HPHCs-validation of method: limitations in the “accuracy profile”
Analytical results must be both reliable and comparable, because they are often submitted and interpreted for regulatory purposes. Therefore, it is increasingly necessary for analysts to validate analytical procedures and to estimate the uncertainty associated with the results provided by the procedure.
Some requirements of the methodology of the “accuracy profile” are the sample selection, the choice of the matrices and the reference value. Some constraints during HPHC testing of tobacco and smoke are the limited number of certified reference materials having a high level of traceability and standardized methodologies for analysis. Additionally it is quite difficult to find a matrix that is free of the target analyte. As a result, the analyst often has to resort to references with a lower level of traceability, such as spiked samples.
A combination of these factors means that the methodology of the accuracy profile is used to the extreme limit of its original intention, and so it makes sense to look at the applicability. The following parameters were therefore determined: limit of detection, of quantification, limits of the tolerance interval, precision, recovery and measurement uncertainty, using the concept of accuracy profile for benzo[a]pyrene in tobacco; heterocyclic amines, polyaromatic hydrocarbons and caffeic acid in smoke.
The consequences of the selection of the matrices on the calculated Tolerance Interval will be described to confirm that the methods are fit for the intended use.
 NF V03-110 (2010) Analyse des produits agricoles et alimentaires - Protocole de caractérisation en vue de la validation d'une méthode d'analyse quantitative par construction du profil d'exactitude.