OXIDATIVE CHEMILUMINESCENCE OF SOME NITROGEN NUCLEOPHILES IN THE PRESENCE OF FORMIC-ACID AS AN ANCILLARY REDUCTANT

Chemiluminescence signals were obtained when aqueous propan-2-ol solut ions of phenylhydrazine, 2-nitrophenylhydrazine, 4-nitrophenylhydrazin e, 2,4-dinitrophenylhydrazine and hexanal oxime or aqueous solutions o f hydroxylamine and dimethylglyoxime were injected into a carrier stre am of formic acid which merged with acidified potassium permanganate s olution, Rhodamine-B was present in the carrier stream as a sensitiser . The chemiluminescence was deduced to originate from the oxidation of the hydrazine or amine functional groups, For phenylhydrazine oxidati on, dinitrogen was proposed as the emitting molecule; in the oxidation of hydroxylamine, a nitrogen oxide emitter was proposed, The role of the formic acid was as a source of formate ions, which are oxidised to carbon dioxide in a relatively slow reaction, It is further proposed that excited carbon dioxide molecules, as well as producing a feeble e mission in what seems to be an autocatalytic reaction, transfer energy to the emitting products of analyte oxidation, thus enhancing their c hemiluminescence. Injection of formate ions, or their massive producti on by injections of strong alkali, cause chemiluminescence signals whi ch would interfere with those from the analyte, Iron salts, which cata lyse the permanganate-formic acid reaction, have a similar effect but at much lower concentrations.