Evaluation of lophine derivatives as chemiluminogens by a flow-injection method

A rapid and convenient method for the evaluation of lophine (2,4,5-triphenylimidazole) derivatives as to their chemilumi-nescence efficiency was developed by using a flow-injection technique. Standard solutions of lophine derivatives were injected into a flow line containing a carrier solution (1.5 × 10−4 M cobalt(II) containing 0.2% hydroxylammonium chloride in 75% methanol), which was successively combined with a flow line containing 100 mM hydrogen peroxide in H2O and a flow line containing 1.0 M KOH in H2O, and the chemiluminescence generated was monitored. Addition of hydroxylammonium chloride into a carrier solution resulted in a significant increase in chemiluminescence. Calibration graphs for eighteen derivatives were prepared and the relative chemiluminescence intensities were estimated from the slopes of these graphs. Among the derivatives, the compounds substituted by OCH3 at the 2- and 3-positions, and COOH, COC1, CONHNH2 and CONHNHCO(CH2)4CH3 at the 4-position on the phenyl ring at the 2-position of the imidazole skeleton showed large chemiluminescence intensities which are comparable to that of lophine. The detection limit of lophine was 72 fmol per injection at a signal-to-noise ratio of 2.