Chemiluminescent determination of luminol and hydrogen peroxide using hematin immobilized in the bulk of a carbon paste electrode

A new method for immobilization of a chemiluminescent reagent is presented. It is based on immobilizing hematin, a catalyst for luminol reaction, in t he bulk of a carbon paste electrode. Bulk-immobilization allows renewal of the surface by simple polishing or cutting to expose anew and fully active surface in the case of fouling or deactivation by other means. By using a h ematin-modified carbon paste electrode, the applied potential shifted negat ively compared with that of unmodified carbon paste electrode or a glassy c arbon electrode. The shift in potential changed the reaction processes and effectively stabilized the chemiluminescent signal during successive measur ements. Under this condition, the signal was stable during 3 hours of conti nuous operation. The log-log plots of the emitted light intensity vs. lumin ol concentration and hydrogen peroxide concentration were linear over the r egion 10(-8)-10(-3) mol L-1 with a correlation coefficient of 0.999 and 3.9 x 10(-6)-10(-3) mol L-1 with a correlation coefficient of 0.994, respectiv ely. Application of this method for other chemiluminescent and bioluminesce nt systems is suggested.