Nitrate-selective electrodes based on meso-tetrakis[(2-arylphenylurea)-phenyl]porphyrins as neutral lipophilic ionophores.

Polymeric-membrane electrodes for NO(3)(-) anion based on (alpha,alpha,alpha,alpha)-5,10,15,20-tetrakis [2-(4-methylphenylurea)phenyl]porphyrin I and similar urea-functionalized porphyrins II-IV as neutral ionophores were prepared. The effects of polymeric-membrane composition and test solution pH were tested. The electrodes revealed good selectivity coefficients for NO(3)(-) over a wide variety of other anions, and the values of eight anions were measured. Of the various electrodes prepared, the electrode based on urea-functionalized porphyrin I exhibits a linear stable response over a wide concentration range (1.0x10(-5) to 1.0x10(-1)) with a slope of -57.4mV per decade, a detection limit of log[NO(3)(-)]=-5.72, and a selectivity coefficient for nitrate against perchlorate anion (log K (NO (3)(-),j)(pot )=-1.81 ).