Synthesis, characterisation and preliminary analytical evaluation of three oxamide reagents for peroxyoxalate chemiluminescence

The synthesis, characterisation and preliminary analytical evaluation of three oxamide reagents, for peroxyoxalate chemiluminescence, are described. The analytical figures of merit for the three oxamides were assessed using flow injection analysis and the fluorophores rhodamine B and fluorescein in a solvent mixture consisting of tetrahydrofuran, acetonitrile and aqueous buffer (1+1+2 by volume). The calibration functions approached linearity and the best detection limit (for both analytes) was 2 x 10-9M when using the oxamide 2,2'-oxalyl-bis[(trifluoromethanesulfonyl)imino]ethylene-bis(N- methylpyridinium)trifluoromethanesulfonate. These results were found to compare favourably with those obtained for, the popular peroxyoxalate chemiluminescence reagent, bis(2,4,6-trichlorophenyl) oxalate (TCPO), using an identical solvent system. However, the detection limits achieved with TCPO were degraded at pH 10 due to a significant increase in the background emission. The addition of the base catalyst, imidazole, to these chemiluminescent reactions resulted in the deterioration of analytical performance for both TCPO and the oxamide reagents.