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 H(2)O(2). It is found that H(2)O(2) 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 H(2)O(2) increases. However, the rate of oxidation is relatively slow. For example, no oxidized Mops was detected 2h after adding 0.1M H(2)O(2) to 0.1M Mops (pH 7.0), and only 5.7% was oxidized after 24h exposure to H(2)O(2). Thus, although all of these buffers can be oxidized by H(2)O(2), their slow reaction does not significantly perturb levels of H(2)O(2) in the time frame and at the concentrations of most biochemical studies. Therefore, the previously reported rapid loss of H(2)O(2) produced from the ferroxidase reaction of ferritin is unlikely due to reaction of H(2)O(2) with buffer, a conclusion supported by the fact that H(2)O(2) is also lost rapidly when the solution pH of the ferroxidase reaction is controlled by a pH stat apparatus in the absence of buffer.