Fluorescent probe of quantum dots and zinc oxide in a highly selective polymer simultaneously determined florfenicol and sparfloxacin

A nanocomposite fluorescent probe was fabricated for the simultaneous determination of florfenicol and sparfloxacin based on fluorescence quenching. The probe was synthesized by integrating nitrogen-doped graphene quantum dots (N-GQDs), cadmium telluride quantum dots (CdTe QDs) and zinc oxide nanoparticles (ZnO) into a molecularly imprinted polymer (MIP). The determination was based on the quenching of fluorescence emissions from N-GQDs by florfenicol, detected at 410 nm, and the quenching of fluorescence emissions from CdTe QDs by sparfloxacin, detected at 550 nm. The fluorescent probe was highly sensitive and specific with good linear relationships for florfenicol and sparfloxacin in the range  0.10 to 100.0 μg L-1. The limits of detection for florfenicol and sparfloxacin were 0.06 and 0.10 μg L-1, respectively. The fluorescent probe was used to determine florfenicol and sparfloxacin in food samples and the results agreed well with the results of chromatographic determination. Recoveries of spiked milk, egg and chicken samples reached 93.3-103.4% with good precision (RSD < 6%). The advantages of the nano-optosensor include high sensitivity and selectivity, simplicity, rapidity, convenience, good accuracy and precision.

The bacterial microbiota in florfenicol contaminated soils: The antibiotic resistome and the nitrogen cycle

Soil antibiotic resistome and the nitrogen cycle are affected by florfenicol addition to manured soils but their interactions have not been fully described. In the present study, antibiotic resistance genes (ARGs) and nitrogen cycle genes possessed by soil bacteria were characterized using real-time fluorescence quantification PCR (qPCR) and metagenomic sequencing in a short-term (30 d) soil model experiment. Florfenicol significantly changed in the abundance of genes conferring resistance to aminoglycosides, β-lactams, tetracyclines and macrolides. And the abundance of Sphingomonadaceae, the protein metabolic and nitrogen metabolic functions, as well as NO reductase, nitrate reductase, nitrite reductase and N₂O reductase can also be affected by florfenicol. In this way, ARG types of genes conferring resistance to aminoglycosides, β-lactamases, tetracyclines, colistin, fosfomycin, phenicols and trimethoprim were closely associated with multiple nitrogen cycle genes. Actinobacteria, Chlorobi, Firmicutes, Gemmatimonadetes, Nitrospirae, Proteobacteria and Verrucomicrobia played an important role in spreading of ARGs. Moreover, soil physicochemical properties were important factors affecting the distribution of soil flora. This study provides a theoretical basis for further exploration of the transmission regularity and interference mechanism of ARGs in soil bacteria responsible for nitrogen cycle.

Capped cadmium sulfide quantum dots with a new ionic liquid as a fluorescent probe for sensitive detection of florfenicol in meat samples

The new ionic liquid capped CdS quantum dots (IL-CdS QDs) as a fluorescent probe was successfully synthesized by a hydrothermal method in a one step process and used for the facile and sensitive determination of florfenicol (FLF) in aqueous media. The new ionic liquid 3-(2-[(5-amino-1,3,4-thiadiazol-2-yl)thio]ethyl)-1-methyl-1H-imidazol-3-ium chloride (IL) was synthesized by introducing 5-amino-1,3,4-thiadiazole-2-thiol as a ligand onto the alkyl chain of the 1-chloroethyl-3-methylimidazolium chloride ILs. This task specific ionic liquid reagent was used for the capping of CdS QDs which played the role of recognition element of FLF. The IL-CdS QDs were characterized by Ultra Violet-Visible absorption -spectroscopy (UV-Vis absorption spectroscopy), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Quenching of fluorescence intensity of the IL-CdS QDs was in proportion to the addition of FLF concentration. Under the optimum conditions, the fluorescence intensity ratio of IL-CdS QDs in the presence and absence of FLF versus FLF concentrations gave a linear response according to the Stern-Volmer equation from 0.1 to 20 μg mL^-1 (0.3 to 56 μmol L^-1) with a limit of detection 0.035 μg mL^-1 (0.098 μmol L^-1). The developed method was applied to the determination of FLF in fish and chicken meats with satisfactory results. This method revealed some advantages such as high sensitivity, precision and wide linear range to FLF. The proposed method can be utilized for rapid screening the quality of meat products.

Multimedia fate modeling of antibiotic sulfamethoxazole, lincomycin, and florfenicol in a seasonally ice-covered river receiving WWTP effluents

As a result of the widespread use of antibiotics, a large amount of excretions from human and animals, containing antibiotic residues, is discharged into aquatic environments, leading to potential adverse effects on the ecosystems' health. These residues' impact on seasonally ice-covered rivers remains under investigated. To understand the environmental fate of antibiotics with high-detection frequencies and concentration levels, sulfamethoxazole, lincomycin, and florfenicol were used as models in the present study. A Level IV fugacity model was established and applied to a seasonally ice-covered river receiving municipal wastewater treatment plant (WWTP) effluents, the Songhua River in Northeast China. Model validation and sensitivity analysis suggested that the fugacity model could successfully simulate the monitoring concentration within an average difference of one logarithmic unit. The advection process played a major role in the transport and attenuation of the antibiotics in the ice-covered river receiving WWTP effluents. The scenario simulation indicated that increasing the targeted antibiotic concentrations in WWTP effluents to μg L^-1 could keep the targeted antibiotic concentrations higher than 10 ng L^-1 in the receiving river from the WWTP discharge source to 25 km downstream. This finding also demonstrates that the depth of water and ice, as well as flow velocity, play key roles in the fate of antibiotics in the ice-covered river receiving WWTP effluents. To our best knowledge, this is the first major study to combine experimental investigation with modeling to explore the environmental behaviors and fate of antibiotics in such a river.

Development and comparison of liquid-liquid extraction and accelerated solvent extraction methods for quantitative analysis of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in poultry eggs

Accelerated solvent extraction was investigated as a novel alternative technology for the separation and quantitative analysis of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine from poultry eggs, and the results were compared with the results of liquid-liquid extraction. Rapid quantification of the target compounds was carried out by ultra-performance liquid chromatography-electrospray ionization tandem triple quadrupole mass spectrometry. This optimized method was validated according to the requirements defined by the European Union and the United States Food and Drug Administration. Finally, the new approach was successfully applied to the quantitative determination of these analytes in 90 commercial poultry eggs from local supermarkets.

Evaluation of the leaching of florfenicol from coated medicated fish feed into water

Florfenicol is one of the most-used antimicrobial agents in global fish farming. Nevertheless, in most countries, its use is not conducted in accordance with good practices. The aim of this work was to evaluate the leaching of florfenicol from coated fish feed into the water. Analytical methods were developed and validated for the quantitation of florfenicol in medicated feed and water by UHPLC-MS/MS. Florfenicol residues in the water were quantified after 5- and 15-min exposures of the medicated feed in the water at 22 and 28 °C and at pH 4.5 and 8.0. The influence of pellet size and three coating agents (vegetable oil, carboxymethylcellulose, and low-methoxylated pectin) on the leaching of the drug was also assessed. Pellet size, coating agent, water temperature, and time of exposure significantly (p < 0.05) affected florfenicol leaching, while water pH did not interfere with the leaching. Coating with vegetable oil was the most efficient method to reduce florfenicol leaching, while coating with carboxymethylcellulose presented the highest leaching (approximately 60% after 15 min at 28 °C). Thus, the coating agent has a significant effect on the florfenicol leaching rate and, consequently, on the necessary dose of the drug to be administered. Moreover, it is worth mentioning that higher florfenicol leaching will pose a greater risk to environmental health, specifically in terms of the development of bacteria resistant to florfenicol. Additional studies are needed with other polymers and veterinary drugs used in medicated feed for fish farming.

Residue Depletion of Florfenicol and Florfenicol Amine in Broiler Chicken Claws and a Comparison of Their Concentrations in Edible Tissues Using LC⁻MS/MS

Antimicrobial residues might persist in products and by-products destined for human or animal consumption. Studies exploring the depletion behavior of florfenicol residues in broiler chicken claws are scarce, even though claws can enter the food chain directly or indirectly. Hence, this study intended to assess the concentrations of florfenicol (FF) and florfenicol amine (FFA)—its active metabolite—in chicken claws from birds that were treated with a therapeutic dose of florfenicol. Furthermore, concentrations of these analytes in this matrix were compared with their concentrations in edible tissues at each sampling point. A group of 70 broiler chickens were raised under controlled conditions and used to assess residue depletion. Sampling points were on days 5, 10, 20, 25, 30, 35, and 40 after ceasing treatment, thus extending beyond the withdrawal period established for muscle tissue (30 days). Analytes were extracted using HPLC-grade water and acetone, and dichloromethane was used for the clean-up stage. Liquid chromatography coupled to mass spectroscopy detection (LC–MS/MS) was used to detect and quantify the analytes. The analytical methodology developed in this study was validated in-house and based on the recommendations described in the Commission Decision 2002/657/EC from the European Union. Analyte concentrations were calculated by linear regression analysis of calibration curves that were fortified using an internal standard of chloramphenicol-d₅ (CAF-d₅). The depletion time of FF and FFA was set at 74 days in claws, based on a 95% confidence level and using the limit of detection (LOD) as the cut-off point. Our findings show that FF and FFA can be found in chicken claws at higher concentrations than in muscle and liver samples at each sampling point.

Accurate Quantitation and Analysis of Nitrofuran Metabolites, Chloramphenicol, and Florfenicol in Seafood by Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry: Method Validation and Regulatory Samples

We developed and validated a method for the extraction, identification, and quantitation of four nitrofuran metabolites, 3-amino-2-oxazolidinone (AOZ), 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ), semicarbazide (SC), and 1-aminohydantoin (AHD), as well as chloramphenicol and florfenicol in a variety of seafood commodities. Samples were extracted by liquid-liquid extraction techniques, analyzed by ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), and quantitated using commercially sourced, derivatized nitrofuran metabolites, with their isotopically labeled internal standards in-solvent. We obtained recoveries of 90-100% at various fortification levels. The limit of detection (LOD) was set at 0.25 ng/g for AMOZ and AOZ, 1 ng/g for AHD and SC, and 0.1 ng/g for the phenicols. Various extraction methods, standard stability, derivatization efficiency, and improvements to conventional quantitation techniques were also investigated. We successfully applied this method to the identification and quantitation of nitrofuran metabolites and phenicols in 102 imported seafood products. Our results revealed that four of the samples contained residues from banned veterinary drugs.

Antibiotics in Crab Ponds of Lake Guchenghu Basin, China: Occurrence, Temporal Variations, and Ecological Risks

Antibiotics are widely used in aquaculture, however, this often results in undesirable ecological effects. To evaluate the occurrence, temporal variations, and ecological risk of antibiotics in five crab ponds of Lake Guchenghu Basin, China, 44 antibiotics from nine classes were analyzed by rapid resolution liquid chromatography-tandem mass spectrometry (RRLC-MS/MS). Twelve antibiotics belonging to six classes were detected in the aqueous phase of five crab ponds, among which sulfonamides and macrolides were the predominant classes, and six compounds (sulfamonomethoxine, sulfadiazine, trimethoprim, erythromycin-H₂O, monensin, and florfenicol) were frequently detected at high concentrations. In general, the antibiotic levels varied between different crab ponds, with the average concentrations ranging from 122 to 1440 ng/L. The antibiotic concentrations in crab ponds exhibited obvious seasonal variations, with the highest concentration and detection frequency detected in summer. Multivariate analysis showed that antibiotic concentrations were significantly correlated with environmental variables, such as total organic carbon, phosphate, ammonia nitrogen, and pH. Sulfadiazine, clarithromycin, erythromycin-H₂O, and ciprofloxacin posed a high risk to algae, while the mixture of antibiotics could pose a high risk to aquatic organisms in the crab ponds. Overall, the usage of antibiotics in farming ponds should be comprehensively investigated and controlled to preserve a healthy aquaculture ecosystem.

Effect of florfenicol on performance and microbial community of a sequencing batch biofilm reactor treating mariculture wastewater

The effects of florfenicol (FF) on the performance, microbial activity and microbial community of a sequencing batch biofilm reactor (SBBR) were evaluated in treating mariculture wastewater. The chemical oxygen demand (COD) and nitrogen removal were inhibited at high FF concentrations. The specific oxygen utilization rate (SOUR), specific ammonium oxidation rate (SAOR), specific nitrite oxidation rate (SNOR) and specific nitrate reduction rate (SNRR) were decreased with an increase in the FF concentration from 0 to 35 mg/L. The chemical compositions of loosely bound extracellular polymeric substances (LB-EPS) and tightly bound EPS (TB-EPS) could be affected with an increase in the FF concentration. The high-throughput sequencing indicated some obvious variations in the microbial community at different FF concentrations. The relative abundance of Nitrosomonas and Nitrospira showed a decreasing tendency with an increase in the FF concentration, suggesting that FF could affect the nitrification process of SBBR. Some genera capable of reducing nitrate to nitrogen gas could be inhibited by the addition of FF in the influent, such as Azospirillum and Hyphomicrobium.

Effect of forestry-waste biochars on adsorption of Pb(II) and antibiotic florfenicol in red soil

Biochars derived from Pinus massoniana and Cunninghamia lanceolata trunks (abbreviated as PB and CB, respectively) were used to investigate their potential capabilities to improve lead (Pb(II)) and antibiotic florfenicol (FLO) immobilization in soil. Results shows that, after incubation for 60 days, the maximum adsorption capacities (Q _m ) of biochar-treated soils (soil-PB and soil-CB) for Pb(II) was increased by 27 and 14 %, respectively, compared with pristine soil sample. In the case of FLO, however, the Q _m of biochar-treated soils were enhanced by 266 and 206 % for soil-PB and soil-CB, respectively. The increased Pb(II) adsorption was mainly due to the enhanced interactions between Pb(II) and oxygen-containing functional groups and aromatic structures in biochars. Whereas, the improvement of FLO adsorption was achieved through electrostatic interaction, hydrogen bonding, and van der Waals forces interactions between FLO molecule and biochars. Regardless of the similarities in chemical compositions between two biochars, significantly higher surface area and total pore volume of PB than CB biochar may be the key factors accounting for the differences in adsorption efficiencies for Pb(II) and FLO between Soil-PB and Soil-CB.

The development of a new optical sensor based on the Mn doped ZnS quantum dots modified with the molecularly imprinted polymers for sensitive recognition of florfenicol

The Mn doped ZnS quantum dots (Mn:ZnS QDs) capped with the florfenicol molecularly imprinted polymer (Mn:ZnS QDs@MIP) were prepared via the sol-gel surface imprinting approach using 3-aminopropyltriethoxysilane (APTES) as the functional monomer and tetraethoxysilane (TEOS) as the cross-linker for the optosensing of the florfenicol. Transmission electron microscopy (TEM), X-ray diffractometer, IR spectroscopy, UV-Vis absorption spectrophotometry, and spectrofluorometry were used to elucidate the formation, morphology, and identification of the products. To illustrate the usefulness of the new imprinted material, the non-imprinted coated Mn:ZnS QDs (Mn:ZnS QDs@NIP) were synthesized without the presence of the florfenicol. It was revealed that the fluorescence (FL) intensity of the Mn:ZnS QDs@MIP increased with increasing the FF concentration. Under the optimal conditions, changes in the FL intensity in the presence of the target molecule showed a linear response in the concentration range of 30-700 μmol L(-1) with a detection limit of 24 μmol L(-1). The developed method was finally applied successfully to the determination of FF in different meat samples with satisfactory recoveries.

Aqueous photodegradation of antibiotic florfenicol: kinetics and degradation pathway studies

The occurrence of antibacterial agents in natural environment was of scientific concern in recent years. As endocrine disrupting chemicals, they had potential risk on ecology system and human beings. In the present study, the photodegradation kinetics and pathways of florfenicol were investigated under solar and xenon lamp irradiation in aquatic systems. Direct photolysis half-lives of florfenicol were determined as 187.29 h under solar irradiation and 22.43 h under xenon lamp irradiation, respectively. Reactive oxygen species (ROS), such as hydroxyl radical (·OH) and singlet oxygen ((1)O2) were found to play an important role in indirect photolysis process. The presence of nitrate and dissolved organic matters (DOMs) could affect photolysis of florfenicol in solutions through light screening effect, quenching effect, and photoinduced oxidization process. Photoproducts of florfenicol in DOMs solutions were identified by solid phase extraction-liquid chromatography-mass spectrometry (SPE-LC-MS) analysis techniques, and degradation pathways were proposed, including photoinduced hydrolysis, oxidation by (1)O2 and ·OH, dechlorination, and cleavage of the side chain.

Determination of florfenicol residues in broiler meat and liver samples using RP-HPLC with UV-visible detection

BACKGROUND

Broilers are vulnerable to various types of microorganisms, including Salmonella, Escherichia coli and Staphylococcus aureus, resulting in multiple infections. Broad-spectrum antibacterial drugs such as florfenicol (FF) are widely used in the treatment of such infections. Suspected residues of these drugs in body tissues of treated birds can be passed to humans through meat consumption and thus lead to serious ill effects on human health. The present study was designed to estimate the presence of FF residues in broiler meat and liver samples.

RESULTS

The mean residual concentrations of FF in broiler meat and liver samples were 311.42 ± 186.56 and 2585.44 ± 1759.71 µg kg(-1) respectively, which are higher than their respective maximum residual limits (MRLs). The results showed that 126 and 24 samples were FF-positive and FF-negative respectively. Of the positive samples, 84 and 42 samples were above and below the MRL respectively.

CONCLUSION

The results indicate the presence of FF residues in broiler meat and liver samples. Usage of this contaminated meat causes resistance in consumers and poses a public health threat. Thus there is a need to educate farmers about the ill effects of residual drugs on human health and their withdrawal times in poultry. © 2015 Society of Chemical Industry.

Antibiotics in Drinking Water in Shanghai and Their Contribution to Antibiotic Exposure of School Children

A variety of antibiotics have been found in aquatic environments, but antibiotics in drinking water and their contribution to antibiotic exposure in human are not well-explored. For this, representative drinking water samples and 530 urine samples from schoolchildren were selected in Shanghai, and 21 common antibiotics (five macrolides, two β-lactams, three tetracyclines, four fluoquinolones, four sulfonamides, and three phenicols) were measured in water samples and urines by isotope dilution two-dimensional ultraperformance liquid chromatography coupled with high-resolution quadrupole time-of-flight mass spectrometry. Drinking water included 46 terminal tap water samples from different spots in the distribution system of the city, 45 bottled water samples from 14 common brands, and eight barreled water samples of different brands. Of 21 antibiotics, only florfenicol and thiamphenicol were found in tap water, with the median concentrations of 0.0089 ng/mL and 0.0064 ng/mL, respectively; only florfenicol was found in three bottled water samples from a same brand, with the concentrations ranging from 0.00060 to 0.0010 ng/mL; no antibiotics were found in barreled water. In contrast, besides florfenicol and thiamphenicol, an additional 17 antibiotics were detected in urine samples, and the total daily exposure doses and detection frequencies of florfenicol and thiamphenicol based on urine samples were significantly and substantially higher than their predicted daily exposure doses and detection frequencies from drinking water by Monte Carlo Simulation. These data indicated that drinking water was contaminated by some antibiotics in Shanghai, but played a limited role in antibiotic exposure of children.

Occurrence of 13 veterinary drugs in animal manure-amended soils in Eastern China

The occurrence of 13 veterinary drugs were studied in soil fertilized with animal manures in Eastern China. The 69 soil samples were obtained from twenty-three vegetable fields in 2009 and analysed for selected veterinary drugs by HPLC-MS/MS at soil depths of 0-20, 20-40 and 40-60 cm, and two additional samples were re-analysed from an earlier study from November 2011. Results showed that animal wastes, especially those from poultry farms, were one of pollution sources of veterinary drugs in soil. The detection frequency of veterinary drugs in soil was 83%, 91% and 87% in the three soil depths, respectively. The detection rates for the five classes of drugs in soils followed the rank order cyromazine > tetracyclines > sulfonamides > fluoroquinolones > florfenicol. Veterinary drugs were detected in soil layers at 20-40 and 40-60 cm depth to a greater extent than at 0-20 cm depth. The results of the same point in years 2009 and 2011 indicated that veterinary drugs accumulate easily and persist in the deeper soil. In addition, residue levels of veterinary drugs in soil were related to the animal species the manure was derived from. Overall, the predominance of tetracyclines in sampled soils underscored the need to regulate their veterinary use in order to improve the management and treatment of associated releases.

Hydrolysis of amphenicol and macrolide antibiotics: Chloramphenicol, florfenicol, spiramycin, and tylosin

Antibiotics that enter the environment can present human and ecological health risks. An understanding of antibiotic hydrolysis rates is important for predicting their environmental persistence as biologically active contaminants. In this study, hydrolysis rates and Arrhenius constants were determined as a function of pH and temperature for two amphenicol (chloramphenicol and florfenicol) and two macrolide (spiramycin and tylosin) antibiotics. Antibiotic hydrolysis rates in pH 4-9 buffer solutions at 25°C, 50°C, and 60°C were quantified, and degradation products were characterized. All of the antibiotics tested remained stable and exhibited no observable hydrolysis under ambient conditions typical of aquatic ecosystems. Acid- and base-catalyzed hydrolysis occurred at elevated temperatures (50-60°C), and hydrolysis rates increased considerably below pH 5 and above pH 8. Hydrolysis rates also increased approximately 1.5- to 2.9-fold for each 10°C increase in temperature. Based on the degradation product masses found, the functional groups that underwent hydrolysis were alkyl fluoride, amide, and cyclic ester (lactone) moieties; some of the resultant degradation products may remain bioactive, but to a lesser extent than the parent compounds. The results of this research demonstrate that amphenicol and macrolide antibiotics persist in aquatic systems under ambient temperature and pH conditions typical of natural waters. Thus, these antibiotics may present a risk in aquatic ecosystems depending on the concentration present.

Dispersive liquid-liquid microextraction method based on solidification of floating organic droplet for the determination of thiamphenicol and florfenicol in environmental water samples

Dispersive liquid-liquid microextraction with solidification of a floating organic droplet (DLLME-SFO) followed by high performance liquid chromatography-ultraviolet (HPLC-UV) detection was applied for the determination of thiamphenicol (TAP), florfenicol (FF) in water samples. 1-Undecanol was used as the extraction solvent which has lower density than water, low toxicity, and low melting point (19°C). A mixture of 800mL acetone (disperser solvent) and 80µL of 1-undecanol (extraction solvent) was injected into 20mL of aqueous solution. After 5min, 0.6g of NaCl was added and the sample vial was shaken. After 5min, the sample was centrifuged at 3500rpm for 3min, and then placed in an ice bath. When the extraction solvent floating on the aqueous solution had solidified, it was transferred into another conical vial where it was melted quickly at room temperature, and was diluted with methanol to 1mL, and analyzed by HPLC-UV detection. Parameters influencing the extraction efficiency were thoroughly examined and optimized. The extraction recoveries (ER) and the enrichment factors (EF) ranged from 67% to 72% and 223 to 241, respectively. The limits of detection (LODs) (S/N=3) were 0.33 and 0.56µgL(-1) for TAP and FF, respectively. Linear dynamic range (LDR) was in the range of 1.0-550µgL(-1) for TAP and 1.5-700µgL(-1) for FF, the relative standard deviations (RSDs) were in the range of 2.6-3.5% and the recoveries of spiked samples ranged from 94% to 106%.

Quality of Antimicrobial Products Used in Striped Catfish (Pangasianodon hypophthalmus) Aquaculture in Vietnam

Antimicrobial usage is common in Asian aquaculture. This study aimed to determine the quality of antimicrobial products used by Vietnamese striped catfish (Pangasianodon hypophthalmus) farmers. Twenty one antimicrobial products (11 products contained a single antimicrobial and 10 products contained a mixture of two different antimicrobials) commonly used by catfish farmers were obtained from so-called chemical shops located in the Mekong Delta, Vietnam. Ultra High Performance Liquid Chromatography Mass Spectrometry was used to analyze concentration of sulfonamides, trimethoprim, amoxicillin, cefalexin and ciprofloxacin whereas concentrations of florfenicol and doxycycline were analyzed by High Performance Liquid Chromatography with UV detection. Results revealed that only 4/11 products with a single antimicrobial and 2/10 products with a mixture of antimicrobials contained active substances within ±10% of the concentration declared on the product label. Two products with antimicrobial mixtures did not contain any of the declared antimicrobials. Comparing two batches, analysis of 11 products revealed that only one product contained a concentration of active compound that varied with less than 10% in both batches. Several product labels provided inadequate information on how to calculate therapeutic dosage and further stated withdrawal time despite lack of pharmacokinetic data on the antimicrobials in catfish. There is an urgent need to strengthen approval procedures and in particular regularly to monitor the quality of antimicrobials used in Vietnamese aquaculture.

Concentration-dependent photodegradation kinetics and hydroxyl-radical oxidation of phenicol antibiotics

Thiamphenicol and florfenicol are two phenicol antibiotics widely used in aquaculture and are ubiquitous as micropollutants in surface waters. The present study investigated their photodegradation kinetics, hydroxyl-radical (OH) oxidation reactivities and products. Firstly, the photolytic kinetics of the phenicols in pure water was studied as a function of initial concentrations (C0) under UV-vis irradiation (λ>200nm). It was found that the kinetics was influenced by C0. A linear plot of the pseudo-first-order rate constant vs C0 was observed with a negative slope. Secondly, the reaction between the phenicol antibiotics and OH was examined with a competition kinetic method under simulated solar irradiation (λ>290nm), which quantified their bimolecular reaction rate constants of (2.13±0.02)×10(9)M(-1)s(-1) and (1.82±0.10)×10(9)M(-1)s(-1) for thiamphenicol and florfenicol, respectively. Then the corresponding OH oxidated half-lives in sunlit surface waters were calculated to be 90.5-106.1h. Some main intermediates were formed from the reaction, which suggested that the two phenicols underwent hydroxylation, oxygenation and dehydrogenation when OH existed. These results are of importance to assess the phenicol persistence in wastewater treatment and sunlit surface waters.

Development of a rapid chemiluminescent ciELISA for simultaneous determination of florfenicol and its metabolite florfenicol amine in animal meat products

BACKGROUND

A rapid one-step chemiluminescent competitive indirect enzyme-linked immunosorbent assay (CL-ciELISA) for florfenicol (FF) and its major metabolite florfenicol amine (FFA) residues in animal meat products has been developed.

RESULTS

The 50% binding inhibition (IC₅₀) values of the method were 0.195 µg kg⁻¹ for FFA and 0.24 µg kg⁻¹ for FF under optimum conditions. The cross-reactive rates for FF and FFA were 100.0% and 81.2%, respectively. FF and FFA were easily extracted from animal meat product with an FF/FFA extraction buffer, obtaining recoveries of 81.8-92.0% (FF) and 77.2-100% (FFA). The whole one-step CL-ciELISA test can be accomplished within 40 min in theory. The detection limits (LODs) of the assay were 0.98 µg kg⁻¹ for FF and 0.80 µg kg⁻¹ for FFA in animal meat samples. Finally, field animal meat samples were analyzed with the CL-ciELISA method, and the results correlated well with those obtained using traditional ELISA and a previously reported liquid chromatographic-tandem mass spectrometric method.

CONCLUSION

The combined results confirmed the utility of this faster one-step CL-ciELISA for simultaneous trace analysis of FF and FFA. To date, this is the most rapid developed ELISA and CL-ELISA method for detection of FF and FFA.

Preparation of artificial antigen and egg yolk-derived immunoglobulin (IgY) of florfenicol amine for ELISA assay

To investigate the feasibility of IgY technology for the immune detection of haptens, a specific egg yolk antibody (IgY) has been developed in order to detect the florfenicol amine (FFA) residues. FFA was conjugated to bovine serum albumin (BSA) by glutaraldehyde (GA) and the conjugate was used to immunize laying chickens. Anti-FFA IgY antibody was purified by PEG-6000 precipitation and identified by SDS-PAGE. The titer of anti-FFA IgY antibody reached a peak of 1:128,000 after three booster injections. Checkerboard titration showed that a 1:800 dilution of anti-FFA IgY could give an optical density (OD) at around 1.0 at 10 μg/mL FFA-OVA coating concentration. An indirect competitive enzyme-linked immunosorbent assay (icELISA) using specific anti-FFA IgY showed that the IC50 value of anti-FFA IgY was 12.30 ng/mL and the regression curve equation was y = -13.71x + 64.95 (R (2) = 0.945). The strategy of developing anti-hapten IgY antibody is that it may be further used as a new reagent for an immunoassay of hapten residues.

Atmospheric pressure ionization-tandem mass spectrometry of the phenicol drug family

In this work, the mass spectrometry behaviour of the veterinary drug family of phenicols, including chloramphenicol (CAP) and its related compounds thiamphenicol (TAP), florfenicol (FF) and FF amine (FFA), was studied. Several atmospheric pressure ionization sources, electrospray (ESI), atmospheric pressure chemical ionization and atmospheric pressure photoionization were compared. In all atmospheric pressure ionization sources, CAP, TAP and FF were ionized in both positive and negative modes; while for the metabolite FFA, only positive ionization was possible. In general, in positive mode, [M + H](+) dominated the mass spectrum for FFA, while the other compounds, CAP, TAP and FF, with lower proton affinity showed intense adducts with species present in the mobile phase. In negative mode, ESI and atmospheric pressure photoionization showed the deprotonated molecule [M-H](-), while atmospheric pressure chemical ionization provided the radical molecular ion by electron capture. All these ions were characterized by tandem mass spectrometry using the combined information obtained by multistage mass spectrometry and high-resolution mass spectrometry in a quadrupole-Orbitrap instrument. In general, the fragmentation occurred via cyclization and losses or fragmentation of the N-(alkyl)acetamide group, and common fragmentation pathways were established for this family of compounds. A new chemical structure for the product ion at m/z 257 for CAP, on the basis of the MS(3) and MS(4) spectra is proposed. Thermally assisted ESI and selected reaction monitoring are proposed for the determination of these compounds by ultra high-performance liquid chromatography coupled to tandem mass spectrometry, achieving instrumental detection limits down to 0.1 pg.

Development and validation of a method for the simultaneous extraction and separate measurement of oxytetracycline, florfenicol, oxolinic acid and flumequine from marine sediments

A simple and rapid method for the detection and extraction of oxolinic acid, flumequine, florfenicol and oxytetracycline from marine sediments was developed and validated. The analytes were extracted from the marine sediment using a solution of oxalic acid diluted in methanol with sonication before detection by HPLC using a diode-array detector (florfenicol and oxytetracycline) and fluorescence (oxolinic acid and flumequine). The quantification limits (QL) were 100 ng/g for oxytetracycline and florfenicol and 5 ng/g for oxolinic acid and flumequine. The coefficients of variation of the repeatability and intermediate precision were less than 10% in all of the analytes. The calibration curves were linear between 50 and 500 ng/ml for oxytetracycline and florfenicol and 1 and 20 ng/ml for oxolinic acid and flumequine. The recuperation rate for the analytes was above 86%.

Florfenicol depletion in edible tissue of rainbow trout, Oncorhynchus mykiss (Walbaum), and sea bream, Sparus aurata L

An increase in fish production has consequently brought an increase in infectious diseases in fish farms. The use of chemotherapic drugs is the most effective instrument against common bacterial agents. The number of registered drugs for use in aquaculture is limited and often veterinary practitioners resort to the off-label use of chemotherapic agents authorized for different food-producing animal species. Florfenicol is well known for its outstanding effect against various pathogenic bacteria affecting fish, and therefore, it may be a useful drug for off-label use in aquaculture. The aim of this study was to evaluate the depletion of florfenicol and its major metabolite, florfenicol amine, from the edible tissue of two fish species, rainbow trout and sea bream, following treatment with medicated feed at a dosage of 10 mg kg(-1) of bw day(-1) , for 10 consecutive days. At prefixed time points after the end of administration (0.25, 1, 2, 3, 4, 6, 7, 10, 14 and 21 days after treatment), edible tissues (muscle plus adherent skin) from 15 individuals in each group were collected and analysed by HPLC, to determine concentration of the drug in the tissue. On the basis of the obtained concentrations, withdrawal times of florfenicol in the two species were calculated. The results indicate that a drug withdrawal time of 500 °C-day, as established by Directive 2004/28/EC, for off-label drug use is more than satisfactory to guarantee the healthiness of fish products against the risk of drug residues.

Fate of florfenicol in a simulated aquatic ecosystem and effects on sediment microflora

Four controlled microcosms were prepared, one of which served as control, whereas the other three received treatments of 10, 50, and 150 mg/L of florfenicol, an antibacterial drug developed initially for aquaculture applications. Water and sediment samples were collected according to a pre-set time schedule to determine its fate in the aquatic environment. The results demonstrated that florfenicol amine was not detectable in any treatment groups. The half-life of florfenicol in pond water was 30.76, 52.92, and 51.48 hours for the 10, 50, and 150 mg/L treatment groups, respectively; the corresponding half-lives in sediment were 25.42, 38.40, and 53.59 days. Further, the 50 and 150 mg/L florfenicol treatment groups inhibited alkaline protease activity; however, all treatment groups inhibited sediment microflora structural diversity.

Occurrence of ciprofloxacin, enrofloxacin, and florfenicol in animal wastewater and water resources

Antimicrobial agent residues are becoming an intractable environmental problem in soil, surface, and underground water. To obtain a broad profile of residues in animal wastewater and surface water, 24 animal wastewater, 8 animal farm effluent, 18 river water, and 8 pond water samples taken in Jiangsu in eastern China were monitored for enrofloxacin, ciprofloxacin, and florfenicol using solid phase extraction and high performance liquid chromatography/electrospray ionization-tandem mass spectrometry (HPLC/ESI-MS/MS) techniques. The results revealed that two antibacterials were detected simultaneously in 49.1% of samples, followed by three antibacterials (22.6%) and one antibacterial (22.6%). Up to 3.35, 5.93, and 2.10 μg L for ciprofloxacin, 1.09, 4.24, and 0.50 μg L for enrofloxacin, and 0.95, 2.40, and 2.84 μg L for florfenicol were detected in animal farm-effluent, river, and pond water, respectively. The maximum concentrations of ciprofloxacin and enrofloxacin in animal wastewaters were 7.49 and 8.77 μg L, respectively. Furthermore, residue levels of ciprofloxacin and florfenicol showed at least two statistical differences between any two sampling areas or two animal farms. Enrofloxacin showed no statistical difference among the sampling areas and the animal farms.

Salmon aquaculture and antimicrobial resistance in the marine environment

Antimicrobials used in salmon aquaculture pass into the marine environment. This could have negative impacts on marine environmental biodiversity, and on terrestrial animal and human health as a result of selection for bacteria containing antimicrobial resistance genes. We therefore measured the numbers of culturable bacteria and antimicrobial-resistant bacteria in marine sediments in the Calbuco Archipelago, Chile, over 12-month period at a salmon aquaculture site approximately 20 m from a salmon farm and at a control site 8 km distant without observable aquaculture activities. Three antimicrobials extensively used in Chilean salmon aquaculture (oxytetracycline, oxolinic acid, and florfenicol) were studied. Although none of these antimicrobials was detected in sediments from either site, traces of flumequine, a fluoroquinolone antimicrobial also widely used in Chile, were present in sediments from both sites during this period. There were significant increases in bacterial numbers and antimicrobial-resistant fractions to oxytetracycline, oxolinic acid, and florfenicol in sediments from the aquaculture site compared to those from the control site. Interestingly, there were similar numbers of presumably plasmid-mediated resistance genes for oxytetracycline, oxolinic acid and florfenicol in unselected marine bacteria isolated from both aquaculture and control sites. These preliminary findings in one location may suggest that the current use of large amounts of antimicrobials in Chilean aquaculture has the potential to select for antimicrobial-resistant bacteria in marine sediments.

The operation of two EGSB reactors under the application of different loads of oxytetracycline and florfenicol

This study evaluated the effect of the antibiotics oxytetracycline (OTC) and florfenicol (FLO) on the operation of two EGSB (expanded granular sludge bed) reactors. The experiment was conducted for 210 d in reactor R1 and 245 d in reactor R2. The reactors were inoculated with granular sludge from a upflow anaerobic sludge blanket (UASB) reactor on a local dairy farm. The sludge had an average pellet size of 2.35 mm, good sedimentability and a high percentage of organic material. The antibiotic tolerance and the inhibitory action on the bacterial population were different for each antibiotic studied. The results showed a more severe inhibitory effect on microorganisms that were in contact with increases in loads of FLO than those that were in contact with increasing loads of OTC, a condition reflected in the chemical oxygen demand (COD) removal efficiency.

Research on florfenicol residue in coastal area of dalian (northern china) and analysis of functional diversity of the microbial community in marine sediment

An analytical method based on high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) has been developed to investigate florfenicol residues. Among 11 stations, florfenicol was detected in six water samples. The concentrations of florfenicol in the six samples were 64.2 microg L(-1), 390.6 microg L(-1), 1.1 x 10(4) microg L(-1), 29.8 microg L(-1), 61.6 microg L(-1), 34.9 microg L(-1), respectively. These results showed that high levels of florfenicol were observed in water samples collected from stations influenced by aquaculture discharges. However, no florfenicol residue was detected in the sediment samples. Furthermore, the functional diversities of microbial community in four marine sediment samples were analyzed by Biolog microplate. For the sediment samples from the stations where antibacterials had been used, the functional diversity of microbial community was much lower than those from the stations where antibacterials were not used.

Simultaneous determination of residual thiamphenicol and florfenicol in foods of animal origin by HPLC/electrospray ionization-MS/MS

A simple and reliable method using HPLC/MS/MS has been developed for determination of thiamphenicol and florfenicol in foods of animal origin, such as pork, porcine liver, porcine kidney, beef, bovine liver, fish, and chicken. The HPLC separation was performed on a Waters XTerra phenyl column (100 x 2.1 mm, 3.5 microm) with a gradient mobile phase system of 0.1% formic acid-methanol at a flow rate 0.35 ml/min. Negative ionization produced the molecular ions at m/z 354 and 356 for thiamphenicol and florfenicol, respectively. Two characteristic transition reactions (m/z 354-->185, 290 and m/z 356-->336, 185) in the selected reaction monitoring mode were tested for detection and confirmation of thiamphenicol and florfenicol simultaneously. The analytes were extracted with ethyl acetate and defatted with n-hexane by liquid-liquid extraction. The recoveries of thiamphenicol and florfenicol by the developed method were 72.5-97.6%. The limits of determination were 1.0 ng/g (ppb) for both compounds.

Simultaneous determination of florfenicol and its metabolite florfenicol amine in swine muscle tissue by a heterologous enzyme-linked immunosorbent assay

A sensitive and heterologous enzyme-linked immunosorbent assay (ELISA) for the simultaneous detection of florfenicol (FF) and its metabolite florfenicol amine (FFA) in swine muscle tissue was developed. FFA was conjugated to bovine serum albumin by a formaldehyde coupling method as an immunogen to immunize rabbits. FFA, thiamphenicol glycinate, and modified FF were conjugated to ovalbumin as coating antigens. The effect of different types of hapten heterology on the sensitivity and specificity of the ELISA was evaluated. Using FF glutaric anhydride ester as a coating hapten and antibody raised against modified FFA, an ELISA was developed that showed an IC50 value of 0.48 ng/mL. The antibody showed a cross-reactivity of 100% with FFA, 97% with FF, 6% with thiamphenicol, and a negligible value with chloramphenicol. From fortified swine muscle samples at levels of 4-320 ng/g, the average recoveries of FF and FFA ranged from 58.2 to 96.8%, with coefficients of variation less than 14%. Analysis of incurred samples by the ELISA gave similar results to those by a previously developed liquid chromatographic method. The ELISA could be used as a rapid method for the simultaneous determination of FF and FFA in swine muscle tissue.

Assay of florfenicol in swine feed: interlaboratory study

Nuflor (florfenicol) Premix for Swine was recently approved by the U.S. Food and Drug Administration (FDA) for control of swine respiratory disease (SRD). A simple method for the assay of florfenicol in Type C medicated swine feeds was recently evaluated as part of a 4-laboratory study. Florfenicol is extracted from ground feed with acetonitrile-water by shaking and sonication. An Envi-Carb solid-phase extraction cartridge is used to clean up the extract, retaining matrix interferences while allowing florfenicol to elute. The collected eluent is diluted and injected into a reversed-phase liquid chromatographic system. Samples are quantitated by external standard analysis versus multilevel calibration solutions. The procedure is suitable for the quantification of swine feeds in mash or pellet form medicated with 100-300 mg/kg florfenicol. The interlaboratory study was conducted according to Guidance 136 issued by the FDA Center for Veterinary Medicine. The feeds used to evaluate method performance represented different feed compositions (starter and finisher) and manufacturers. The sponsor and 3 independent laboratories obtained mean recoveries (+/-SD) from fortified swine feeds of 100.7% (+/-2.0%), 99.6% (+/-2.8%), 98.8% (+/-1.4%), and 99.3% (+/-1.7%), respectively. Excellent agreement of the results of the assay of blind samples of commercial swine mash and pelleted feeds between laboratories demonstrates that the method is rugged and reproducible.

Determination of florfenicol amine residues in animal edible tissues by an indirect competitive ELISA

Florfenicol (FF) is a broad-spectrum antibiotic used increasingly in aquaculture, livestock, and poultry to treat diseases. To avoid using labor-intensive instrumental methods to detect residues of FF in food and food products, a simple and convenient indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) method for florfenicol's major metabolite, florfenicol amine (FFA), was developed using a polyclonal antibody prepared in this study. FFA was covalently attached to carrier protein as immunogen by using the glutaraldehyde method. The antibodies obtained were characterized by an ELISA method and showed excellent specificity and sensitivity with the 50% inhibition values (IC 50) of 3.34 microg/L for FFA in PBS buffer. In the ELISA, sample extractions were performed by ethyl acetate/ammonium hydroxide (90 + 10, v/v) following combined acid hydrolysis of FF and its known metabolites. The limits of detection (LOD) calculated from the analysis of 20 known negative swine muscle, chicken muscle, and fish samples were 3.08, 3.3, and 3.86 microg/kg (mean + 3 SD), respectively. Recoveries of FFA fortified at the levels of 5, 50, 100, and 300 microg/kg ranged from 64.6 to 124.7%, with coefficients of variation of 11.3-25.8% over the range of FFA concentrations studied. Validation of the ELISA method with FFA-fortified swine muscle at the levels of 10, 50, 100, and 200 microg/kg was carried out using GC, resulting in a similar correlation in swine muscle ( r = 0.97). The results suggest that this ELISA is a specific, accurate, and sensitive method, which is suitable for use as a screening method to detect residues of FFA in animal edible tissues.

Optimization and validation of capillary electrophoretic method for the analysis of amphenicols in poultry tissues

A simple, rapid capillary electrophoretic (CE) method for simultaneous analysis of three amphenicols (chloramphenicol, thiamphenicol and florfenicol) in poultry tissues has been developed and validated. The separation condition were: buffer solution composed with 25 mM sodium tetraborate decahydrate and 10 mM sodium dodecylsulfate, an uncoated fused-silica capillary (57 cm x 75 microm i.d.), voltage 20 kV, and temperature 22 degrees C. The method involved simple deproteinization by acetonitrile and SPE extraction procedure. The analytical method was validated according to the FDA bioanalytical method guidance. The method was linear (r > 0.999) at concentrations ranging from: 0.005 - 1 for chloramphenicol, 0.01 - 1 for thiamphenicol, and 0.025 - 5 microg/g for florfenicol. The precision values were less than 9.8 for intra- and 14.8% for inter-day variability, and accuracies ranged from 92.0 to 106.0% for analyzed amphenicols. The overall recoveries of all antibiotics from tissue samples were above 82.2%. Some new parameters were calculated as limit of decision (CCalpha) and detection capability (CCbeta). The CE method is simple and reliable for simultaneous determination of residues of chloramphenicol, thiamphenicol and florfenicol in muscle with a total run time of less than 7 min.

Residue depletion of florfenicol and its metabolite florfenicol amine in Swine tissues after intramuscular administration

A study of the tissue depletion of florfenicol (FF) administered intramuscularly twice to swine at a dose rate of 20 mg per kg of body weight at 24 h intervals was carried out. Forty healthy cross swine were treated with the FF injection formulation. Five treated animals were selected randomly to be sacrificed at 1, 3, 6, 9, 12, 14, 17, and 21 days withdrawal. FF and florfenicol amine (FFa) residue concentrations in muscle, liver, and kidney were determined using high-performance liquid chromatography (HPLC) with photodiode array (PDA) detection at 225 nm. Liver samples showed the lowest FF and the highest FFa concentrations throughout the experiment period. However, the highest total concentrations of FF and FFa during the study were found in kidney, which indicated that kidney is the target tissue for FF. The sum of FF and FFa concentrations in all tissues analyzed was below the accepted maximum residue limits recommended by the Agriculture Ministry of People's Republic of China and the European Union at 8 days posttreatment.

Simultaneous determination of florfenicol and florfenicol amine in fish, shrimp, and swine muscle by gas chromatography with a microcell electron capture detector

A rapid and sensitive gas chromatography method was developed for the simultaneous determination of florfenicol (FF) and its metabolite florfenicol amine (FFA) in fish, shrimp, and swine muscle. The extracted samples were defatted with hexane and cleaned up by solid-phase extraction using Oasis MCX cartridges. The eluate was evaporated to dryness, and residues were derivatized and determined by gas chromatography with a microcell electron capture detector. Overall average recoveries ranged from 81.7 to 109.7% for fish, 94.1 to 103.4% for shrimp, and 71.5 to 91.4% for swine muscle. The detection limit was 0.5 ng/g for FF and 1 ng/g for FFA, respectively. The method was validated for the determination of incurred swine muscle samples in an actual residue study.

Simultaneous Determination of Chloramphenicol, Thiamphenicol, and Florfenicol Residues in Animal Tissues by Gas Chromatography/Mass Spectrometry

A method was developed for the simultaneous determination of chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FF) residues in animal tissues using gas chromatography/mass spectrometry (GC/MS) with chemical ionization source in negative mode. The homogenized samples were extracted with ethyl acetate and the extracts were partitioned with n-hexane to remove lipids. Further cleanup was performed on a florisil cartridge and the purified samples were derivatized with Sylon BFT [N, O-bis (trimethylsilyl) trifluoroacetamide (BSTFA)-trimethylchlorosilane (TMCS), 99: 1, v/v] in toluene. Meta-nitrochloramphenicol (m-CAP) was used as the internal standard for the determination. Selected ion monitoring (SIM) was used for detection, ions were chosen, respectively, for the monitoring at m/z 432, 466, 468, 470 for m-CAP, m/z 376, 378, 466, 468 for CAP, m/z 409, 411, 499, 501 for TAP, and m/z 339, 341, 429, 431 for FF. Quantitative ions were selected at m/z 466 for CAP and m-CAP, at m/z 339 for FF and at m/z 409 for TAP. The detection limits were 0.03 microg/kg for CAP, 0.2 microg/kg for FF and TAP. The correlation coefficients were above 0.99 for the calibration curves of the medicines. The linear ranges were 0.1 - 8.0 microg/kg for CAP and 0.2 - 4.0 microg/kg for FF and TAP. The reproducibilities of the compounds within a batch were 5.5%, 10.4%, and 8.8% for CAP, FF, and TAP respectively, while the corresponding values between the batches were 7.4%, 20.7%, and 19.1%. The recoveries were 80.0% - 111.5%, and the relative standard deviations were 1.2% - 15.4%. The method is applicable for detection of the residues in animal derived food, such as pork, poultry and aquatic products.

Determination of florfenicol in fish feed by liquid chromatography

A simple, accurate, and reproducible assay was developed for the determination of Florfenicol in medicated fish feed. Florfenicol was extracted from ground feed into an acetonitrile-water mixture by shaking and sonication. A portion of the centrifuged extract was passed through an Envi-Carb solid-phase extraction cartridge, through which Florfenicol eluted unretained. The collected eluant was diluted to adjust for analyte concentration, and injected into a reversed-phase liquid chromatography system. Samples were quantitated by external standard analysis versus multilevel calibration solutions. The procedure is suitable for the quantitation of samples medicated with 0.2-4 g/kg Florfenicol. Accuracy was evaluated by 2 analysts, who determined recovery of Florfenicol from feeds fortified over a range of 0.1-6.0 g/kg. The average recovery was 100.5% (relative standard deviation, 1.2%). The linearity, accuracy, precision, reproducibility (interday and analyst), and selectivity of the method are presented. The detection and quantitation limits were determined to be 0.2 and 1.0 mg/kg, respectively.

[Analysis of chloramphenicol, thiamphenicol and florfenicol in chicken by high performance liquid chromatography with electrospray ionization mass spectrometry]

The method for the analysis of three chloramphenicols including chloramphenicol, thiamphenicol and florfenicol in chickens was developed by high performance liquid chromatography combined with electrospray ionization mass spectrometry (HPLC-ESI-MS-MS). The mass spectrometer was operated in the negative ion mode using multiple reaction monitoring for qualitative and quantitative analysis of these compounds at the same time. Only 1 g of sample was needed, and no solid phase extraction (SPE) procedure was adopted. The advantages of the method are simple operation, less organic chemicals consumed, and shorter operation time. The limits of detection (LOD) were 0.010 microg/kg, and the limits of quantitation (LOQ) were 0.100 microg/kg. The linear plots were obtained between 0.050 and 1.00 microg/L. Overall recoveries were between 69.0% and 92.8% with relative standard deviations between 6.3% and 12.9%.

Optimization and validation of a micellar electrokinetic chromatographic method for the analysis of florfenicol

We have optimized a micellar electrokinetic capillary chromatographic method for the separation of florfenicol and florfenicol amine, its degradation product. The separation was carried out using a 50mM sodium borate buffer (pH 9.0) containing 25mM of sodium dodecyl sulphate. The method selectivity was proven by the simultaneous separation of florfenicol and two structural antibiotics, chloramphenicol and thiamphenicol. The same system can also be applied for the quantitative determination of these antibiotics. The method was then validated regarding linearity, precision and accuracy.

Simultaneous determination of residues of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in farmed aquatic species by liquid chromatography/mass spectrometry

A liquid chromatographic (LC)/mass spectrometric (MS) method was developed for determining the residues of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in a number of aquatic species. The phenicols are extracted with acetone, the extracts are partitioned with dichloromethane, the aqueous layer is removed, and the organic layer is evaporated to dryness. The residue is dissolved in dilute acid and defatted with hexane, and the aqueous layer is prepared for analysis by LC. The phenicols are determined by reversed-phase LC by using a Hypersil C18-BD column with a water-acetonitrile gradient and MS detection using selected-ion recording. Calibration curves were linear for all analytes between 0.015 and 0.425 ng injected. The relative standard deviations for measurements by the proposed method were < 10% for all of the analytes studied, with recoveries ranging from 71% for florfenicol amine to 107% for florfenicol in salmon tissue spiked at the 2 ng/g level. Detection limits of 0.1 ng/g for florfenicol and chloramphenicol, 0.3 ng/g for thiamphenicol, and 1.0 ng/g for florfenicol amine are easily obtainable. The operational errors, interferences, and recoveries for spiked samples compare favorably with those obtained by established LC methodology. The proposed method is simple, rapid, and specific for monitoring residues of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in a number of aquatic species.

Determination of florfenicol amine in channel catfish muscle by liquid chromatography

A method for quantifying florfenicol amine (FFA) in channel catfish muscle was validated according to U.S. Food and Drug Administration guidelines. FFA is the proposed marker residue for the veterinary antibiotic florfenicol in catfish muscle for regulatory surveillance purposes. The method includes acid hydrolysis followed by sample cleanup with ethyl acetate extraction, basification, solid-phase extraction, and quantitation by liquid chromatography with UV detection. The assay was validated at 5 concentrations in the range of 0.075-35 microg/g muscle. The overall mean recovery of FFA from fish tissues fortified at these concentrations ranged from 85.7 to 92.3%, 4.8-17.2% relative standard deviation (RSD). The assay limit of detection was 0.044 microg/g muscle based on analysis of control muscle. Catfish muscle samples containing incurred florfenicol residues were analyzed in quintuplicate with RSD < 5%. Acid hydrolysis has previously been demonstrated to convert florfenicol and its known metabolites to FFA and to release a significant amount of FFA from nonextractable florfenicol residues in tissues containing incurred residues in other species. By using acid hydrolysis, this method should yield a more accurate estimate of the total florfenicol-related residue level in muscle tissue from florfenicol-treated catfish than could be achieved by solvent extraction alone.

Simultaneous determination of residues of chloramphenicol, florfenicol, florfenicol amine, and thiamphenicol in shrimp tissue by gas chromatography with electron capture detection

A gas chromatographic (GC) method is presented for determining residues of chloramphenicol (CAP), florfenicol (FF), florfenicol amine (FFa), and thiamphenicol (TAP) in shrimp tissues, with meta-nitrochloramphenicol (mCAP) as the internal standard. The composited shrimp is extracted with basic ethyl acetate, followed by an acetonitrile-basic ethyl acetate mixture. This extract is centrifuged, filtered, evaporated, and reconstituted in water; the reconstituted extract is acidified, defatted with hexane, and passed through a propylsulfonic acid (PRS) and C18 solid-phase extraction (SPE) system. The C18 SPE column is eluted with methanol, and the PRS SPE column is eluted with basic MeOH plus counter ion. The combined eluates are evaporated, reconstituted in acetonitrile, and derivatized with Sylon BFT. After derivatization, the addition of toluene directly to the sample, followed by the addition of basic water, quenches the derivatization process. After centrifugation, the organic layer is carefully removed, and the analytes are determined by GC with electron capture detection. Shrimp tissues were fortified with fenicols (i.e., CAP, FF, FFa, and TAP) at 5, 10, 20, 40, and 80 ng/mL. Overall recoveries were 88, 101, 91, and 84% with overall interassay (between-day) variabilities (i.e., relative standard deviations) of 5.3, 9.4, 12.8, and 7.4% for CAP, FF, FFa, and TAP, respectively. The method detection limits were calculated as 0.7, 1.4, 2.4, and 1.3 ng/g (ppb) for CAP, FF, FFa, and TAP, respectively, based on a 10 g sample. The quantitation limit as determined empirically by this method is the lower limit of the standard curve, which is about 5 ng/g (ppb) for each analyte.

Simultaneous determination of chloramphenicol, florfenicol, and thiamphenicol residues in milk by gas chromatography with electron capture detection

A gas chromatographic (GC) method is described for determining residues of chloramphenicol (CAP), florfenicol (FF), and thiamphenicol (TAP) in raw milk, with meta-nitrochloramphenicol (mCAP) as internal standard. Milk is extracted with acetonitrile, centrifuged, evaporated, reconstituted in water, and passed through a C18 solid-phase extraction (SPE) column. The SPE column is eluted with 60% methanol, and then the eluate is evaporated and derivatized with Sylon BFT ¿N,O-bis(trimethylsilyl)trifluoroacetamide [BSTFA]-trimethylchlorosilane [TMCS], 99 + 1¿. After derivatization, toluene is added directly to the sample, followed by water, to quench the derivatization process. After centrifugation, the organic layer is carefully removed. Analytes are determined by GC with electron capture detection (ECD). Milk was fortified with fenicols (the collective name for CAP, FF, and TAP) at 5, 10, 20, 40 and 80 ng/mL (target level = 10 ng/mL). Overall recoveries were 92, 100, and 104% for CAP, FF, and TAP, respectively. Overall interassay (between-day) variabilities were 6.1, 6.7, and 6.0% for CAP, FF, and TAP, respectively. Raw milk samples containing incurred residues of FF were also analyzed.

Simultaneous determination of residues of florfenicol and the metabolite florfenicol amine in fish tissues by high-performance liquid chromatography

A simple and rapid high-performance liquid chromatographic method for the simultaneous extraction and determination of residues of florfenicol and its metabolite florfenicol amine in fish tissue, muscle and liver has been developed. The calibration curves were linear, the recovery of florfenicol was 99-107%, and the recovery of florfenicol amine was 94-100%. The detection limits for florfenicol and florfenicol amine were 20 ng/g in muscle and 50 ng/g in liver.

Determination of thiamphenicol residues in chicken muscles by column liquid chromatography

A column liquid chromatographic (CLC) method for the determination of thiamphenicol residues in chicken muscles was developed. The drug is extracted from minced muscles with ethyl acetate and the extract is evaporated to dryness. The residue is dissolved in 10% sodium chloride solution and partitioned with n-hexane. Thiamphenicol is extracted with ethyl acetate and, after evaporation of the solvent, the residue is cleaned up by alumina column chromatography. CLC analysis is carried out on a Nucleosil C18 column with ultraviolet detection of thiamphenicol at 230 nm. The average recoveries of thiamphenicol added to muscles at 0.2 and 0.1 ppm were 92.8 and 90.0%, respectively. The detection limit was 5 ng for thiamphenicol standard, which corresponds to 0.05 ppm in muscles.

Reversed-phase liquid chromatographic separation of enantiomeric and diastereomeric bases related to chloramphenicol and thiamphenicol

The important antimicrobial agents chloramphenicol and thiamphenicol are N-acylated amines whose chemical structures include two chiral centers. Each drug is the single enantiomer of R,R configuration. The N-deacylated bases of the drugs are important intermediates in their synthesis and optical resolution. In this report, reversed-phase HPLC methods are described for the separation of enantiomeric and diastereomeric bases of the two drugs and of two closely related bases used in some syntheses of the drugs. The stereoisomeric bases were derivatized with a homochiral isothiocyanate and the resulting diastereomeric thioureas were separated on C18 columns with methanol:water mixtures as mobile phases and detection at 254 nm. The four stereoisomeric bases of chloramphenicol and those of its unnitrated analogue were thus separable after derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate. This reagent also allowed the separation of the D-threo isomer of the p-mercaptomethyl analogue of thiamphenicol base from its stereoisomers. The stereoisomers of thiamphenicol base were similarly separated with (R)-alpha-methylbenzyl isothiocyanate as the derivatizing agent. The diastereomers of chloramphenicol base and of thiamphenicol base were chromatographically separable after derivatization with the nonchiral reagent benzyl isothiocyanate. The procedures developed may be useful in the determination of the stereoisomeric composition of the drugs in research and in quality control, and may be applicable to other similar agents whose chemistry and pharmacology are receiving considerable attention.