Cyanide selective electrodes based on a porphyrinatoiron(III) chloride derivative

Tetrakis-4-chlorophenylporpherinatoiron(III) chloride (FeT(4-ClP)PCl) was used as an ionophore for the construction of two kinds of cyanide ion selective electrodes, i.e., Polyvinilchloride (PVC) membrane and membrane coated graphite electrodes. Different membrane constituents were optimized for the electrodes. Membranes with 65.5% o-nitrophenyl octyl ether (o-NPOE), 32.7% PVC, 0.8% ionophore, and 1.0 cetyltetramethylammonium bromide (CTAB) gave the best Nernstian responses to cyanide ion activity in the concentration range of 6.3 × 10−7–1.2 × 10−2 M. A polyaniline thin film was coated over the graphite electrodes prior to membrane coating; this modification was found suitable for both smooth functioning and fast response time of the graphite electrodes. Response time of the electrodes was found to be about 5 s. Finally, a broader concentration range was found for coated graphite electrodes with respect to the PVC membrane electrodes.