Substituted cobalt phthalocyanine complexes as carriers for nitrite-sensitive electrodes

A new poly(vinyl chloride) membrane electrode based on lipophilic 2,9,16,23-tetra-tert-butylphthalocyanine-cobalt is described which demonstrates excellent selectivity toward the nitrite ion. The resulting electrodes displayed a near-Nernstian response for nitrite in the concentration range 10−5-0.1 M with the selectivity sequence nitrite ⪢ thiocyanate ⪢ iodide ⪢ perchlorate ⪢ bromide ⪢ nitrate ⪢ chloride. The UV/Vis spectra and a.c. impedance studies showed that the excellent selectivity for nitrite was related to the unique interaction between the central cobalt ion and nitrite.