Analytical Sciences

Abstract − Analytical Sciences, 19(2), 235 (2003).

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.