The principle of ECLong is based on chemiluminescence and is very convenient to detect the Horseradish peroxidase (HRP) activity in many assays such as Western blotting, Southern blotting, and Northern blotting. HRP catalyzes the chemiluminescent oxidation of cyclic diacylhydrazides such as luminol by
hydrogen peroxide (H₂O₂). ECLong can enhance the luminol-dependent chemiluminescence and be wildly used to detect the present of HRP-conjugated antibodies or streptavidin which binding to antigen or nucleotide sequence respectively.