Chemiluminescence detection with a liquid core waveguide: Determination of ammonium with electrogenerated hypochlorite based on the luminol-hypochlorite reaction Original Research Article

A liquid core waveguide (LCW) based chemiluminescence detector, suitable for the measurement of chemiluminescence (CL) reactions, is described in this paper. The LCW acts both as a reaction cell and a light collector and terminates in a conventional, high numerical aperture optical fiber that carries the CL emission to a photomultiplier tube (PMT). The fast CL reaction of luminol with hypochlorite is used to test the performance of the detection arrangement. Ammonia can consume hypochlorite and thus reduces the background CL signal from the luminol-hypochlorite reaction when it is introduced in that reaction system. We introduce here a novel means of electrogenerating hypochlorite, utilizing flow-splitting at the center of a T-shaped electrolytic cell to separate the anodic and cathodic products. When this scheme is used for the determination of ammonium, a limit of detection (LOD) of 120–260 nM NH4+ is achieved with an inexpensive PMT detector and a constant current source.