Electrochemical determination of SrFe12O19 impurity in perovskite ferrites

•High sensitivity of coulometric titration technique to SrFe12O19 impurity is shown.•A data processing method was developed to determine the amount of impurities.•The method allows oxygen content data recovery from the contamination effect.•The method was successfully verified on the example of NdxSr1−xFe0.8Mo0.2O3−δ data.