Raw material enzymatic activity determination: a specific case for validation and comparison of analytical methods--the example of superoxide dismutase (SOD).

Implementation of ICH guideline for validation of analytical methods was tested in the case of two enzymatic assays of determination of superoxide dismutase (SOD) activity. Analytical figures of merits of two tested methods (NBT reference method and the so called WST-1 method) demonstrate the feasibility of such approach. Nevertheless specification usually admitted for physicochemical method (e.g., HPLC), needs to be clearly enlarged, for instance, up to 10% for repeatability and 20% for reproducibility. On the other hand, the cross-validation performed between the two enzymatic activity determination techniques, though based on the same principle, clearly shows that the quality of results depends on small variation in the experimental conditions. This shows that an enzymatic activity determination should be strictly related to the technique used, especially in the pharmaceutical control quality field, and confirms that analytical figures of merits are strongly function of the technique used. Finally, it was demonstrated that both NBT reference method and WST-1 method give strictly similar results.