Identification of residues by LC-MS. The application of new EU guidelines

New EU guidelines for identification and quantification of organic residues and contaminants are established to guarantee efficient and reliable residue control of prohibited growth promoting agents, e.g. steroids and beta-agonists, and veterinary drugs. Reliability includes the reliability of the identification with spectrometric techniques. The guidelines take into account the implications of a detected violation. The unambiguous identification of a prohibited compound needs more information on the structure of the analyte than the identification of a registered veterinary drug of which the mass fraction detected exceeds the established Maximum Residue Limit. For detection using mass spectrometry this is reflected by the number of fragment ions that must be detected.