Oxidation of Good's buffers by hydrogen peroxide

Good's zwitterionic buffers are widely used in biological and biochemical research in which hydrogen peroxide is a solution component. This study was undertaken to determine whether Good's buffers exhibit reactivity toward H2O2. It is found that H2O2 oxidizes both morpholine ring-containing buffers (e.g., Mops, Mes) and piperazine ring-containing zwitterionic buffers (e.g., Pipes, Hepes, and Epps) to produce their corresponding N-oxide forms. The percentage of oxidized buffer increases as the concentration of H2O2 increases. However, the rate of oxidation is relatively slow. For example, no oxidized Mops was detected 2 h after adding 0.1 M H2O2 to 0.1 M MOPS (PH 7.0), and only 5.7% was oxidized after 24 h exposure to H2O2. Thus, although all of these buffers can be oxidized by H2O2, their slow reaction does not significantly perturb levels of H2O2 in the time frame and at the concentrations of most biochemical studies. Therefore, the previously reported rapid loss of H2O2 produced from the ferroxidase reaction of ferritin is unlikely due to reaction of H2O2 with buffer, a conclusion supported by the fact that H2O2 is also lost rapidly when the solution PH of the ferroxidase reaction is controlled by a PH stat apparatus in the absence of buffer. (c) 2005 Elsevier Inc. All rights reserved.