VETERINARY DRUG RESIDUES Validation of a Biacore Method for Screening Eight Sulfonamides in Milk and Porcine Muscle Tissues According to European Decision 2002/657/EC VALÉRIE GAUDIN,CÉLINE HÉDOU, and PASCAL SANDERS Community Reference Laboratory for Antimicrobial Residues in Food, Agence Française de Sécurité Sanitaire des Aliments, Laboratoire d’Etude et de Recherche sur les Médicaments Vétérinaires et Désinfectants, BP 90203, 35302 Fougères, France Sulfonamides are commonly used for prophylactic or therapeutic purposes in veterinary medicine. A maximum residue limit (MRL) for sulfonamides has been set at 100 mg/kg in milk and muscle. A multisulfonamide antibody was used for the development of 2 different Biacore â protocols, one for the screening of milk samples, the other for muscle samples. Two different Biacore systems were used: Biacore X system (milk protocol), which is considered a research and development apparatus, and Biacore 3000 system (muscle protocol), which is a completely automated system used for high-throughput screening. This report describes the validation of semiquantitative immunological methods according to the European Decision 2002/657/EC “concerning the performance of analytical methods.” The different performance characteristics (detection capability CCb, specificity/selectivity, precision, stability, and applicability) were determined in relation to the European Union MRL of 100 mg/kg for sulfonamides. The applicability of the method to porcine, bovine, and poultry muscle was studied. The detection capabilities CCb were calculated to be 40 mg/L in milk and 60 mg/kg in porcine, bovine, and poultry muscles. Eight different sulfonamides, of which 3 (sulfamethazine, sulfamerazine, and sulfadiazine) are authorized in France, were detected simultaneously, at or below the MRL level, with both Biacore systems. S ulfonamides are synthetic antimicrobials currently used for the prophylaxis and therapy of bacterial diseases. Currently, sulfonamides are administered as coccidiostatic agents in poultry and ruminants. In beef cattle, they are used to maintain weight gain and feed efficiency. Sulfonamides potentiated with trimethoprim or ormetoprim are very effective broad spectrum antimicrobials. Nine sulfonamides, namely, sulfamethazine (SMZ), sulfadiazine, sulfadimethoxine, sulfadoxine, sulfaguanidine, sulfa- methoxypyridazine, sulfanilamide, sulfaquinoxaline, and sulfamerazine, are authorized in veterinary medicine in France. In the European Union, the maximum residue limit (MRL) for sulfonamides has been set at 100 mg/kg in milk and in muscle (1). Therefore, an ideal screening method should simultaneously detect the entire family at or below the MRL. A review of the literature methods currently available for screening sulfonamide drug residues in edible tissues and milk presented by Wang et al. (2) includes high-performance liquid chromatography [HPLC; milk (3), honey (4), eggs and animal tissues (5)], liquid chromatography/mass spectrometry (LC/MS), thin-layer chromatography (6, 7), gas chromatography (GC), enzyme-linked immunosorbent assay (ELISA), Charm II® tests (8), biosensors [Biospecific Interaction Analysis (BIA); 9–12] and microbiological methods (13–15). LC methods were able to detect several sulfonamides (from 8 to 21 different sulfonamides) in the same run, at or below the MRL level. However, considering their high cost and the need for skilled technicians, physicochemical methods (GC, HPLC, LC/MS) are more suitable for confirmatory analysis than screening methods. Although microbiological methods often lack sensitivity, immunoassays are very useful for the screening of veterinary drugs because they are generally simple, quick, sensitive, and cost-effective. In the past, when immunological methods were developed for the screening of sulfonamides, the antibodies (generally polyclonal) were very specific (16–19). However, targeted ELISA tests were not suitable for multiresidue screening of MRL substances. SMZ has generally been the target sulfonamide, probably because it is currently used in many countries. Several methods have been developed in different laboratories for the screening of SMZ in different matrixes: milk (9–11), pig bile (20, 21), pig bile and urine (22), and pig muscle (12). Because of the very promising results obtained with a monoclonal antibody Mab 21C7 in our laboratory, we decided to develop in-house 1706 GAUDIN ET AL.:JOURNAL OF AOAC INTERNATIONAL VOL. 90, NO. 6, 2007 Received February 20, 2007. Accepted by JB July 19, 2007. Corresponding author's e-mail: v.gaudin@fougeres.afssa.fr Downloaded from https://academic.oup.com/jaoac/article/90/6/1706/5657935 by guest on 20 September 2021