A magnetic electrode modified with hemoglobin for determination of hydrogen peroxide: distinctly improved response by applying a magnetic field.

A facile and highly sensitive biosensor was developed for the determination of hydrogen peroxide (H2O2) via electrochemical catalytic reduction of H2O2 by hemoglobin (Hb). Hb was enriched and immobilized simply in a chitosan (Chit) membrane on a magnetic electrode to construct an enzyme-like biosensor. The biosensor catalyzes the electrochemical reduction of H2O2 under an external magnetic field. The response improved roughly twice as Hb was adsorbed by Chit in an alkaline medium. The response of the biosensor under the magnetic field increased by 16% owing to the paramagnetism of Hb. The effect of pH values on Hb adsorption by Chit, as well as the effect of an external magnetic field on Hb configuration were investigated by UV-vis spectroscopy. The reduction peak current has linear and log-linear relationships with H2O2 concentration in the range of 5-250 μmol∙L-1 and 0.01-1 μmol∙L-1, respectively. The detection limit was 0.003 μmol∙L-1, with a good sensitivity of 0.227 μA∙μM-1∙cm-2. The biosensor was successfully applied to the determination of H2O2 in milk samples and in disinfectant solutions. Recoveries ranged from 96.3 to 105.4%, and from 95.3 to 107.7%, respectively. Graphical abstractConstruction of the biosensor, and principle of H2O2 determination based on Hb bioelectrocatalysis.