A novel ion selective membrane potentiometric sensor for direct determination of Fe(III) in the presence of Fe(II).

A new PVC membrane potentiometric sensor that is highly selective to Fe(III) ions was prepared by using 2-[(2-hydroxy-1-propenyl-buta-1,3-dienylimino)-methyl]-4-p-tolylazo-phenol [HPDTP] as a suitable carrier. The electrode exhibits a linear response for iron(III) ions over a wide concentration range (3.5 x 10(-6) to 4.0 x 10(-2)) with a super Nernstian slope of 28.5 (+/-0.5) per decade. The electrode can be used in the pH range from 4.5 to 6.5. The proposed sensor shows fairly a good discriminating ability towards Fe(3+) ion in comparison to some hard and soft metals such as Fe(2+), Cd(2+), Cu(2+), Al(3+) and Ca(2+). It has a response time of <15s and can be used for at least 2 months without any measurable divergence in response characteristics. The electrode was used in the direct determination of Fe(3+) in aqueous samples and as an indicator electrode in potentiometric titration of Fe(III) ions.