Luminol capable of generating electrochemical luminescence was employe
d as a label of immunoassay. A luminol-labeled antibody generated lumi
nescence upon anodic oxidation and the luminescence decreased markedly
in the presence of antigen. The decrease was correlated to the antige
n concentration as low as 10(-11) g/ml antigen. The proposed method wa
s operated in an optoelectrochemical cell. A miniaturized and sensitiv
e immunosensing can be developed by fabricating a small cell with a ve
ry thin layer.