484 CHEMICAL SENSORS. VOLUME 5: ELECTROCHEMICAL AND OPTICAL SENSORS 2.2.3. Peroxyoxalate Chemiluminescence Peroxyoxalate chemiluminescence (POCL) was first introduced by Chandross et al. in 1963. They found a bright chemiluminescence when the reaction was carried out by adding the acid chloride to hydrogen peroxide containing a fluorescent compound (fluorophore) such as anthracene, 9,10-diphenylanthra- cene, or N-methylacridone. The POCL reaction involves hydrogen peroxide oxidation of an aryl oxalate ester in the presence of a fluorophore. Therefore, it can be used for the detection of a fluorophore or hydrogen peroxide. In the POCL reaction, the elimination of an exciting light source, which is used in the fluorescence detection, reduces background emission or light-source instability, and the sensitivity thus improves to 10- to 100-fold over the fluorescence. Because of the high selectivity and sensitivity of the POCL reaction system combined with flow injection analysis (FIA) or high-performance liquid chromatography (HPLC), numerous applications for the determination of analytes have been reported (Tsunoda et al. 2005). 3. METHODOLOGY OF CHEMICAL ANALYSIS USING CHEMILUMINESCENCE SENSING Chemiluminescence measurement is a very simple procedure, since no excitation radiation is required.