Qualitative or quantitative methods for residue analysis

Abstract Qualitative methods are used for illegal drugs (e.g. hormones) which have a so-called zero tolerance (i.e. the presence of even a very small amount is not tolerated). In practice a limit of determination is used to prove the presence or absence of an analyte. Quantitative analysis is necessary especially for residues with a maximum residue limit (MRL). The method used in this case must have a limit of quantification (much) lower than the MRL. In any case, quality criteria must be fulfilled before quantification. In this investigation the pro's and con's of different strategies towards the use of qualitative and quantitative methods are discussed from the point of view and the daily experience of routine control in two field laboratories and one national reference laboratory.