Abstract
An inter-laboratory validation was carried out to determine the performance characteristics of an analytical method based on thin-layer chromatography (TLC) coupled to microbiological detection (bio-autography) for screening feed samples for the presence of spiramycin, tylosin and virginiamycin. Twenty-four samples including blank samples and samples with concentrations of the target analytes ranging between 1 and 5 mg kg−1 (expressed in microbiological activity) were analysed by seven laboratories participating in the study. The required detection limit was 1 mg kg−1 (expressed in microbiological activity). For spiramycin, acceptable values for the sensitivity (at least 95%) indicating the rate of correct positive results were obtained for samples containing this substance at or above 2 mg kg−1, whereas at 1 mg kg−1, the sensitivity rate dropped to about 70%. Therefore, it was concluded that the detection limit was 2 mg kg−1. For tylosin and virginiamycin, acceptable values of the sensitivity were obtained for all concentrations including 1 mg kg−1. Therefore, the method fulfils the criterion regarding the required sensitivity at the target detection limit for tylosin and virginiamycin.
Acknowledgements
The authors would like to thank the different institutes participating in this ring trial, more specifically: DGCCRF-L35 (Rennes, France); Bayerisches Landesamt für Gesundheid und Lebensmittelsicherheit (Oberschleissheim, Germany); LUFA-ITL (Kiel, Germany); LUFA Dep. Microbiology (Speyer, Germany); Istit. Zoo. Sper. Lobardia E. Romagna. Bromat. Feeds Lab. (Brescia, Italy); AGES (Vienna, Austria); and EZN INIAP (Vale de Santarem, Portugal). The SIMBAG-FEED project was funded by the European Commission, Direction General RTD, 5th Framework Programme, Competitive and Sustainable Growth (GROWTH) Programme, Measurements and Testing Generic Activity, Contract No. G6RD-CT-2000-00413. The authors are also very grateful to Gerald Kramer (IRMM) and Hakan Emteborg for the test samples prepared within this project and utilized in the present study.