AMPEROMETRIC DETERMINATION OF PEROXIDES BY GLASSY-CARBON ELECTRODES MODIFIED WITH COPPER-PHENANTHROLINE COMPLEXES

An amperometric sensor is described for the determination of peroxides in both aqueous and organic media. It consists of a rotating glassy c arbon electrode modified by coating first with a thin film of a perflu orinated anionic exchanger (Tosflex) and then by immobilizing on this substrate the mixed-ligand copper complex [CuL(2)](2+) with 1,10-phena nthroline and bathophenanthroline (i.e., 1,10-phenanthroline containin g two phenyl-sulfonic groups as substituents in the positions 4 and 7) , thanks to the bonds formed between the -NR(3)(+) cationic groups of the Tosflex coating film and the -SO3- anionic groups present in the l atter ligand. The modified electrode, which is rather stable with time and can be easily restored, permits detection of peroxides by their r eduction at less cathodic potentials than at an unmodified electrode s urface, It shows enhanced sensitivity in a variety of media (water, et hanol and ethanol-toluene 60/40 v./v.) which were investigated in view of their ability, on the whole, to dissolve peroxides originally pres ent in different natural samples. Its satisfactory performance, which is unaffected by the presence of oxygen in the sample, in all the medi a studied is reported for hydrogen peroxide and tert-butyl hydroperoxi de in terms of detection limits, dynamic ranges and response time. Its application to the direct determination of peroxides in some cereal o ils was also attempted and the results found are compared with those o btained by conventional methods.