Identification and quantification of nitrofurazone metabolites by ultraperformance liquid chromatography–quadrupole time-of-flight high-resolution mass spectrometry with precolumn derivatization

Residue Depletion of Nitrofurazone Metabolites, Semicarbazide and 5-Nitro-2-Furaldehyde, in Broiler Chickens After Oral Administration

Nitrofurazone (NFZ) antibiotic is banned in food-producing animals, and its metabolite, semicarbazide (SEM), is used as a marker residue for nitrofurazone abuse. However, SEM can also be generated during food processing without veterinary treatment. Therefore, SEM cannot be considered an unequivocal marker of NFZ. This study investigates the use of 5-nitro-2-furaldehyde (5-NF) as an additional marker for nitrofurazone in broiler chickens. After oral administration of NFZ and 5-NF at 25 mg·kg-1 BW for 10 days, tissues (muscle and liver) and plasma samples were analyzed by liquid chromatography-tandem mass spectrometry. In NFZ-treated chickens, 5-NF was detected within 1 h in plasma at a peak concentration of 1.4 ± 0.25 μg·kg-1, while in 5-NF-treated ones, the maximum concentration was 0.85 ± 0.06 μg·kg-1 after 2 h. 5-NF was not detected in muscle and liver for both treated groups from 0 to 21 days. However, SEM persisted for up to 3 weeks in muscle (0.3 ± 0.018 μg·kg-1), 2 weeks in liver (0.16 ± 0.008 μg·kg-1), and 1 week in plasma (0.4 ± 0.05 μg·kg-1) with a faster elimination rate in liver tissues (half-life of 4.6 days) compared to muscle tissues (half-life of 6.5 days). These findings suggest that SEM remains a better marker for detecting nitrofurazone abuse in chickens compared to 5-NF.

Research progress on metabolites of nitrofurazone in aquatic products

The carcinogenic and teratogenic risks of nitrofurazone (NFZ) led to its restriction in aquatic products. Semicarbazide (SEM), one of its metabolites, is a primary focus of modern monitoring techniques. However, the SEM residue in aquatic products is believed to be formed through endogenous mechanisms, especially for aquatic crustaceans. In this article, we will discuss the source of SEM, including its usage as an antibiotic in aquatic products (nitrofurazone), its production during food processing (azodicarbonamide and hypochlorite treatment), its occurrence naturally in the body, and its intake from the environment. SEM detection techniques were divided into three groups: derivatization, extraction/purification, and analytical methods. Applications based on liquid chromatography and its tandem mass spectrometry, immunoassay, and electrochemical methods were outlined, as were the use of various derivatives and their assisted derivatization, as well as extraction and purification techniques based on liquid-liquid extraction and solid-phase extraction. The difficulties of implementing SEM for nitrofurazone monitoring in aquatic products from crustaceans are also discussed. Possible new markers and methods for detecting them are discussed. Finally, the present research on monitoring illicit nitrofurazone usage through its metabolites is summarised, and potential problems that need to be overcome by continuing research are proposed with an eye toward giving references for future studies.

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).

Determination of Antibiotic Residues in Aquaculture Products by Liquid Chromatography Tandem Mass Spectrometry: Recent Trends and Developments from 2010 to 2020

The issue of antibiotic residues in aquaculture products has aroused much concern over the last decade. The residues can remain in food and enter the human body through the food chain, posing great risks to public health. For the safety of foods and products, many countries have issued maximum residue limits and banned lists for antibiotics in aquaculture products. Liquid chromatography tandem mass spectrometry (LC/MS/MS) has been widely used for the determination of trace antibiotic residues due to its high sensitivity, selectivity and throughput. However, considering its matrix effects during quantitative measurements, it has high requirements for sample pre-treatment, instrument parameters and quantitative method. This review summarized the application of LC/MS/MS in the detection of antibiotic residues in aquaculture products in the past decade (from 2010 to 2020), including sample pre-treatment techniques such as hydrolysis, derivatization, extraction and purification, mass spectrometry techniques such as triple quadrupole mass spectrometry and high-resolution mass spectrometry as well as status of matrix certified reference materials (CRMs) and matrix effect.

Presence of nitrofurans and their metabolites in gelatine

Following the detection of semicarbazide (SEM) in gelatine by Italian Authorities, at levels exceeding by three times the reference point for action (RPA) of 1 μg/kg, set out by Commission Regulation (EU) 2019/1871 for nitrofurans and their metabolites, the European Commission mandated EFSA to investigate the available sources of nitrofurans and their metabolites in gelatine. European Commission also asked EFSA to provide approaches that would distinguish SEM occurring due to illegal treatment with nitrofurazone from SEM produced during food processing. The literature indicates that SEM, both free and bound to macromolecules, could occur also in food products such as gelatine, during food processing, arising from the use of disinfecting agents and/or from reactions of various food components and, therefore, SEM cannot be considered as an unequivocal marker of the abuse of nitrofurazone in animal production. It is recommended to investigate in more detail which processing conditions lead to the formation of SEM in gelatine during its production and what levels can be found. One potential approach to distinguishing between SEM from nitrofurazone and SEM from other sources in food products, such as gelatine, might be based on determining the ratio of bound:free SEM in a sample of gelatine. However, whether the ratio of bound:free SEM would unequivocally distinguish between SEM arising from nitrofurazone abuse or from other sources still needs to be demonstrated.

Determination of nitrofuran metabolites in honey using a new derivatization reagent, magnetic solid-phase extraction and LC-MS/MS

In this study, 5-nitro-2-furaldehyde (5-NFA) was proposed as a new derivatizing agent for nitrofuran metabolites. It reacts with nitrofuran metabolites producing the parent nitrofurans (furazolidone, furaltadone, nitrofurantoin, and nitrofurazone). Magnetic hypercrosslinked polystyrene (HCP/Fe₃O₄) was first used for magnetic solid phase extraction (MSPE) clean-up before the determination of nitrofuran metabolite derivatives in honey via LC-MS/MS. Main parameters affecting the derivatization and MSPE efficiency were investigated in detail and the optimal conditions were found. The method was validated using honey spiked with the four metabolites at 1, 2 and 200 μg kg^-1. Recoveries of >85% were achieved for the all analytes. The matrix calibration curve was fitted with the correlation coefficient (R²) > 0.99 in the range of 1-200 μg kg^-1. Precision values expressed as relative standard deviation (RSD) were <12% and <15% for intra-day and inter-day precision, respectively. The limits of detection (LODs) for the nitrofuran metabolites were of 0.1-0.3 μg kg^-1 and the limits of quantitation (LOQs) were of 0.3-1.0 μg kg^-1. The proposed LC-MS/MS method was applied to the analysis of real honey samples.

Tunable plasmonics of hollow raspberry-like nanogold for the robust Raman scattering detection of antibiotics on a portable Raman spectrometer

It is important to develop novel sensors for the simple, rapid, and quantitative detection of residual antibiotics in food, considering their potential threats to human health. Herein, we report the successful fabrication of raspberry-like nanogold (R-like Au) structures with rough surfaces and partially hollow structures for the rapid and sensitive detection of antibiotics in duck meats on a portable Raman spectrometer. The R-like Au with tunable plasmonic wavelengths was fabricated by a two-step method. Ag particles as seeds were substituted by Au particles through a replacement reaction; moreover, the surface plasmon resonances (SPRs) of R-like Au red-shifted with the increase in the Au ion concentration. The R-like Au with a diameter of about 120 nm that matched well with the 785 nm laser on the portable Raman spectrometer was used as an excellent surface-enhanced Raman spectroscopy (SERS) active platform for detecting two kinds of antibiotics, namely, nitrofurantoin (NFT) and nitrofurazone (NFZ), in spiked duck meats. Both of them have sufficient sensitivity (0.05-10 mg L-1), good linear relationship (R2 > 0.99) and high recovery in quantitative SERS analysis. The platform is simple without the need for complex pretreatment of the food samples or use of large scale Raman spectrometers, promising easy implementation for the on-site analysis of residuals of antibiotics in food.

Determination of 5-nitro-2-furaldehyde as marker residue for nitrofurazone treatment in farmed shrimps and with addressing the use of a novel internal standard

We developed a significantly improved ultra-high performance liquid chromatography-tandem mass spectrometry method for determination of 5-nitro-2-furaldehyde (NF) as a surrogate using a novel internal standard for the detection of nitrofurazone. We used 2,4-dinitrophenylhydrazine derivatization and furfural as the internal standard. Derivatization was easily performed in HCl using ultrasonic manipulation for 5 min followed by liquid extraction using ethyl acetate. The samples were concentrated and purified using reverse phase and alumina cartridges in tandem. The derivatives were separated using a linear gradient elution on a C₁₈ column with methanol and water as the mobile phase in negative ionization mode and multiple reaction monitoring. Under the optimized conditions, the calibration curves were linear from 0.2 to 20 μg/L with correlation coefficients >0.999. Mean recoveries were 80.8 to 104.4% with the intra- and inter-day relative standard deviations <15% at spiking levels of 0.1 to 10 μg/kg. The limits of detection and quantification were 0.05 and 0.1 μg/kg, respectively. This method is a robust tool for the identification and quantitative determination of NF in shrimp samples.