Method validation in relation to accuracy and precision for the gas chromatography–mass spectrometric analysis of 19-nortestosterone in urine with heptafluorobutyric anhydride and N-methyl-N-(trimethylsilyl)trifluoroacetamide

Abstract

Method validation for all the analytical methods used in food control is of the highest priority. For this control there is a lack of reference materials, thus, it is necessary to validate the methods each time they are used for new applications. Among the many aspects of validation, this report pays particular attention to repeatability and reproducibility. The within-assay variability gives a good indication of the precision of the method shown by the repeatability. The between-assay variability gives no indication on the accuracy (or trueness) because no certified reference material is available. The reproducibility however, also gives an indication of the precision of the method. In this work the limit of detection, also an aspect of validation, was found to be below 0.375 µg l^–1 for both derivatization methods; however, the precision of the heptafluorobutyric anhydride method was found to be better than that of the N-methyl-N-(trimethylsilyl)trifluoroacetamide method.