A method is described for definition of peracids in the presence of hydrogen-peroxide in a solution with the following steps:(1) introducing an electrode-design, which provides at least one measurement electrode and one counter electrode into the solution,(2) Loading of the electrodes with varying potentials; and(3) Measurement of the current by using a measurement electrode.With such a method the peracid solutions always contain hydrogen-peroxide, which also shows similar reactions.In order to determine the peracid concentration, a value of the determined current is compared with a corresponding value of an earlier recorded electrode-design.