Highly selective PVC-membrane electrodes based on three derivatives of (Tetraphenylporphyrinato) cobalt(III) acetate for determination of trace amounts of nitrite ion

摘要

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 NO2- ion concentration ranges (1.0 x 10(-6) - x 10(-1) M for the PME and 5.0 x 10(-8) - 5.0 x 10(-2) M for the CGE based on the p-isopropyl derivative) and very low detection limits (8.0 x 10(-7) M for the PME and 2.0 x 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 NO2- 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. [References: 55]