Highly Selective PVC‐Membrane Electrodes Based on Three Derivatives of (Tetraphenylporphyrinato)Cobalt(III) Acetate for Determination of Trace Amounts of Nitrite Ion

Three different para ‐substituted derivatives of (tetraphenylporphyrinato) cobalt(III) acetate were examined as suitable ionophores for the preparation of polymeric membrane (PME) and coated graphite (CGE) nitrite‐selective electrodes. The electrodes revealed a Nernstian behavior over very wide NO 2 − ion concentration ranges (1.0×10 −6 −1.0×10 −1 M for the PME and 5.0×10 −8 −5.0×10 −2 M for the CGE based on the p ‐isopropyl derivative) and very low detection limits (8.0×10 −7 M for the PME and 2.0×10 −8 M for the CGE). The potentiometric response is independent of the pH of solution in the pH range 4.5–7.0. The electrodes manifest advantages of relative long lifetime, fast response and, most important, good selectivities relative to a wide variety of inorganic and organic anions. In fact the selectivity behavior and detection limit of the proposed NO 2 − ion‐selective electrodes show great improvements compared to the previously reported electrodes for nitrite ion. The proposed PMEs and CGEs can be used for at least 2 and 4 months, respectively, without any divergence in potentials. The electrodes were successfully applied to the determination of nitrite ion in different real samples such as sausage, milk, flour and cheese.