scope:

NEN-EN 16936 presents a method describing the screening on the antibiotics tylosin, virginiamycin, spiramycin, bacitracin-zinc and avoparcin at sub-additive levels in complete feeding stuffs and milk replacers by a microbiological 3-plate test. The limit of detection of the method is 1 mg/kg for avoparcin, tylosin, spiramycin and virginiamycin, and 5 mg/kg for zinc bacitracin. The presence of other (veterinary) antibiotics may interfere with the method. Furthermore, high concentrations of metals (Cu, Zn) may interfere. The method should be used as a qualitative screening method. Positive results can be analysed further by TLC; for confirmatory purposes LC-MS is required. A lower limit of detection for zinc bacitracin (3 mg/kg) is achievable, but should be established with an in house validation first.