and can be used in aqueous solutions of pH 3 - 5.5. The proposed sensor was used for the potentiometric titration of Cr³⁺ with EDTA and for a direct potentiometric determination of Cr³⁺ content in environmental samples.

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