Surface plasmon resonance biosensor screening of poultry liver and eggs for nicarbazin residues Original Research Article

Nicarbazin is used globally as a feed additive to prevent outbreaks of coccidiosis in broiler chickens. The drug is comprised of a complex of two compounds: 4,4′-dinitrocarbanilide (DNC) and 2-hydroxy–4,6-dimethylpyrimidine (DHP). In 1998, The Joint Expert Committee on Food Additives (JECFA) imposed a maximum residue limit (MRL) of 200 μg kg−1 for DNC, the marker residue, in broiler chickens. Nicarbazin is not licensed for use in egg-laying chickens. An assay was developed for DNC using a Biacore® surface plasmon resonance (SPR) biosensor. Antiserum was raised in a rabbit to a structural mimic of DNC. Another DNC mimic was immobilised onto a CM5 sensor chip. Binding of the antibody to the chip surface could be detected and was inhibited by the presence of DNC. The chip surface was regenerated using a combination of base and organic solvent and was highly stable over many hundreds of sample injections. A single analytical cycle (sample injection, chip regeneration and system wash) took 7 min to complete. Prior to analysis, nicarbazin was extracted from liver and egg samples using acetonitrile. Liver samples required an additional hexane wash. Limits of detection (3 σ) for liver and eggs were 17 and 19 ng g−1, respectively. A comparison of DNC concentration in livers (n=8) taken from broilers treated with nicarbazin showed a high correlation (r2=0.88) between liquid chromatography (LC) and SPR biosensor results.