Results and Conclusions of Validation

Having determined the accuracy, repeatability, and intermediate fidelity for the four analytes dosed by the method for each of the five concentrations, the next step is to construct a table that compiles all the results (see Table 7.6). The acceptance criteria of an analytical method are 20% for accuracy, coefficients of variation less than 15% for repeatability, and less than 25% for intermediate fidelity according to the SFSTP. 

By applying these criteria to the results presented in Table 7.6, we can see that the method is validated on the entire domain of concentrations considered for the COC, AEME, and COET analytes. By contrast, the results for EME do not meet the set criteria. Indeed, the accuracy, repeatability, and intermediate fidelity are 40, 58, and 96%, respectively, at a concentration of 0.05 ng/mg. The intermediate fidelity is 26% at 0.10 ng/mg. The repeatability is 16% at 2.5 ng/mg and 17% at 4.0 ng/mg. 

Estimation of Repeatability and Intermediate Fidelity for Cocaine at a Concentration of 0.5 ng/mg 

Accuracy, Repeatability, and Intermediate Fidelity Results from Quality Control Samples 

Faced with these results, four solutions can be considered. The first involves reconsidering the whole method after having determined the reasons for the validation failure for EME. Was sample preparation not sufficiently selective Was the MS/MS method badly optimized This is the most tedious solution that is only of interest if one has managed to determine the nature of the problem. It is indeed useless to reiterate the validation without correcting all the parameters responsible for the failure of the validation procedure. If the choice is to repeat the validation, the process must be performed again for each of the four molecules, even if the three others satished the validation criteria. The molecules are in mixture and thus susceptible to interaction. Consequently, they cannot be considered independently if they are the objects of the same analytical method. 

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