POSTULATION OF A PHENOXYL RADICAL INTERMEDIATE AS THE SPECIES RESPONSIBLE FOR THE BACKGROUND EMISSION OBSERVED WITH CERTAIN PEROXYOXALATE CHEMILUMINESCENCE REAGENTS

We demonstrate that the characteristic background emission spectra ass ociated with certain substituted diaryl oxalates used for peroxyoxalat e chemiluminescence reagents, namely bis(2,4,6-trichlorophenyl)oxalate , (TCPO, 1), bis(2,4-dichlorophenyl)oxalate, (2) and bis(2,6-dichlorop henyl) oxalate, (3), is not observed with either of the two substitute d oxamides, 2,2'-oxatyl-bis[(trifluoromethanesulfonyl)imino] ethylene- bis(N-methylpyridinium) trifluoromethanesulfonate (PETQ) (4), or limin o]ethylene-bis(1-methyl-1-benzylpiperidinium) trifluoromethanesulfonat e, (BPTQ) (5) when utilised under identical chemical conditions, The b ackground emission intensity from TCPO (1) can be significantly enhanc ed by the addition of 2,4,6-trichlorophenol (TCP), Spectrally identica l chemiluminescence is generated upon the reaction of TCP with the two oxamides 4 and 5, Fluorescent spectra obtained from solutions of TCP and hydrogen peroxide confirmed the existence of a transient luminesce nt species, Consequently, a phenoxyl radical has been postulated as th e species responsible for the background emission from TCPO.