1. Centre for Veterinary Drug Residues,Canadian Food Inspection Agency, 116 Veterinary Rd, Saskatoon,SK, S7N 2R3, Canada
2. State Institute for Quality Control of Agricultural Products (RIKILT-DLO), PO Box 230, 6700 AE Wageningen, The Netherlands
3. Centre for Veterinary Drug Residues, Canadian Food Inspection Agency, 116 Veterinary Rd, Saskatoon,SK, S7N 2R3, Canada