Analytical methods for the analysis of nitroimidazoles, nitrofurans and corticosteroids with LC–MS/MS have been validated by fortifying blank samples below and above the MRPL. CCα and CCβ were calculated using the ISO 11843 approach. In addition, the frequency of methodical compliance for the qualitative criteria was determined at each concentration level. It was observed that at the calculated CCα and CCβ levels the qualitative criteria were not fulfilled. It was concluded that the detection capability of the analytical method should be calculated by using decreasing fortification levels at and below the MRPL.
A protocol validating methods for banned substances by limiting the number of samples is presented and the qualitative criteria for the assessment of CCα and CCβ were verified based on the same set of data without the need of performing additional validation experiments.