Sudan dyes are banned to be used in food additives because of the carcinogenicity of their metabolites. A rapid and sensitive indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed to detect the residues of Sudan dyes. Novel immunogen and coating antigen were synthesized via glutaraldehyde linking. The hapten-bovine serum albumin (BSA) was applied as immunogen and the hapten-ovalbumin (OVA) was served as coating antigen. The monoclonal antibody obtained showed high sensitivity to Sudan I with an IC(50) value of 1.7 μg L(-1) in buffer and was suitable to detect the residues of Sudan red in food products. The specificity of the assay was studied by measuring cross-reactivity of the antibody with the structurally related compounds of Sudan II (<1%), Sudan IV (<1%) and para red (120%). Chilli jam and chilli oil samples spiked with Sudan dyes were analyzed by the method. The detection limit (LOD) of the ELISA method applied in chilli jam and chilli oil was 9.0 μg L(-1) and 19.6 μg L(-1), respectively. The recovery rates of Sudan-I in chilli oil and chilli jam were in the range of 80%-110% with coefficients of variation <25%. The intra-assay variation and inter-assay variation in buffer were both <9%.

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Conjugates between bovine serum albumin and (R,S)-2-aminonicotine were produced, and these conjugates were employed in rabbits and goats for the production of nicotine antibodies. In the assay of nicotine, an 1251-tyrosine methyl ester derivative of (R, S)-6-aminonicotine was employed as radioligand. The antibody-bound derivative was separated from the free derivative by charcoal adsorption (0.5 % charcoal, 0.1 % dextran T-70, 0.1 % bovine serum albumin, pH 7.3). Among the twenty five nicotine derivatives and metabolites examined, (R, S)-6-aminonicotine gave the highest cross-reaction. Cross-reaction with cotinine, a major mammalian metabolite of nicotine, was less than 0.1 % for both the rabbit-derived and goat-derived antisera. Cross-reaction by other metabolites, such as (5')-nicotine-"-oxide, (5')-nornicotine, and N-methylpyrrolidine was less than 1 %.The antibodies produced were thus highly specific to nicotine. The radioimmunoassay for nicotine showed a maximum sensitivity of 10 ng/ml in 5O-pl plasma samples for both antisera. After the smoking of a single cigarette (1.2 mg nicotine content in mainstream) the peak blood plasma level of nicotine in the subjects varied from 20 -104 ng/ml, and high levels of nicotine were not necessarily found in heavy smokers.Interest in the metabolism of nicotine has been stimulated during the past two decades by an increased consideration of the possible role of nicotine as a reinforcer [I] in the habitual use of tobacco and by many studies on the short half-life of nicotine in human blood plasma [2-41. In addition, some of the metabolites of nicotine appear [5-71 in various instances physiologically to oppose or enhance the effects of nicotine. These and other factors have combined to focus our attention on effective methods for determining the kinetic factors in the biodisposition of nicotine. Basic to a general understanding of this biodisposition has been a general need for rapid and accurate determinations of nicotine and its metabolites in biological material. This need has been met in part by gas chromatography and combined gas chromatography/mass spectrometry. Limitations and advantages of these and other methods have been previously reviewed [8,9]. Attention in our laboratories [lo, 111 and those of others [12-151 has been directed, therefore, to various immunological techniques for the rapid determination of nicotine.The low molecular weight of nicotine and the extremely limited tendency of the alkaloid to form stable molecular linkages with many macromolecules has dictated strongly against the possibility of producing nicotine antisera of useful titer by employing the parent alkaloid as the immunogen, and functionalization of nicotine has been necessary. In functionalizing nicotine prior to coupling with macromolecules for antibody production, both the pyridine ring and the pyrrolidine ring of the alkaloid are available. In particular, our early and recent attention has been devoted to 2-aminonicotine and 6-aminonicotine as functionalized haptens, since, as oth...

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Ronidazole was used as the starting material to prepare an immunogen and coating antigen. An anti-nitroimidazole monoclonal antibody was produced and an indirect competitive ELISA was established to detect nitroimidazole compounds in food products. The IC(50) values were determined to be 0.20 ng/ml for metronidazole, 4.0 ng/ml for tinidazole, 0.17 ng/ml for dimetridazole and 0.24 ng/ml for ornidazole. Considering that nitroimidazoles were commonly used as veterinary drugs, nitroimidazole residues in food products of animal origin were detected by the method. The coefficient of variation for nitroimidazoles determination in contaminated chicken, chicken liver and shrimp were all <14% and the recovery rate was in the range 74.0-90.6%. The results proved that the developed method was successful in detecting nitroimidazoles in food products.

Abstract:To detect gatifloxacin (GAT) residue in swine urine, an electrochemical immunoassay was established. An indirect competitive immunoassay was developed, in which the coating antigen is immobilized in an enzyme-linked immunosorbent assay (ELISA) plate and GAT residue from the sample competes with the limited binding sites in added anti-GAT antibody. Horseradish peroxidase (HRP) conjugated to goat anti-rabbit IgG was used as the enzymatic label. A carbon fiber working electrode was constructed and current signals were detected by using hydrogen peroxide as a substrate and hydroquinone as an electrochemical mediator. The electrochemical immunoassay was evaluated by analysis of GAT in buffer or swine urine and an average value of half inhibition concentration (IC 50 ) of 8.9 ng/ml was obtained. Excellent specificity of the antibody was achieved with little cross-reaction with lomefloxacin (3.0%), ciprofloxacin (3.0%), and ofloxacin (1.9%) among commonly used (fluoro)quinolones. In conclusion, the immunoassay system developed in this research can be used as a rapid, powerful and on-site analytical tool to detect GAT residue in foods and food products.