Iodophenol blue-enhanced luminol chemiluminescence and its application to hydrogen peroxide and glucose detection

In this study, we found that iodophenol blue can enhance the weak chemiluminescence (CL) of luminol-H2O2 system. With the aid of CL spectral, electron spin resonance (ESR) spectral measurements and studies on the effects of various free radical scavengers on the iodophenol blue-enhanced luminol-H2O2 system, we speculated that iodophenol blue may react with H2O2 and oxygen to produce oxidizing radical species such as OH(•) and O2(•-) resulting the formation of (1)O2. The generated (1)O2 may react with luminol anion generating an unstable endoperoxide and subsequent 3-aminophthalate* (3-APA*). When the excited-state 3-APA returned to the ground-state, an enhanced CL was observed. Based on the H2O2 concentration dependence of the catalytic activity of iodophenol blue, a cheap, simple, sensitive CL assay for the determination of H2O2 was established. Under the optimum experimental conditions, a linear relationship between the relative CL intensity and H2O2 concentration in the range of 0.025-10 μM was obtained. As low as 14 nM H2O2 can be sensitively detected by using the proposed method. The relative standard deviation for 5, 1 and 0.25 μM H2O2 was 2.58%, 5.16% and 4.66%, respectively. By combining the glucose oxidase (GOx)-catalyzed oxidation reaction, CL detection of glucose was realized. The linear range of glucose detection was 0.1-30 μM with a detection limit of 0.06 μM. The proposed method has been applied to the detection of glucose in diluted serum.