Assay of peracid in the presence of excess hydrogen peroxide

A simple and rapid colorimetric method for the determination of peracids in the presence of excess hydrogen peroxide is described. The method is based on the selective destruction of hydrogen peroxide by the enzyme catalase, a procedure which leaves the peracid unaffected. The residual solution then containing only peracid, can be assayed using the stoichiometric oxidation of 2,2'-azino-bis-(3-ethyl-benzthiazoline-6-sulfonate) diammonium salt (ABTS) in the presence of peroxidase, a reaction that can be quantified photometrically at 405 nm. The double-enzyme method was extended to microtiter plate-based systems, thus providing an easy way of analyzing multiple samples for their peracid content.