Determination of chloramphenicol residues in animal feeds by liquid chromatography with photo-diode array detection

Mixture toxicity effects of chloramphenicol, thiamphenicol, florfenicol in Daphnia magna under different temperatures

Acute toxicities of chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FLO) and their mixtures on Daphnia magna under two representative temperatures of the aquatic environment (20 and 25 °C) have been examined. Their toxicities depicted with an order of 72-h EC₅₀ values were as follows: CAP > FLO > TAP and CAP ≈ FLO > TAP under 20 and 25 °C, separately. Furthermore, the acute toxicity significantly increased with the rise of temperature from 20 to 25 °C in nearly all separate and mixture phenicol antibiotics. Meanwhile, the most toxic combination under two different temperatures was diverse. The nature of toxicological interactions of phenicol antibiotic mixtures was analyzed by Combination Index (CI) equation. In general, a dual synergism-antagonism effect was dominant in nearly all mixtures at both temperatures. The prediction suitability of Concentration Addition (CA), Independent Action (IA) models, and CI method was compared, suggesting that the CI equation seems to be more appropriate for predicting the toxicity values of phenicol drugs than CA and IA models. In brief, phenicol antibiotic mixtures with temperature variation may pose more significant hazards and risks to aquatic organisms; hence, the environment.

Evaluation of the subtle effects and oxidative stress response of chloramphenicol, thiamphenicol, and florfenicol in Daphnia magna

Phenicol antibiotics, such as chloramphenicol, thiamphenicol, and florfenicol, are commonly used in the veterinary and aquaculture fields to treat diseases and have frequently been detected in aquatic environments. Nevertheless, there is limited information regarding the effects of phenicol antibiotics on aquatic nontarget species. Thus, the present study aims to investigate the long-term (21-d) influence on the reproduction and growth of and the acute (24-h) oxidative response and tissue damage in the crustacean Daphnia magna after exposure to phenicol drugs, including their environmental concentrations. The results indicate that D. magna exposed to florfenicol are likely to cause more adverse effects than those exposed to chloramphenicol and thiamphenicol over long-term (21-d) exposures. Furthermore, changes in biochemical biomarkers such as malondialdehyde (MDA), catalase (CAT), and reduced glutathione (GSH) induced by individual and mixtures of phenicol antibiotics were also observed. Low concentrations of chloramphenicol, thiamphenicol + florfenicol, and chloramphenicol + thiamphenicol significantly increased the MDA levels of D. magna after 24-h exposures, causing cellular oxidative damage in the animals. In addition, discrepancies between CAT activities and GSH levels were observed, underscoring the need to evaluate multiple indicators of oxidative stress in toxicological studies using D. magna as a model. Environ Toxicol Chem 2019;38:575-584. © 2018 SETAC.

Magnetic molecularly imprinted polymer prepared by microwave heating for confirmatory determination of chloramphenicol in chicken feed using high-performance liquid chromatography-tandem mass spectrometry

A magnetic molecularly imprinted polymer (MMIP) for chloramphenicol was prepared using a surface-imprinted and microwave-heating-induced polymerization method. The surfaces of the magnetic particles were first double-bond functionalized with 3-(trimethoxysilyl)propyl methacrylate (γ-MPS), followed by the copolymerization of 4-vinyl pyridine (4-VP) and trimethylolpropane trimethacrylate (TRIM) in the presence of chloramphenicol as a template and 1,1-azobis(cyclohexane-carbonitrile) (ABCN) as an initiator in a mixture of dimethyl sulfoxide and water with microwave heating at 80°C. The magnetic polymer possesses supraparamagnetic properties and was used to concentrate and cleanup chicken feed extract, followed by chromatographic separation using a Lichrospher®100 RP C8 column and detection with two multi-reaction monitoring transitions at m/z 321→ 152 and m/z 321→ 257. The mean recoveries obtained at two spiking levels were in the range of 94.6-100% The relative intra- and inter-day standard deviations were in the range of 1.4-2.6% and 5.1-5.7%, respectively. The detection limit of the method was 0.12 µg kg^-1. This confirmatory method was successfully applied to determine chloramphenicol in chicken feed samples.

Label-free and sensitive aptasensor based on dendritic gold nanostructures on functionalized SBA-15 for determination of chloramphenicol

A highly sensitive and low-cost electrochemical aptasensor was developed for the determination of chloramphenicol (CAP). The system was based on a CAP-binding aptamer, a molecular recognition element, and 1,4-diazabicyclo[2.2.2]octane (DABCO)-supported mesoporous silica SBA-15 on the surface of a screen-printed graphite electrode for formation of dendritic gold nanostructures and improving the performance and conductivity of the biosensor. Hemin has been applied as an electrochemical indicator which interacted with the guanine bases of the aptamer. In the absence of CAP, hemin binds to the aptamer and produces a weak differential pulse voltammetric (DPV) signal. The presence of CAP led to stabilization of the folded aptamer, which generated an amplified DPV signal. The peak current of hemin increased linearly with the concentration of CAP. Under optimal conditions, two linear ranges were obtained from 0.03 to 0.15 μM and 0.15 to 7.0 μM, respectively, and the detection limit was 4.0 nM. The prepared biosensor has good selectivity against other non-target drugs. Thus, the sensor could provide a promising platform for the fabrication of aptasensors. The feasibility of using this aptasensor was demonstrated by determination of CAP in a human blood serum sample.

Fluorescence quenching for chloramphenicol detection in milk based on protein-stabilized Au nanoclusters

In the present study, we report a simple and rapid method for sensitive and selective determination of chloramphenicol (CAP) based on fluorescence of bovine serum albumin-stabilized Au nanoclusters (BSA-AuNCs). The BSA-AuNCs exhibit strong red emission. Upon addition of CAP to BSA-AuNCs, the fluorescence intensity of AuNCs shows a dramatic decrease attributing to the photo-induced electron transfer process from the electrostatically attached CAP to the BSA-AuNCs. The effects of pH, amount of BSA-AuNCs, temperature and reaction time on the detection of chloramphenicol were investigated. Under the optimal conditions, trace amounts of CAP could be detected. The linear working range is 0.10-70.00 μM with a detection limit 33 nM (S/N=3). In addition, the proposed method has been successfully applied to the detection of CAP in milk samples and largely improves the application of spectral method for quantitative analysis of CAP.

Determination of chloramphenicol, enrofloxacin and 29 pesticides residues in bovine milk by liquid chromatography-tandem mass spectrometry

A sensitive method for determination of chloramphenicol, enrofloxacin and 29 pesticides residues in bovine milk by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed. Residues of the targets were extracted from milk with acetonitrile, cleaned up by C(18)-SPE cartridge, and then determined by HPLC-MS/MS. The MS detection was operated in positive or negative ionization mode, depending on the compounds. For confirmation of each target compound, two precursor ion>product ion transitions were selected by multi-reaction monitoring mode (MRM). The method showed good linearity for all the tested compounds over the studied concentration range with correlation coefficient higher than 0.9910. Recoveries for the studied compounds at three spiked levels (0.05, 0.10, 0.19mgkg(-1)) in bovine milk were in the range of 71-107% with RSDs not larger than 13.7%, except that recoveries of trifluralin ranged between 62% and 70% at the spiked levels. Limits of quantitation for the analytes were estimated to range between 0.03×10(-3) and 14.5×10(-3)mgkg(-1). The proposed method was applied for the determination of the analytes residues in real samples. The found levels of the analytes in milk samples were lower than maximum residues levels (MRL).

Development and validation of a rapid multi-class method for the confirmation of fourteen prohibited medicinal additives in pig and poultry compound feed by liquid chromatography-tandem mass spectrometry

A confirmatory method has been developed to allow for the analysis of fourteen prohibited medicinal additives in pig and poultry compound feed. These compounds are prohibited for use as feed additives although some are still authorised for use in medicated feed. Feed samples are extracted by acetonitrile with addition of sodium sulfate. The extracts undergo a hexane wash to aid with sample purification. The extracts are then evaporated to dryness and reconstituted in initial mobile phase. The samples undergo an ultracentrifugation step prior to injection onto the LC-MS/MS system and are analysed in a run time of 26 min. The LC-MS/MS system is run in MRM mode with both positive and negative electrospray ionisation. The method was validated over three days and is capable of quantitatively analysing for metronidazole, dimetridazole, ronidazole, ipronidazole, chloramphenicol, sulfamethazine, dinitolimide, ethopabate, carbadox and clopidol. The method is also capable of qualitatively analysing for sulfadiazine, tylosin, virginiamycin and avilamycin. A level of 100 microg kg(-1) was used for validation purposes and the method is capable of analysing to this level for all the compounds. Validation criteria of trueness, precision, repeatability and reproducibility along with measurement uncertainty are calculated for all analytes.

The occurrence of chloramphenicol and tetracyclines in municipal sewage and the Nanming River, Guiyang City, China

The occurrence of antibiotics including chloramphenciol (CAP), oxytetracycline (OTC) and tetracycline (TC) was studied in municipal sewage, river water and sediment. Temporal and spatial variations of antibiotic concentrations in municipal sewage, river water and sediment were evaluated. In municipal sewage, CAP, OTC and TC concentrations were in the range of 5.8-47.4, 0.16-5.7 and 0.7-65.2 microg L(-1), respectively, and showed a temporal variation with high antibiotic concentrations appearing in the cold season. Untreated municipal sewage can seriously influence both river water and sediment. Generally, high antibiotic concentrations in river water appeared in winter owing to the low flow condition as well as the high antibiotic concentration in the sewage. However, high CAP and OTC concentrations in sediment were observed in summer most likely because runoff in high flow season can carry wastes from some origins (e.g. livestock farms in the countryside) into the river. The partitioning of antibiotics in river water and sediment suggests a lower sorption of TCs to the sediment compared to previous studies, which is believed to be caused by the high Ca2+ and Mg2+ concentrations, ionic strength and pH of the river water in the carbonate area.

Chromatographic analysis of banned antibacterial growth promoters in animal feed

The issue of antimicrobial use in animals used as food is of global concern. Antimicrobials are used in animal agriculture to improve health and welfare of animals, meat quality, the economic efficiency of growth and production and public health by decreasing shedding of zoonotic pathogens. However, large quantities are often used without professional supervision. The growth-promotant (now reclassified as zootechnical feed additives) effect of low levels of antibiotics in animal feeds was first described in the late 1940s. Already in 1969 the Swann Committee recommended that use of antibiotics as a supplement in animal feedstuff should be restricted to those with little or no application as therapeutic agents for humans and animals, which would not impair the efficacy of therapeutic antibiotics through the development of resistant strains of organisms. Antimicrobials like avoparcin, ardacin, zinc bacitracin, virginiamycin, tylosin, spriramycin, carbadox and olaquindox were withdrawn within the period 1997-1999. Four others (monensin sodium, salinomycin sodium, avilamycin and flavophospholipol) were still permitted for use as growth promoters in animal feed to animals marketed in the European Union (EU). Since January 2006, they have been banned as well. This review focuses on the analytical methods developed to be an effective tool for monitoring compliance with the ban.