title: Enzyme immunoassay for semicarbazide--the nitrofuran metabolite and food contaminant.
abstract: Semicarbazide (SEM), the marker residue for the banned nitrofuran veterinary antibiotic nitrofurazone (NFZ), has been detected regularly in foods (47% of recent nitrofuran EU Rapid Alerts involve SEM). However, the validity of SEM as a definitive marker for NFZ has been undermined by SEM arising from other sources including azodicarbonamide, a plastics blowing agent and flour treatment additive. An inexpensive screening test for SEM in food matrices is needed--all SEM testing currently uses expensive LC-MS/MS instrumentation. We now report the first production of antibodies against derivatised SEM. A novel carboxyphenyl SEM derivative was used to raise a polyclonal antibody that has been incorporated into a semi-quantitative microtitre plate ELISA, validated according to the criteria set out in Commission Decision 2002/657/EC, for use with chicken muscle. The antibody is highly specific for derivatised SEM, cross-reactivity being 1.7% with NFZ and negligible with a wide range of other nitrofurans and poultry drugs. Samples are derivatised with o-nitrobenzaldehyde and simultaneously protease digested before extraction by cation exchange SPE. The ELISA has a SEM detection capability (CCbeta) of 0.25 microg kg(-1) when a threshold of 0.21 microg kg(-1) is applied to the selection of samples for confirmation (lowest observed 0.25 microg kg(-1) fortified sample, n=20), thus satisfying the EU nitrofurans' minimum required performance limit of 1 microg kg(-1). NFZ-incurred muscles (12) containing SEM at 0.5-5.0 microg kg(-1) by LC-MS/MS, all screened positive by this ELISA protocol which is also applicable to egg and chicken liver.
authors.affiliation: Queen's University Belfast, Department of Veterinary Science, Northern Ireland, UK.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Cooper
authors.forename: Jeanne V
authors.initials: JV
authors.lastname: Samsonova
authors.forename: Laura
authors.initials: L
authors.lastname: Plumpton
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Elliott
authors.forename: D Glenn
authors.initials: DG
authors.lastname: Kennedy
mesh_terms: D002853:Chromatography, Liquid; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005506:Food Contamination; D009581:Nitrofurans / Q000378:metabolism*; D015203:Reproducibility of Results; D012663:Semicarbazides / Q000032:analysis*; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry
chemical_list: D009581:Nitrofurans; D012663:Semicarbazides; C010059:carbamylhydrazine