Analytical Sciences

Novel Membrane Potentiometric SulfateIon Sensor Based on Zinc-Phthalocyanine for the Quick Determination ofTrace Amounts of Sulfate

Mohammad RezaGANJALI,*¹  Mohammad RezaPOURJAVID,*¹ Mojtaba SHAMSIPUR,*²Taherh POURSAERI,*³ Morteza REZAPOUR,*¹Mehran JAVANBAKHT,*³ and HashemSHARGHI*⁴

*1 Department of Chemistry, TehranUniversity, Tehran, Iran
*2 Department of Chemistry, Razi University,Kermanshah, Iran
*3 Department of Chemistry, Tarbiat ModarresUniversity, Tehran, Iran
*4 Department of Chemistry, Shiraz University,Shiraz, Iran

Poly(vinyl chloride) (PVC) based membranesof zinc-phthalocyanine (ZPC) with hexadecyltrimethylammonium bromide (HTAB)as a cation excluder, and dibutyl phthalate (DBP) and benzyl acetate (BA)as plasticizing solvent mediators were prepared and investigated as aSO₄^2- selective electrode. The best performance wasobserved with a membrane having a composition of ZPC-PVC-HTAB-BA in a ratioof 5%:32%:3%:60%, which works well over a wide concentration range (1.0 x10^-2 - 1.0 x 10^-6 M) with a Nernstian slope of -29.2mV per decade of activity, between the pH values of 2.0 to 7.0. Thissensor shows a very fast response time of 10 s, and can be used over aperiod of 2 months with good reproducibility. The proposed sensor displaysexcellent selectivity for SO₄^2- over a large numberof common inorganic anions. The sensor has been successfully applied forthe direct and indirect determination of sulfate and zinc in zinc sulfatetablets, respectively. It was also used as an indicator electrode in thepotentiometric titration of sulfate ions with barium ions.

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