Although the use of chloramphenicol (CAP) as a veterinary drug is banned in the European Union and many other countries, monitoring for CAP residues in food is routine. Positive detections are few, but taken extremely seriously. European Union laboratories analysing for CAP should validate methods according to European Commission Decision 2002/657/EC, must be accredited to ISO 17025, and will generally participate in proficiency testing (PT) schemes, such as those offered by the Food Analysis Performance Assessment Scheme (FAPAS®). The FAPAS PTs aim to cover a wide range of relevant matrices including honey, prawns, fish, milk and kidney. Test materials are prepared either by animal dosing studies or by spiking raw matrix. The most common method reported by FAPAS participants used to screen for CAP residues is LC-MS/MS, but ELISA kits are increasingly being used. A recent PT round highlighted that the result obtained might be correlated with the type of analytical method being employed. Follow-up investigations have demonstrated that some of these variations in data are a function of the different stereoisomeric forms of CAP. This paper discusses the implication of this research on method validation requirements and European Union legislation.
Hundreds of food chemistry proficiency tests are carried out annually across the world. The protocols for these are well established. Very occasionally, the data associated with a proficiency test are unexpected in relation to the dispersion or distribution. This may reflect differences between the test material characterisation data and the participants' data in terms of repeatability and reproducibility. The dispersion of participants' data could also reflect a difficulty with a particular analyte/matrix combination. There might also be some unanticipated chemistry occurring in a test material. In all circumstances, there are means of characterising the differences in order to obtain an appropriate outcome for the test. This paper describes some of these differences, observed from a food chemistry proficiency testing scheme.
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