Silver nanopopcorns decorated on flexible membrane for SERS detection of nitrofurazone.

The synthesis of three-dimensional silver nanopopcorns (Ag NPCs) onto a flexible polycarbonate membrane (PCM) for the detection of nitrofurazone (NFZ) on the fish surface by surface-enhanced Raman spectroscopy (SERS) is presented. The proposed flexible Ag-NPCs/PCM SERS substrate exhibits significant Raman signal intensity enhancement with the measured enhancement factor of 2.36 × 106. This is primarily attributed to the hotspots created on Ag NPCs, including numerous nanoscale protrusions and internal crevices distributed across the surface of Ag NPCs. The detection of NFZ by this flexible SERS substrate demonstrates a low limit of detection (LOD) of 3.7 × 10-9 M and uniform and reproducible Raman signal intensities with a relative standard deviation below 8.34%. It also exhibits excellent stability, retaining 70% of its efficacy even after 10 days of storage. Notably, the practical detection of NFZ in tap water, honey water, and fish surfaces achieves LOD values of 1.35 × 10-8 M, 5.76 × 10-7 M, and 3.61 × 10-8 M, respectively,  which highlights its effectiveness across different sample types. The developed Ag-NPCs/PCM SERS substrate presents promising potential for sensitive SERS detection of toxic substances in real-world samples.

Synthesis and spectroscopic characterization of 13 C4 -labeled 4-cyano-2-oxobutyraldehyde semicarbazone: A metabolite of nitrofurazone.

Nitrofurazone usage in food-producing animals is prohibited in most countries, including the United States. Regulatory agencies regularly monitor its use in domestic, export/import animals' food products by measuring the semicarbazide (SEM) metabolite as a biomarker of nitrofurazone exposure. However, the use of SEM is controversial because it is also produced in food naturally and thus gives false positive results. A cyano-metabolite, 4-cyano-2-oxobutyraldehyde semicarbazone (COBS), is proposed as an alternate specific marker of nitrofurazone to distinguish nitrofurazone from treated or untreated animals. A synthetic method was developed to produce COBS via metallic hydrogenation of nitrofurazone. The product was isolated and characterized by one- and two-dimensional nuclear magnetic spectroscopy (NMR) experiments, Fourier-transform infrared spectroscopy (FT-IR), and mass spectrometry. The developed synthetic procedure was further extended to synthesize isotopically labeled 4-[13 C]-cyano-2-oxo- [2, 3, 4-13 C3 ]-butyraldehyde semicarbazone. Labeled COBS is useful as an internal standard for its quantification in food-producing animals. Thus, the developed method provides a possibility for its commercial synthesis to procure COBS. This is the first synthesis of the alternate specific marker metabolite of nitrofurazone for possible usage in regulatory analysis to solve a real-world problem.

Furazolidone and Nitrofurazone Metabolic Studies in Crucian Carp by Ultra-Performance Liquid Chromatography Tandem Mass Spectrometry.

In this work, the detection of the furazolidone (FZD) and nitrofurazone (NFZ) metabolites residuals in crucian carp are focused. Crucian carps of identical size were exposed to the mixed nitrofuran antibiotics under optimized bath conditions at a concentration of 50 mg/L, 26 ± 0.5°C for 24 h. Then, liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-MSMS) was performed after the drug exposure experiments when the nitrofuran metabolites were enriched in organisms. During the period of 0-144 h, residue levels of the 3-amino-2-oxazolidinone (AOZ) gradually decreased with a prolonged sampling time. The changing trend in semicarbazide (SEM) with the sample collection duration is divided into two stages, and its concentration showed a trend of rising first and then falling. The metabolite concentration-time curve demonstrates that 24 h was used as a sampling time, and fish muscle was selected as tissue samples in the further quantitative study. A novel crucian carp-enrichment procedure coupled to LC-ESI-MSMS quantitative method was further explored based on much metabolite data. According to the exponential curve of the SEM-to-AOZ concentration ratio at a precisely designed FZD-to-NFZ mass ratio, the final FZD content of the veterinary NFZ antibiotics was 0.069 ± 0.005% (in terms of mass).

Synthesis and Characterization of Pyrochlore-Type Praseodymium Stannate Nanoparticles: An Effective Electrocatalyst for Detection of Nitrofurazone Drug in Biological Samples.

Apart from perovskites, the development of different types of pyrochlore oxides is highly focused on various electrochemical applications in recent times. Based on this, we have synthesized pyrochlore-type praseodymium stannate nanoparticles (Pr2Sn2O7 NPs) by using a coprecipitation method and further investigated by different analytical and spectroscopic techniques such as X-ray diffraction, Raman spectroscopy, field emission-scanning electron microscopy, high resolution-transmission electron microscopy, and X-ray photoelectron spectroscopy analysis. Followed by this, we have designed a unique and novel electrochemical sensor for nitrofurazone detection, by modifying the glassy carbon electrode (GCE) with the prepared Pr2Sn2O7 NPs. For that, the electrochemical experiments were performed by using cyclic voltammetry and differential pulse voltammetry techniques. The Pr2Sn2O7 NPs modified GCE exhibits high sensitivity (2.11 µA µM-1 cm-2), selectivity, dynamic linear ranges (0.01-24 µM and 32-332 µM), and lower detection limit (4 nM). Furthermore, the Pr2Sn2O7 NPs demonstrated promising real sample analysis with good recovery results in biological samples (human urine and blood serum) which showed better results than the noble metal catalysts. Based on these results, the present work gives clear evidence that the pyrochlore oxides are highly suitable electrode materials for performing outstanding catalytic activity toward electrochemical sensors.

Improving sensitivity of antimicrobial drug nitrofurazone detection in food and biological samples based on nanostructured anatase-titania sheathed reduced graphene oxide.

In this study, we have prepared anatase titanium (IV) oxide warped reduced graphene oxide nanocomposites (TiO2-rGO NC) using ultrasonic methodology. The morphology of the TiO2-rGO NC was studied using FESEM and TEM. In addition, XRD, Raman, thermogravimetric analysis (TGA) and XPS are used to analyze the crystallinity and chemical composition of the TiO2-rGO NC. We have also investigated the electrochemical behavior of the as-prepared NCs with electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and different pulse voltammetry techniques (DPV). The TiO2-rGO NC modified electrode shows the lower charge transfer resistance (R ct ) of 62.87 Ω. Next, the glassy carbon electrode (GCE) was modified with sonochemically prepared TiO2-rGO NC and used to determine the electrocatalytic reduction of nitrofurazone (NTF). Thus, the proposed sensor established the wider covering range (WCR) of 0.01 to 380 µM and an excellent detection limit of 2.28 nM. Finally, the TiO2-rGO NC/GCE was applied to determine the NTF in real samples, including crayfish and human blood serum samples, which acquired good found and recovery values.

Investigating the Suitability of Semicarbazide as an Indicator of Preharvest Nitrofurazone Use in Raw Chicken.

ABSTRACT: Semicarbazide (SEM) is the U.S. Food and Drug Administration's official marker for nitrofurazone use in food animals. The U.S. Department of Agriculture Food Safety and Inspection Service conducted a study to evaluate the source of SEM that was identified by a U.S. trading partner in a subset of chicken samples presented for inspection, even though nitrofurazone has been banned from use in U.S. food-producing animals since 2002. The study design included analyses to detect and quantify total and bound SEM in chicken collected from the eight U.S. establishments that were associated with the reported detection of SEM. Samples were collected immediately following evisceration, chilling, and cutting carcass into parts (cut-up). Although antimicrobial interventions (processes to reduce pathogen concentrations) are typically used at all three of these processing steps, the product contact time during chilling is significantly longer (hours versus seconds) than during evisceration and cut-up. In addition, parts were analyzed after 0, 10, 20, and 30 days of frozen storage. No postevisceration samples tested positive for SEM; however, most samples collected postchilling and after cut-up tested positive. The absence of SEM in postevisceration samples and detection in the subsequent postchilling samples and after the cut-up samples suggest that the detection of SEM in the sampled products is not indicative of preharvest nitrofurazone use and may be a result of postharvest processing in these establishments.

A Water-Stable Lanthanide Coordination Polymer as Multicenter Platform for Ratiometric Luminescent Sensing Antibiotics.

As a hot topic of global concern, the distinguishing and detecting of antibiotic pollution is crucial owing to its adverse effect on ecosystems and human health stemming from excessive use and poor management. Herein, a water-stable lanthanide coordination polymer sensor (Dy-TCPB) with multiple emitting centers is prepared. The versatile Dy-TCPB can conveniently differentiate various antibiotics, and displays a self-calibration luminescent response to nitrofurazone (NFZ) and furazolidone (FZD). Each antibiotic exhibits notable correlation to a unique combination of the two ligand-to-Dy ion emission intensity ratios, enabling two-dimensional fingerprint recognition. Furthermore, the novel self-calibration sensor demonstrates effective recognition of NFZ and FZD with excellent sensitivity and selectivity, and detection limits as low as 0.0476 and 0.0482 µm for NFZ and FZD, respectively. The synthetic approach for the fabrication of a singular coordination polymer exhibiting multiple emissions provides a promising strategy for the development of facile and effective ratiometric sensors.

Guest-Induced Ultrasensitive Detection of Multiple Toxic Organics and Fe3+ Ions in a Strategically Designed and Regenerative Smart Fluorescent Metal-Organic Framework.

Luminescent metal-organic frameworks (LMOFs) are promising functional materials for sustainable applications, where an analyte-induced multiresponsive system with good recyclability is beneficial for detecting numerous lethal pollutants. We designed and built the dual-functionalized, three-dimensional Zn(II)-framework [Zn3( bpg)1.5( azdc)3]·(DMF)5.9·(H2O)1.05 (CSMCRI-1) using an -OH group-integrated bpg linker and a -N═N- moiety containing H2 azdc ligand, which functions as a unique tetrasensoric fluorescent probe. The activated CSMCRI-1 (1') represents the hitherto unreported pillar-layer framework for extremely selective fluorescence quenching by nitrofurazone antibiotics as well as explosive nitro-aromatic 2,4,6-trinitrophenol, where ultrasensitive detection is achieved for both the electron-lacking analytes. Impressively, 1' represents the first ever MOF for significant fluorescence "turn-on" detection of toxic and electron-rich 4-aminophenol in the concurrent presence of isomeric analogues. Density functional theory calculations highlight the specific importance of pillar functionalization in the "turn-on" or "turn-off" responses of 1' by electronically divergent toxic organics and provide further proof of supramolecular interactions between the framework and analytes. The fluorescence intensity of 1' dramatically quenches by a trace amount of Fe3+ ions over other competing metal ions, alongside visible colorimetric change of the framework in solid and solution phase upon Fe3+ encapsulation. The sensing ability of 1' remains unaltered for multiple cycles toward all lethal pollutants. The sensing mechanism is attributed to both dynamic and static quenching as well as resonance energy transfer, which strongly comply with the predictions of theoretical simulations. Considering the long-term and real-time monitoring, AND as well as OR molecular logic gates are constructed based on the discriminative fluorescence response for each analyte that provides a platform to fabricate smart LMOFs with multimode logic operations.

High reliable and robust ultrathin-layer gold coating porous silver substrate via galvanic-free deposition for solid phase microextraction coupled with surface enhanced Raman spectroscopy.

That intense demand for both high sensitivity and high reliability has been a key factor strengthening the surface enhanced Raman spectroscopy (SERS) in the analytical application, particular in the hyphenation with pre-concentration technique. Credible data acquisition and processing is very dependent on the stable and uniform performance of SERS-active substrate. Here, a reliable and uniform ultrathin-layer Au was proposed for protecting the porous Ag fiber (porous Ag@Au) and applied in the solid phase microextraction coupled with SERS. The Au layer was carefully deposited on porous Ag surface to form the uniform film by a galvanic-free displacement reaction. This coating endowed the substrate with high oxidation-resistance under heating and good durability in the atmosphere condition. The extraction and SERS performance of Nitrofurazone and Semicarbazide were investigated on this fiber, the bands at 1350 cm-1 and 1387 cm-1 were selected as the characteristic peaks for quantitative determination, respectively. This robust and sensitive substrate provide the high enhancement factor of 1.3 × 106 and low LOD of 5.1 ppb for the extraction and identification of Nitrofurazone compounds. Importantly, this work develops a versatile strategy for rapid detection of prohibited antibiotic and its marker residue in a complex matrix.

Nitrofurazone quantification in milk at the European Union minimum required performance limit of 1 ng g(-1): circumventing the semicarbazide problem.

Nitrofurazone is an antibiotic with carcinogenic properties. Efforts by regulatory authorities to control nitrofurazone from agricultural foods are an important public health measure that have, to some extent, been undermined by widespread use amongst laboratories of the unreliable marker metabolite semicarbazide. This work confirms what has long been suspected, namely that powdered dairy products that are initially free of semicarbazide develop semicarbazide under storage conditions such as occur normally across commercial supply chains. The low ng g(-)(1) levels of semicarbazide formed in this way are insufficient to present any food safety hazard. That such development of a marker metabolite is demonstrated to occur by innocent means effectively invalidates the use of semicarbazide as a marker metabolite for powdered dairy products, and exacerbates the regulatory need for a more suitable analytical methodology. In milk, unlike meat, nitrofurazone is known to remain stable and thus available for analysis in the intact form, rather than necessitating any use of a metabolite or fragment. However, no previous methodology that was capable of achieving the stringent European minimum required performance limit of 1 ng g(-)(1) when using intact nitrofurazone had been described for milk. This work describes a specific methodology using LC-MS/MS for milk and milk powder; it achieves detection of intact nitrofurazone (as well as furazolidone, furaltadone and nitrofurantoin) to levels well below 1 ng g(-)(1). Laboratories will no longer need to use semicarbazide as an unreliable marker metabolite for the analysis of nitrofurazone in dairy products, paving the way for regulatory authorities to better control nitrofurazone abuse with greater confidence.

Semicarbazide - from state-of-the-art analytical methods and exposure to toxicity: a review.

This review assesses the state of the art concerning semicarbazide (SEM). Originally, SEM was primarily detected as a nitrofurazone veterinary metabolite, but over time scientists gradually found that azodicarbonamide in sealed cans and flour could also lead to the generation of SEM. This discovery makes the study of SEM particularly interesting. At present, an increasing number of researchers are investigating the toxicity of SEM and developing more and better analytical methods for the determination of SEM. In recent years, many researchers have focused on exposure from different foods, the public awareness of hazards and analytical detection methods for SEM in different foods. Although there have been significant achievements, these results have not been summarised in a review. The exposure from different foods, toxicity and methods of detection for SEM are comprehensively reviewed here. This review will provide not only others with a better understanding of SEM but also background information to facilitate future research.

HPLC-DAD stability indicating determination of nitrofurazone and lidocaine hydrochloride in their combined topical dosage form.

In this work, a simple, rapid, and selective high-performance liquid chromatography (HPLC) method with diode array detection was developed for the simultaneous determination of nitrofurazone (NZ) and lidocaine hydrochloride (LD). The chromatographic separation was achieved by using Zorbax Eclipse XDB-C(18) (4.6 x 150 mm, 5 mum p.s.) analytical column and a mobile phase composed of 0.025 M disodium hydrogen phosphate-methanol-triethylamine (70:30:0.1, v/v/v) (pH 4.0) at a flow rate of 1 mL/min. The detector was set at wavelengths 374 and 220 nm for NZ and LD, respectively, and quantification of the analytes was based on measuring their peak areas. The retention times for NZ and LD were approximately 4.5 and 5.7 min, respectively. The reliability and analytical performance of the proposed HPLC procedure were statistically validated with respect to system suitability, linearity, ranges, precision, accuracy, selectivity, robustness, and detection and quantification limits. The linear dynamic ranges were 0.5-25 and 2.5-100 mug/mL for NZ and LD, respectively, with correlation coefficients > 0.999. The stability-indicating aspects of the proposed method were demonstrated by the resolution of the two analytes from the related substance and potential impurity (2,6-dimethylaniline) as well as from forced-degradation products. The validated HPLC method was successfully extended to the analysis of the combined topical dosage form (soluble dressing) where no interfering peaks were encountered from the dosage form matrix or the inactive ingredients.

Cyano metabolite as a biomarker of nitrofurazone in channel catfish.

The use of nitrofuran drugs in food-producing animals continues to attract international concern as a food safety issue. Methods for monitoring nitrofuran residues have been directed to the intact side chain of tissue-bound metabolites. Semicarbazide, the side chain of nitrofurazone (NFZ), can enter food products from non-NFZ sources, suggesting the need for an alternative biomarker for confirmatory purposes. We characterized a cyano derivative as a major metabolite of NFZ in channel catfish (Ictalurus punctatus). The depletion of cyano metabolite was examined in the muscle of channel catfish after oral dosing (10 mg of NFZ/kg of body weight). Parent NFZ was rapidly eliminated in muscle, with a half-life of 6.3 h. The cyano metabolite was detected for up to 2 weeks, with an elimination half-life of 81 h. The cyano metabolite represents an alternative biomarker for confirming the use of NFZ in channel catfish.

[Determination of nitrofurazone in livestock products and seafoods by liquid chromatography-tandem mass spectrometry].

A sensitive and selective method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the determination of nitrofurazone (NFZ) in swine muscle, swine liver, chicken muscle, chicken liver, egg, eel, yellowtail and shrimp has been developed. The drug was extracted with 0.2% metaphosphoric acid-methanol (6 : 4), and the extracts were cleaned up on an Oasis HLB cartridge (200 mg). The extracts were analyzed by LC-MS/MS using electrospray ionizationin the negative ion mode. The LC separation was performed on a Hypersil Gold C18 column (15 cmx2.1 mm i.d.) with a gradient system of 0.01% formic acid-acetonitrile as the mobile phase at a flow rate of 0.2 mL/min. The quantitative and confirmatory determination of NFZ was performed by selected reaction monitoring (SRM). The calibration graph for NFZ was rectilinear from 0.2 to 100 ng/mL with SRM. The recoveries of NFZ from samples fortified at 1 and 10 ng/g were 79.6-106.8%, and quantification limit was 0.2 ng/g for the drug. This is well below the detection limit (1 ng/g) set by the Japanese Food Sanitation Law.

Interaction between nitroheterocyclic compounds with beta-cyclodextrins: phase solubility and HPLC studies.

Chagas disease is a serious health problem for Latin America. Nitrofurazone (NF) and Hidroxymethylnitrofurazone (NFOH) are active against Trypanosoma cruzi. The effect of beta-cyclodextrin (beta-CD) and dimethyl-beta-cyclodextrin (DM-beta-CD) complexation on the UV absorption and retention time of nitrofurazone (NF) and its hydroxymethylated analog (NFOH) were studied in solution. The retention behavior was analyzed on a reversed phase C18 column and the mobile phase used was acetonitrile-water (20/80 v/v), in which cyclodextrins (beta-CD or DM-beta-CD) were incorporated as a mobile phase additive. The decrease in the retention times of NF (or NFOH) with increasing concentration of HP-beta-CD enables the determination of the complex stability constants by HPLC. A phase-solubility study was performed, according to the method reported by Higuchi and Connors, to evaluate the changes of NF/NFOH in the complexation state, and the diagrams obtained suggested that it forms complexes with a stoichiometry of 1:1. This is an important study for the characterization of potential formulations to be used as therapeutic options for the treatment of Chagas disease.

A simple and sensitive spectrofluorimetric method for analysis of some nitrofuran drugs in pharmaceutical preparations.

A simple, rapid, selective and sensitive spectrofluorimetric method was described for the analysis of three nitrofuran drugs, namely, nifuroxazide (NX), nitrofurantoin (NT) and nitrofurazone (NZ). The method involved the alkaline hydrolysis of the studied drugs by warming with 0.1 M sodium hydroxide solution then dilution with distilled water for NX or 2-propanol for NT and NZ. The formed fluorophores were measured at 465 nm (lambda (Ex) 265 nm), 458 nm (lambda (Ex) 245 nm) and 445 nm (lambda (Ex) 245 nm) for NX, NT and NZ, respectively. The reaction pathway was discussed and the structures of the fluorescent products were proposed. The different experimental parameters were studied and optimized. Regression analysis showed good correlation between fluorescence intensity and concentration over the ranges 0.08-1.00, 0.02-0.24 and 0.004-0.050 microg ml(-1) for NX, NT and NZ, respectively. The limits of detection of the method were 8.0, 1.9 and 0.3 ng ml(-1) for NX, NT and NZ, respectively. The proposed method was validated in terms of accuracy, precision and specificity, and it was successfully applied for the assay of the three nitrofurans in their different dosage forms. No interference was observed from common pharmaceutical adjuvants. The results were favorably compared with those obtained by reference spectrophotometric methods.

The identification of potential alternative biomarkers of nitrofurazone abuse in animal derived food products.

Semicarbazide (SEM) was considered to be a characteristic protein-bound side-chain metabolite of the banned veterinary drug nitrofurazone and used as a marker of nitrofurazone abuse. It was recently discovered that SEM can arise in food from sources other than nitrofurazone. This uncertainty over the source of SEM may be overcome if alternative markers specific to tissue-bound nitrofurazone residues can be determined. The structure of nitrofurazone metabolites in vivo and particular proteins to which they are bound are not known. These proteins with altered structure due to the presence of the drug metabolites can be considered as potential alternative biomarkers of nitrofurazone abuse. The proteins implicated in the in vivo binding of nitrofurazone were separated and identified. A crude mixture of proteins extracted from the liver of a rat treated with the drug was separated using a series of different techniques such as preparative isoelectric focusing and size exclusion HPLC. Multiple fractions were assayed by LC-MS/MS to detect the presence of SEM. The proteins containing SEM residues were identified by peptide mass mapping using trypsin digestion and MALDI-TOF. The first protein identified as containing high concentration of SEM was albumin. It was also shown that low molecular weight species within a protein mixture whose main constituent was glutathione S-transferase contained a high concentration of SEM. The chemical composition of these components is under investigation. Preliminary data suggest the SEM forms part of a nitrofurazone metabolite conjugated to glutathione.

Flow injection chemiluminescence determination of nitrofurazone in pharmaceutical preparations and biological fluids based on oxidation by singlet oxygen generated in N-bromosuccinimide-hydrogen peroxide reaction.

A simple flow injection chemiluminescence (FI-CL) method was proposed for the determination of nitrofurazone. Strong CL signal was generated during the reaction of nitrofurazone with H(2)O(2) and N-bromosuccinimide (NBS) in alkaline condition. The CL signal was proportional to the nitrofurazone concentration in the range 1.0 x 10(-7) to 1.0 x 10(-5) g mL(-1). The detection limit was 2 x 10(-8) g mL(-1) nitrofurazone and the relative standard deviation was less than 4% (6.0 x 10(-6) g mL(-1) nitrofurazone, n=11). The proposed method was successfully applied to the determination of nitrofurazone in compound furacillin nasal drops, human plasma and urine samples. The CL reaction mechanism was also discussed briefly. Singlet oxygen generated in the reaction between H(2)O(2) and NBS was suggested to be participated in the CL reaction.

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 1 mg kg(-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 CCalpha ranged from 50 to 100 microg kg(-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.

The determination of biurea: a novel method to discriminate between nitrofurazone and azodicarbonamide use in food products.

Recently doubts have arisen on the usefulness of semicarbazide as marker residue for the illegal use of the antibiotic nitrofurazone (NFZ) in aquaculture and poultry production. Most notably azodicarbonamide (ADC) has been implicated as an alternative source of semicarbazide. ADC is used in some countries as a dough conditioner at concentrations up to 45 mg kg(-1). The use of ADC-treated flour or dough in coated or breaded food products may generate false non-compliant results in the analytical method for nitrofurazone metabolites, which is currently in use. During the dough preparation process ADC is largely reduced to biurea, which can be considered as an appropriate marker residue of ADC. Thus far no methods have been published for the determination of biurea in food commodities. Due to its polar nature it is very difficult to generate sufficient retention on conventional C18 HPLC columns. With a TSK amide HILIC type column good retention was obtained. A straightforward extraction-dilution protocol was developed. Using a mixture of dimethyl formamide and water biurea was nearly quantitatively extracted from a variety of fresh, coated and processed products. Mass spectrometric detection was performed with positive electrospray ionisation. The sensitivity and selectivity of the mass spectrometer for biurea was very good, allowing detection at concentrations as low as 10 microg kg(-1). However, in some extracts severe ion suppression effects was observed. To overcome the implications of ion suppression on the quantitative performance of the method an isotopically-labelled biurea internal standard was synthesized and incorporated in the method. The method developed can be used effectively in nitrofurazone analysis to eliminate the risk of false non-compliant results due to the presence of azodicarbonamide-treated components in the food product.