Determination of Subnanomolar Levels of Hydrogen Peroxide in Seawater by Reagent-Injection Chemiluminescence Detection

A reagent-injection chemiluminescent method for the determination of hydrogen peroxide (H2O2) has been developed. The method is based on the catalytic (cobalt (II)) oxidation of luminol by hydrogen peroxide in an alkaline solution. One mixed reagent is used for the analysis using the reagent injection method. The mixed reagent is optimized for pH and concentration of luminol and Co2+. Apart from Fe2+, none of the 14 species tested showed interference at their seawater levels. Because Fe2+ oxidation is rapid compared to the rate of decay of hydrogen peroxide, the Fe2+ interference can be eliminated by storing seawater samples for 1 h. The combination of reagents and the adaptation of reagent injection lead to a subnanomolar detection limit. The accuracy of the method is at least 0.42 nM. The precision of the method is 17 pM (for a 0.57 nM sample). The method has been used aboard ship to determine the concentrations of hydrogen peroxide in seawater samples in the open ocean as well as on the continental shelf.