Nitrofuran Metabolites Research Articles

Rebuttal to a Comment on New Reagent for Trace Determination of Protein-Bound Metabolites of Nitrofurans in Shrimp Using Liquid Chromatography with Diode Array Detector

ADVERTISEMENT RETURN TO ISSUEPREVCorrespondence/Rebut...Correspondence/RebuttalRebuttal to a Comment on New Reagent for Trace Determination of Protein-Bound Metabolites of Nitrofurans in Shrimp Using Liquid Chromatography with Diode Array DetectorPakawadee SutthivaiyakitView Author Information Department of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Kasetsart University, Bangkok 10900, ThailandCite this: J. Agric. Food Chem. 2009, 57, 23, 11448Publication Date (Web):November 13, 2009Publication History Received20 May 2009Published online13 November 2009Published inissue 9 December 2009https://doi.org/10.1021/jf9031102Copyright © 2009 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views345Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (585 KB) Get e-AlertsSUBJECTS:Animal derived food,Chromatography,Materials,Metabolism,Reagents Get e-Alerts

Comment on New Reagent for Trace Determination of Protein-Bound Metabolites of Nitrofurans in Shrimp Using Liquid Chromatography with Diode Array Detector

Comment on New Reagent for Trace Determination of Protein-Bound Metabolites of Nitrofurans in Shrimp Using Liquid Chromatography with Diode Array Detector

Correction to New Reagent for Trace Determination of Protein-Bound Metabolites of Nitrofurans in Shrimp Using Liquid Chromatography with Diode Array Detector

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTCorrection to New Reagent for Trace Determination of Protein-Bound Metabolites of Nitrofurans in Shrimp Using Liquid Chromatography with Diode Array DetectorSaowapa Chumanee, Somyote Sutthivaiyakit, and Pakawadee Sutthivaiyakit*Cite this: J. Agric. Food Chem. 2009, 57, 20, 9856Publication Date (Web):August 26, 2009Publication History Published online26 August 2009Published inissue 28 October 2009https://doi.org/10.1021/jf902837fCopyright © 2009 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views401Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (569 KB) Get e-AlertsSUBJECTS:Chromatography,Diodes,Metabolism,Reagents Get e-Alerts

Development of a monoclonal antibody-based enzyme-linked immunosorbent assay for detection of the furaltadone metabolite, AMOZ, in fortified shrimp samples

3-Amino-5-morpholinomethyl-2-oxazolidone (AMOZ) is a tissue bound metabolite of furaltadone, a synthetic nitrofuran antibiotic widely used in veterinary practices both to treat infectious diseases and as a growth promoter. Because AMOZ is carcinogenic and poses a potential health hazard for human consumers, its parent compounds, the nitrofurans, are banned from being used in animals destined for human food consumption in various countries. To enforce this, foods are routinely monitored for nitrofuran metabolite residues including AMOZ. Thus, reliable high throughput analytical methods to detect AMOZ have been developed but these are mostly based on chemical analysis. In contrast, sensitive and specific detection methods based on immunoassays for AMOZ using monoclonal antibodies have yet to be established. In this study, we report the generation of two monoclonal antibodies with high specificity for AMOZ and the development of a monoclonal antibody-based ELISA to detect AMOZ in shrimp samples using one of these clones (clone 2E5.1). Clone 2E5.1 yielded the highest sensitivity and specificity and cross reacted solely to furaltadone and AMOZ and not to other antibiotics. Competitive ELISA with 2E5.1 gave IC50 values for AMOZ, CPAMOZ and furaltadone of 5.33, 0.023 and 1.330 ng/ml, respectively. When applied in ELISA to detect AMOZ in fortified shrimp samples, the detection capability and limit of detection were 0.3 and 0.16 μg/kg, respectively. Taken together, a sensitive and specific monoclonal antibody-based ELISA for AMOZ detection has been developed that could facilitate the economic and reliable high throughput monitoring of AMOZ in shrimps and potentially other food.

New Reagent for Trace Determination of Protein-Bound Metabolites of Nitrofurans in Shrimp Using Liquid Chromatography with Diode Array Detector

The synthesis of derivatives of metabolites from furazolidone, furaltadone, nitrofurazone, and nitrofurantoin using a new derivatizing reagent, 2-naphthaldehyde (NTA), is described. The reaction product was used in liquid chromatography with diode array detector (LC-DAD) for determination of protein-bound metabolites of nitrofurans in shrimp followed by two steps of liquid-liquid extraction. Derivatives of nitrofuran metabolites are well separated from NTA remaining in the extract upon separation on a ChromSpher 5 Pesticide (250 x 4.6 mm, 5 microm) column at 40 degrees C with acetonitrile/5 mM ammonium acetate adjusted to pH 7.5 gradient as the mobile phase and DAD detection at 308 nm except for naphthyl derivative of 1-aminohydantoin at 310 nm. The high absorptivity of these derivatives makes simultaneous screening of these metabolites in shrimp at 1 microg/kg possible for the first time using LC-DAD. The method was validated using blank shrimp fortified with all four metabolites at 1, 1.5, and 2 microg/kg. Recoveries were >86% with relative standard deviations of <14% for all four metabolites. Comparison between LC-DAD and APCI-MS/MS shows very good agreement for shrimp samples.

Nitrofuran antibiotics: a review on the application, prohibition and residual analysis

Nitrofuran antibiotics, employed for the treatment of bacterial diseases in livestock production, were banned from use in the European Union (EU) in 1995 due to concerns about the carcinogenicity of their residues in edible tissue. This review provides an overview of nitrofuran toxicity, metabolism, and also specific aspects of legislation surrounding their prohibition. Special attention is devoted to semicarbazide – a nitrofuran metabolite and food contaminant. Analytical procedures for nitrofuran analysis in various matrices and validation requirements for screening and confirmation methods with respect to EU regulations are also reviewed.

Determination of nitrofuran metabolites in milk by liquid chromatography–electrospray ionization tandem mass spectrometry

An LC–ESI–MS–MS method for the analysis of metabolites of four nitrofurans (furazolidone, furaltadone, nitrofurazone and nitrofurantoin) in raw milk has been developed. The samples were achieved by hydrolysis of the protein-bound drug metabolites, derivatization with 2-nitrobenzaldehyd (2-NBA) and clean-up extraction liquid–liquid with ethyl acetate. LC separation was achieved by using a Phenomenex Luna C-18 column. The mass spectrometer operated in multiple reaction monitoring mode (MRM) with positive electro-spray interface (ESI). The method validation was done according to the criteria laid down in Commission Decision No. 2002/657 EC. The validation includes the determination of linearity, repeatability, within-laboratory reproducibility, accuracy, decision limit (CCα) and detection capability (CCβ). The calibration curves were linear, with typical ( R 2) values higher than 0.991. The coefficient of variation (CV, %) was lower than 9.3% and the accuracy (RE, %) ranged from −9.0% to 7.0%. CV within-laboratory reproducibility was lower than 13%. The limits of decision (CCα) and detection capability (CCβ) were 0.12–0.29 μg/kg and 0.15–0.37 μg/kg, thus below the minimum required performance limit (MRPL) set at 1 μg/kg by the UE. This validated method was successfully applied for the determination of nitrofuran metabolites in a large number of milk samples.

Matrix-comprehensive in-house validation and robustness check of a confirmatory method for the determination of four nitrofuran metabolites in poultry muscle and shrimp by LC–MS/MS

An already well-described method for the determination of nitrofuran metabolites 3-amino-5-methyl-morpholino-2-oxazolidinone (AMOZ), 3-amino-2-oxazolidinone (AOZ), semicarbazide (SEM) and 1-aminohydantoin (AHD) was adapted to the needs of our laboratory and checked for its robustness regarding sample conditions and the processing step. Using the same data, the method was validated and the measurement uncertainty was estimated. All criteria and requirements of Commission Decision 2002/657/EC were fulfilled. The CC α determined lies between 0.1 and 0.7 μg/kg, the CC β lies between 0.1 and 0.9 μg/kg, the measurement uncertainty was estimated as being between 7 and 17% taking into account matrix, time and sample preparation influences.

Preparation of monoclonal antibodies against a derivative of semicarbazide as a metabolic target of nitrofurazone

Monoclonal antibodies (McAb) were produced to detect semicarbazide (SEM), a metabolite as a marker residue of nitrofurazone in animal food production. A carboxyphenyl derivative (CPSEM) of SEM was synthesized following derivatisation with 4-carboxybenzaldehyde (CBA). CPSEM was purified by recrystallization and conjugated to bovine serum albumin (BSA) or ovalbumin (OVA) as immunogen or coating antigen, respectively. Hybridomas were obtained by fusing mouse myeloma cells SP2/0 with splenocytes from the mice immunized with CPSEM–BSA. Hybridomas 1F10 and 4F2 secreting antibodies against CPSEM were obtained and subcloned. Ascites of monoclonal antibodies were prepared by injecting 1 × 10 6 cells of hybridoma 1F10 into mice abdomen. McAb obtained from hybridoma 1F10 was highly specific for CPSEM and had no cross-reaction with various nitrofuran metabolites and a range of veterinary drugs. The sensitivity of the McAb to SEM was 0.01 ng mL −1 and the IC 50 value was 1.3 ng mL −1 (SEM in the form of CPSEM). McAb 1F10 is suitable to develop an immunoassay for SEM with sufficient sensitivity for monitoring nitrofurazone residues.

Chloramphenicol, European Legislation and Hormesis - Commentary

The detection of chloramphenicol (CAP)—a broad-spectrum antibiotic—in shrimp imported into Europe from Asian countries in 2002 was regarded as yet another food-scandal by governments, albeit hardly noticed by the media and the public. The European reaction was closing down of the borders for fish products and making laboratories work overtime to analyse numerous batches of imported goods. Some European countries went so far as to have antibiotic-containing food-products destroyed, as these goods were presented as detrimental to human health. Any presence of CAP in food, which can be detected by several analytical methods, was a violation of European law, deemed a human health threat and followed by an immediate regulatory sanction of zero-tolerance (Hanekamp et al. 2003). Because CAP is regarded as probably carcinogenic (2A) and could be weakly genotoxic, the zero-tolerance approach reflects the traditional use of the Linear Non-Threshold (LNT) model so deeply embedded in toxicological and regulatory thinking, especially concerning genotoxic carcinogens. This regulatory position and human health perspective, however, proved to be untenable in the case of CAP but also for other antibiotics not allowed in the food chain, such as nitrofurans. Because of blatant misuses, zero-tolerance had been deemed an opportune method to ban the use of certain veterinary products, residues of which may show up in foods. However, the unfeasibility of zero-tolerance came to the fore as a result of the analytical progress made in the last two decades of the twentieth century. CAP (and also nitrofurans) proved to be more ubiquitous in food—albeit at extremely low levels—than mere abuse probably could account for (Hanekamp et al. 2003). However, one of the present authors (JCH) recognized that zero-tolerance and the LNT model (IPCS-INCHEM 2006) are regulatory conveniences infused with a precautionary human health perspective. Moreover, it was clear that medicinal products such as CAP are rarely in use as human medicine and are banned for veterinary use not because of inherent risks at low-level exposures, but because JECFA (Joint Expert Committee on Food Additives, FAO) could not establish an ADI for lack of scientific data (IPCS-INCHEM 2006). In Europe this was expediently translated as ‘dangerous at any dose’ and officially regarded as such. Confronted with such intransigence, Hanekamp embraced the case for hormesis presented by Calabrese in numerous papers (Calabrese et al. 1999; Calabrese and Baldwin 2001a; Calabrese and Baldwin 2001b; Calabrese and Baldwin 1997; Calabrese and Baldwin 2003a; Calabrese and Baldwin 2003b), as a means to advance a rational approach of low-level exposures of chemicals in food, which need not be zero according to hormesis (Hanekamp and Kwakman 2004). In doing so, the concept of a Toxicological Insignificant Exposure level (TIE) (Kroes et al. 2004) was introduced, whereby the hormetic part of the dose-response curve was ‘translated’ into a toxicological threshold. We then evaluated the TIE within the framework of hormesis, where insignificance was understood not as a regulatory evaluation based on a MTR (Maximum Tolerable Risk) level of say 1:1,000,000, as is done within the threshold of toxicological concern (TTC) concept, but as a direct toxicological dose response bioassay and assessment (Calabrese and Cook 2005). As a result, a regulatory shift away from zero tolerance came to be when the European Commission published a decision on 11 January 2005 (Commission Decision 2005), according to which CAP no longer is regulated at zero level but at the MRPL (Minimum Required Performance Limit) level. For CAP the MRPL is set at 0.3 ppb (for nitrofuran metabolites the MRPLs are set at 1 ppb). Prior to this decision, MRPLs were whatever low concentration levels that regulatory laboratories in the European Community could detect and confirm. With this decision MRPLs have now been given legal status in terms of explicit levels of concern. The CAP case here described is the first policy example in which a regulatory shift is observed from zero tolerance to a threshold approach on the basis of hormetic considerations, which it is hoped could pave the way for incorporation of the hormetic perspective into not only food safety regulation but also into environmental regulation. In our view, this is clearly needed to improve pharmaceutical and industrial chemical regulation (European Commission 2004), especially in light of the recent EC decision (Commission Decision 2005) and the overwhelming evidence of hormesis in relation to many low-level exposures (Calabrese and Baldwin 2001a; Calabrese and Baldwin 2003a; Hanekamp and Wijnands 2004; Wiener 2001).

Multi-residue monitoring for the simultaneous determination of five nitrofurans (furazolidone, furaltadone, nitrofurazone, nitrofurantoine, nifursol) in poultry muscle tissue through the detection of their five major metabolites (AOZ, AMOZ, SEM, AHD, DNSAH) by liquid chromatography coupled to electrospray tandem mass spectrometry—In-house validation in line with Commission Decision 657/2002/EC

Following the ban of four nitrofurans in the mid-90s (furazolidone, furaltadone, nitrofurantoine, nitrofurazone), the nifursol, a veterinary drug from the nitrofuran class of antibacterials which has been used prophylactically as feed additive for treating turkeys against histomoniasis (blackhead disease) was also declared in Annex IV of the European Union Directive no. 90/2377/EC in 2002 according to the Regulation no. 1756/2002/EC. As for the four other nitrofurans, nifursol disappears from tissues within a few days after treatment of food-producing animals. But toxic metabolites are still present for longer periods (several weeks or even months). The major metabolite that can readily be monitored in the tissues following nifursol abuse is the 3,5-dinitro-salicylic acid hydrazine (DNSAH). This article displays some improvements and the revalidation of the analytical method by liquid chromatography coupled to electrospray tandem mass spectrometry (LC-esiMS/MS) already in use in our laboratory for monitoring nitrofuran metabolites but also including the nifursol metabolite at the confirmatory minimum required performance level (MRPL) of 1μgkg−1. The validation is applied both to artificially and to naturally incurred turkey muscle.

Determination of nitrofurans in animal feeds by liquid chromatography-UV photodiode array detection and liquid chromatography-ionspray tandem mass spectrometry

Within the EU, the use of nitrofurans is prohibited in food production animals. For this reason detection of these compounds in feedingstuffs, at whatever limit, constitutes an offence under EU legislation. This detection generally involves the use of analytical methods with limits of quantification lowers than 1mgkg−1. These procedures are unsuitable for the detection and confirmation of trace amounts of nitrofurans in feedingstuffs due to contamination. It is well known that very low concentrations of these compounds can be the source of residues of nitrofuran metabolites in meat and other edible products obtained from animals consuming the contaminated feed. The present multi-compound method was capable of measuring very low concentrations of nitrofurantoin (NFT), nitrofurazone (NFZ), furazolidone (FZD) and furaltadone (FTD) in animal feed using nifuroxazide (NXZ) as internal standard. Following ethyl acetate extraction at mild alkaline conditions and purification on NH2 column, the nitrofurans are determined using liquid chromatography with photodiode-array detection (LC-DAD). It was observed a CCα ranged from 50 to 100μgkg−1. The liquid chromatography-tandem mass spectrometric (LC-MS/MS) procedure was used to confirm the identity of the suspected presence of any of the nitrofuran compounds.

Validation of a confirmatory method for the determination of residues of four nitrofurans in egg by liquid chromatography–tandem mass spectrometry with the software InterVal

A method for the detection and determination of nitrofuran derivatives in egg by liquid chromatography–tandem mass spectrometry (LC–MS/MS) was validated with the software InterVal and can be applied for the confirmation of nitrofuran metabolites in fresh or lyophilised eggs. The validation study comprises variations in operator, storage condition, breeding, equipment and duration of sample preparation. A comprehensive overview of the robustness of the method is obtained by analysing eight samples at six concentration levels. First results of short- and medium-term investigations for stability of analytes in solution show that standard solutions of nitrofuran metabolites are stable for at least 1 year when stored at +4°C in the dark. The decision limit CCα expressed for the underivatised metabolite is 0.05μgkg−1 for 3-amino-5-methyl-morpholino-2-oxazolidinone, 0.03μgkg−1 for 3-amino-2-oxazolidinone, 0.20μgkg−1 for semicarbazide and 0.22μgkg−1 for 1-amino-hydantoin.

Advantages of LC–MS–MS compared to LC–MS for the determination of nitrofuran residues in honey

In the framework of developing analyses for exogenous contaminants in food matrices such as honey, we have compared data obtained by high-performance liquid chromatography coupled with mass spectrometry (LC-MS) to those provided by high-performance liquid chromatography and tandem mass spectrometry (LC-MS-MS). Initial results obtained with LC-MS showed that the technique lacked selectivity, which is why the method was validated by LC-MS-MS. This method involves a solid-phase extraction (SPE) of nitrofuran metabolites and nitrofuran parent drugs, a derivatization by 2-nitrobenzaldehyde for 17 h, and finally a clean-up by SPE. The data obtained show that the limits of detection varied between 0.2 and 0.6 microg kg(-1) for the metabolites and between 1 and 2 microg kg(-1) for nitrofuran parent drugs. The method was applied to different flower honeys. The results showed that nitrofurans (used as antibiotics) are consistently present in this matrix, the predominant compound being furazolidone. Figure Working bees.

Simultaneous separation of nitrofuran antibiotics and their metabolites by using micellar electrokinetic capillary chromatography

Mixtures comprising nitrofuran antibiotics (NFA) and nitrofuran metabolites (NFM) were resolved for the first time by using MEKC. Sodium deoxycholate (SDC) was chosen as the micelle-forming surfactant. Optimization of separation conditions was achieved by using a central composite experimental design (CCD) approach. Experimental parameters such as concentration ratio of borate to phosphate in the buffer, pH of the running electrolyte and voltage were investigated. The effect of concentration of the surfactant on resolution was significant. Under optimal conditions of 80 mM SDC, pH 9.0, (20 mM borate + 20 mM phosphate) and 16 kV, the resolution between eight consecutive peak pairs ranged from 1.9 to 11.8. Due to the absence of a UV-active chromophore in the metabolites, they were derivatized with 2-nitrobenzaldehyde (2-NBA). In order to mimic a proposed extraction procedure for the analysis of both NFA and/or derivatized NFM in a sample, aqueous samples (prederivatized with 2-NBA) were extracted by using C(18) SPE cartridges. After washing with H(2)O, the cartridges were eluted with a small portion of organic solvent with weak elution characteristics to remove excess 2-NBA (hexane was chosen). Target analytes were then recovered with ACN. Excellent reproducibility of migration time (t(mig)) was achieved for all analytes using the developed MECC approach, with absolute t(mig) <1% RSD and t(mig) ratio <0.2% RSD, and peak area ratio was 4% RSD. The LOD for each compound, calculated by extrapolating to an S/N of 3, were found to be 0.19-2.0 microg/mL.

Proficiency study for the determination of nitrofuran metabolites in shrimps

A proficiency test for the determination of nitrofuran metabolites in shrimp tissue was organized in the first half of 2003. This test was intended to allow the participants to use their routine method and to assess their competence on this specific analysis. The participation in this proficiency test was offered to all the National Reference Laboratories (NRLs) of the European Union (EU) in charge of the analysis of nitrofurans, to Official Laboratories of the then 10 Candidate Countries for entry in EU and to some countries exporting food to the EU. The participants (20) analysed nitrofuran metabolites in eight randomly coded frozen samples including three blank samples. All participants performed a confirmatory method using liquid chromatography/mass spectrometry to detect total nitrofuran metabolite residues. Both qualitative and quantitative analyses of the results were investigated. Qualitatively, 16 laboratories out of 20 gave the correct interpretation of the results in term of compliant/non-compliant sample. Quantitatively, laboratory performance was evaluated by calculating the z-scores.

Evaluation of the limit of performance of an analytical method based on a statistical calculation of its critical concentrations according to ISO standard 11843: Application to routine control of banned veterinary drug residues in food according to European Decision 657/2002/EC

Traceability of the measurement of analytical parameters capable of evaluating the performance of methods is an important concept for the assessment of quality for the routine control, especially for residue monitoring of non-authorized medicinal substances in food from animal origin. The European Decision no. 657/2002/EC recommends to calculate two statistical limits, CCα and CCβ, which allow to evaluate the critical concentrations above which the method reliably distinguish and quantify a substance taking into account the variability of the method and the statistical risk to take a wrong decision. The calculation, which can be derived from the ISO standard no. 11843 is applied on a routine basis. An example displays a very simple way for evaluating the performance of an LC-MSMS method which has been validated a few years ago and is qualified onto a Micromass Quattro LCZ tandem mass spectrometer to monitor and confirm the nitrofuran metabolite residues in food from animal origin.

Determination of nitrofuran metabolites in poultry muscle and eggs by liquid chromatography-tandem mass spectrometry

The use of nitrofurans in food-producing animals has been banned in EU. Detection of the protein-bound nitrofuran metabolites is the best approach to evaluate their utilization. A fast, sensitive and reliable LC–MS–MS method is presented to analyze simultaneously the metabolites of four commonly used nitrofuran drugs, furazolidone, furaltadone, nitrofurazone and nitrofurantoin. The sample clean up was performed by a single liquid–liquid extraction step, after a hydrolysis and derivatisation process. Separation of the molecules was performed by liquid chromatography in a C18 column (100 mm × 2.1 mm, 4 μm) at room temperature. The quantitative and confirmatory determination of these metabolites was performed by multiple reactions monitoring (MRM). Limits of quantification of 0.5 ng g −1 were achieved and the total analysis was accomplished in 5 min. This protocol has been applied to identify contaminated samples of poultry muscle and egg products.

Transfer of nitrofuran residues from parent broiler breeder chickens to broiler progeny

1. The use of nitrofuran antibiotics in food-producing animals is prohibited within the EU. Countries in the EU, as well those intending to export food to the EU, must ensure that their products are free from nitrofuran residues. 2. As a result of recent global problems where chicken meat from a wide range of countries has been contaminated with nitrofuran metabolites, an investigation was performed to discover whether or not residues of the nitrofurans might be transferred from parent breeder chickens to their offspring broilers. 3. Four groups of broiler breeders were each treated with one of the nitrofurans: furazolidone, nitrofurazone, nitrofurantoin or furaltadone. Residues of their side-chain metabolites, AOZ, SEM, AHD and AMOZ, were detected in the fertilised eggs at concentrations up to 1567 µg/kg. 4. However, in the chicks that subsequently hatched from these eggs, residue concentrations of SEM, for example, were only found up to 26·6 and 32·5 µg/kg in liver and muscle, respectively, for 1-d-old chicks. Residue concentrations in tissues had fallen below the detection limit of the analytical method for 40-d-old broiler chicks, for all compounds except for semicarbazide (SEM, the nitrofurazone metabolite). 5. Relatively high concentrations of nitrofurans are available to the newly hatched chick through the egg yolk. However, most of these residues are neither utilised nor deposited in the liver or muscle.

The occurrence of nitrofuran metabolites in the tissues of chickens exposed to very low dietary concentrations of the nitrofurans

The global problem of food products contaminated by residues of the banned carcinogenic nitrofuran drugs has prompted research into how such residues accumulate in tissues. In the study described here, two aspects have been investigated where the nitrofurans accumulate in tissues from chickens exposed to either a dietary or an environmental source of contamination. Twenty groups of broilers were fed a diet containing one of the nitrofurans: furazolidone, nitrofurazone, nitrofurantoin or furaltadone at concentrations of 30, 100, 300, 1000 and 3000 µg kg−1. At the lowest concentration of furazolidone contamination (0.01% of the therapeutic dose) tissue bound AOZ metabolite residues were detected in liver (1.1 ± 0.2 µg kg−1) and in muscle (0.33 ± 0.03 µg kg−1). Similar results were obtained for AMOZ (0.6 ± 0.2 µg kg−1 in liver), the tissue bound metabolite of furaltadone. There was no appreciable accumulation of nitrofurantoin in chicken muscle. The AHD metabolite was not detected in muscle from birds fed nitrofurantoin at either 30 or 100 µg kg−1. For nitrofurazone the concentrations of the SEM metabolite were higher in muscle than in liver for all dietary concentrations. The potential for a contaminated environment to cause nitrofuran residues in chickens was investigated. Six chickens were placed in a pen that was previously occupied by birds fed a diet containing 3000 µg kg−1 of furazolidone. After 24 hours’ exposure of the chickens to the litter in the pen, AOZ residues of 0.13 ± 0.04 and 0.10 ± 0.03 µg kg−1 were detected in liver and muscle, respectively. The results of both experiments have implications for the poultry industry in trying to eliminate nitrofurans from their production systems, and for regulatory analysts faced with the detection of low concentrations of the drugs, both in tissues and in feedingstuffs.