Analysis of quinolone residues in edible animal products

Colloidal SERS measurement of enrofloxacin with petaloid nanostructure clusters formed by terminal deoxynucleotidyl transferase catalyzed cytosine-constituted ssDNA

We developed petal-like plasmonic nanoparticle (PLNP) clusters-based colloidal SERS method for enrofloxacin (EnFX) detection. PLNPs were synthesized by the regulation of single-stranded DNA composed of homo-cytosine deoxynucleotides (hC) catalyzed by terminal deoxynucleotidyl transferase. SERS hot spots were created via the agglomeration process of PLNPs by adding an inorganic salt potassium iodide solution, in which EnFX molecules were attached to the negatively charged PLNPs surface by electrostatic interactions. This approach enabled direct in situ detection of antibiotic residues, achieving a limit of detection (LOD) of 1.15 μg/kg for EnFX. The spiked recoveries of the SERS method were approximately 92.7% to 107.2% and the RSDs ranged from 1.05% to 7.8%, indicating that the method can be applied to actual sample detection. This colloidal SERS measurement platform would be very promising in various applications, especially in real-time and on-site food safety screening owing to its rapidness, simplicity, and sensitivity.

Multiresidue Determination of 26 Quinolones in Poultry Feathers Using UPLC-MS/MS and Their Application in Residue Monitoring

As a non-traditional sample matrix, feather samples can be used to effectively monitor antibiotic addition and organismal residue levels in poultry feeding. Therefore, an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to simultaneously determine the residue levels of 26 quinolones in poultry feathers. The feather samples were extracted by sonication with a 1% formic acid and acetonitrile mixture in a water bath at 50 °C for 30 min, purified by the adsorption of multiple matrix impurities, dried with nitrogen, redissolved, and analyzed by UPLC-MS/MS. The linearity, limit of detection (LOD), limit of quantification (LOQ), recovery and precision were calculated. The 26 antibiotics demonstrated good linearity in the linear range. The recoveries and coefficients of variation were 78.9-110% and <13.7% at standard spiked levels of 10, 100 and 200 μg/kg, respectively. The LOD and LOQ were 0.12-1.31 and 0.96-2.60 μg/kg, respectively. The method also successfully identified quinolone residues in 50 poultry feather samples. The results showed that quinolones can accumulate and stabilize for a certain period of time after transferring from the body to the feathers of poultry.

Ionic liquid-based dispersive liquid-liquid microextraction followed by magnetic solid-phase extraction for determination of quinolones

An ionic liquid-based dispersive liquid-liquid microextraction (IL-DLLME) combined with magnetic solid-phase extraction (MSPE) was developed for extraction of quinolones (quinolones) from honey and milk prior to high-performance liquid chromatography (HPLC) analysis. 1-Butyl-3-methylimidazolium hexafluorophosphate was used as the extraction solvent and an effective adsorbent based on chitosan modified magnetic core-shell functionalized multi-walled carbon nanotube (MWCNTs-Fe₃O₄@SiO₂-CS) nanoparticles was used to assist IL to adsorb quinolone residues in honey and milk samples. Extraction conditions were optimized through one-factor-at-a-time and response surface methodology using a Box-Behnken design. Under optimum conditions satisfactory linearity (R² > 0.999) and high sensitivity (method limits of quantification were 4-8 μg kg^-1 or μg L^-1 in honey or milk samples) was achieved. The recoveries of quinolones in honey and milk ranged from 81.2 to 109%. Based on this study, the proposed method was employed for the determination of antibiotic residues in honey and milk samples.

Tea polyphenols and Levofloxacin alleviate the lung injury of hepatopulmonary syndrome in common bile duct ligation rats through Endotoxin -TNF signaling

BACKGROUND & AIMS

Hepatopulmonary syndrome (HPS) is characterized by pulmonary vasodilation and arterial blood oxygen desaturation in patients with chronic liver disease. Generally, common bile duct ligation (CBDL) rats are a suitable experimental model for studying hepatopulmonary syndrome. Our previous study demonstrated that endotoxin surges markedly, followed by bacterial translocation and the loss of liver immune function in all the stages of CBDL, thereby contributing to the pathogenesis of HPS. However, the mechanisms behind the increase of the endotoxin and how to alleviate it have not yet been elucidated. Pulmonary injury induced by increased bilirubin, endotoxin, and inflammatory mediators occurs in the early and later stages of CBDL. This study assessed the effects of Tea polyphenols (TP) and Levofloxacin on endotoxin reduction and suppression of lung injury in HPS rats in the long and short term, respectively.

METHODS

Morphological change of pulmonary injury, HPS relative index, endotoxin concentration, and the activation extent of Malondialdehyde (MDA) and Myeloperoxidase (MPO) were evaluated in CBDL rats with or without TP and Levofloxacin for three weeks or six weeks. The inflammation factors of serum, lung tissue, and BALF were then compared at the same condition for the two time periods. This was followed by adoption of the network pharmacology approach, which was mainly composed of active component gathering, target prediction, HPS gene collection, network analysis, and gene enrichment analysis. Finally, the mRNA and protein levels of the inflammatory factors were studied and relative signaling expression was assessed using RT-PCR and Western blot analysis.

RESULTS

The obtained results indicated that the pulmonary injury manifestation was perceived and endotoxin, MDA, and MPO activation were markedly increased in the early and later stages of CBDL. TP and Levofloxacin treatment alleviated endotoxin infection and inflammation factor expression three weeks and six weeks after CBDL. In addition, Levofloxacin displayed a short time anti-bacterial effect, while TP exerted a long period function. TP and Levofloxacin also reduced TNF-α, TGF-β, IL-1β, PDGF-BB, NO, ICAM-1, and ET-1 expression on the mRNA or protein expression. With regard to the pharmacological mechanism, the network analysis indicated that 12 targets might be the therapeutic targets of TP and Levofloxacin on HPS, namely ET-1, NOs3, VEGFa, CCl2, TNF, Ptgs2, Hmox1, Alb, Ace, Cav1, and Mmp9. The gene enrichment analysis implied that TP and Levofloxacin probably benefited patients with HPS by modulating pathways associated with the AGE-RAGE signaling pathway, the TNF signaling pathway, the HIF-1 signaling pathway, the VEGF signaling pathway, and the IL-17 signaling pathway, Rheumatoid arthritis, Fluid shear stress, and atherosclerosis. Finally, the TNF-α level was mainly diminished on the protein level following CBDL.

CONCLUSIONS

TP and Levofloxacin could alleviate pulmonary injury for short and long period, respectively, while at the same time preventing endotoxin and the development of HPS in CBDL rats. These effects are possibly associated with the regulation of the Endotoxin -TNF-α pathways.

Immunoassays on thiol-ene synthetic paper generate a superior fluorescence signal

The fluorescence-based detection of biological complexes on solid substrates is widely used in microarrays and lateral flow tests. Here, we investigate thiol-ene micropillar scaffold sheets ("synthetic paper") as the solid substrate in such assays. Compared to state-of-the-art glass and nitrocellulose substrates, assays on synthetic paper provide a stronger fluorescence signal, similar or better reproducibility, lower limit of detection (LOD), and the possibility of working with lower immunoreagent concentrations. Using synthetic paper, we detected the antibiotic enrofloxacin in whole milk with a LOD of 1.64 nM, which is on par or better than the values obtained with other common tests, and much lower than the maximum level allowed by European Union regulations. The significance of these results lays in that they indicate that synthetically-derived microstructured substrate materials have the potential to improve the performance of diagnostic assays.

Collection and Separation of Fleroxacin and Ciprofloxacin in Ultrasound-Assisted Ionic Liquid Salting-Out Microextraction System

An ultrasound-assisted ionic liquid (IL) salting-out microextraction system was developed and applied for the extraction of quinolone antibiotics from urine. A precipitate was formed from the salt and IL, and it acted as the sorbent for the analytes. The precipitate containing the analyte was separated by filtration, redissolved, and the solution then was evaporated. The resulting extract was redissolved for high-performance liquid chromatographic analysis. Several parameters, including type and volume of IL, the type and amount of salts, sample pH, temperature and extraction time were optimized. Under the optimal experimental conditions, the limits of detection for fleroxacin and ciprofloxacin were 3.12 and 4.97 μg L-1, respectively. When the present method was applied to real urine sample analysis, the analyte recoveries ranged from 82.3 to 106.8%. This ultrasound-assisted IL salting-out microextraction system had the characteristics of high recoveries, shorter separation time and easy-to-perform collection procedure, which yielded the method to have potential for wide application.

Direct injection Fourier transform ion cyclotron resonance mass spectrometric method for high throughput quantification of quinolones in poultry

Many recent studies have shown high detection frequencies of quinolone antibiotics in poultry, as well as an increasing incidence of antimicrobial resistance. The main purpose of this project was to develop a fast and reliable analytical method for the detection of quinolones in poultry meat. In order to develop a rapid quantitative confirmation method, ion cyclotron resonance mass spectrometer was used. First, the sample preparation procedure was simplified by reducing the procedure to extraction and freezing out steps. Second, the chromatographic separation step was excluded and mass spectrometric parameters were optimised. Third, the method was validated by fortifying a blank matrix at four levels (0.5, 1, 1.5, and 2 times the maximum residue limit (MRL) or level of interest in those cases when no MRL was established). As a result, the overall analysis time was reduced to less than an hour. The validation study revealed that the method is capable of detection and confirmation of ten quinolone compounds in poultry above the detection capability (CCβ) of the procedure. Finally, the developed method was applied to 19 commercially available chicken meat samples. None of the samples contained quinolones above the limit of quantification (LOQ) of the method. Analysis of treated chickens revealed that the developed method is suitable for the determination of ciprofloxacin and enrofloxacin. The developed method could be one of the fastest quantitative confirmatory methods for the analysis of quinolones available so far.

Separation and determination of ciprofloxacin in seawater, human blood plasma and tablet samples using molecularly imprinted polymer pipette-tip solid phase extraction and its optimization by response surface methodology

By synthesizing a molecular imprinted polymer as an efficient adsorbent, ciprofloxacin was micro-extracted from seawater, human blood plasma and tablet samples by pipette-tip micro solid phase extraction and determined spectrophotometrically. Response surface methodology was applied with central composite design to build a model based on factors affecting on microextraction of ciprofloxacin; including volume of eluent solvent, number of extraction cycles, number of elution cycles, and pH of sample. Other factors that affect extraction efficiency, such as type of eluent solvent, volume of sample, type, and amount of salt were optimized with one-variable-at-a-time method. Under optimum extraction condition, pH of sample solution was 7.0, volume of eluent solvent (methanol) was 200 µL, volume of sample solution was 10 mL, and the number of extraction and elution cycles was five and seven, respectively, amount of Na₂ SO₄ (as salt) and MIP (as sorbent) were optimized at 150 and 2 mg, respectively. The linear range of the suggested method under optimum extraction factors was 5-150 µg/L with a limit of detection of 1.50 µg/L for the analyte. Reproducibility of the method (as relative standard deviation) was better than 7%.

A convenient fluorescent assay for quinolones based on their inhibition towards the oxidase-like activity of Cu2+

This work reports on a novel and convenient fluorescent assay for four quinolones including nalidixic acid, cinoxacin, ciprofloxacin and moxifloxacin, with Cu²⁺-triggered and quinolone-inhibited oxidation of o-phenylenediamine.

Sequential injection analysis for the determination of fluoroquinolone antibacterial drug residues by using eosin Y as complexing agent

A sequential injection analysis (SIA) method was developed for the rapid and sensitive determination of fluoroquinolone residues, including norfloxacin, ciprofloxacin and enrofloxacin, in fish samples. The method is based on the reaction between fluoroquinolone drug and eosin Y in Britton-Robinson buffer (pH 2.0), forming pink colored complexs with maximum absorptions at 522, 525 and 527 nm for norfloxacin, ciprofloxacin and enrofloxacin, respectively. Linearity ranges were found to be 0.05-10.0 mg L^-1 (r² = 0.9996), 0.1-10.0 mg L^-1 (r² = 0.9995) and 0.05-10.0 mg L^-1 (r² = 0.9997) for norfloxacin, ciprofloxacin and enrofloxacin, respectively. The detection limit was found to be in the range of 0.013-0.019 mg L^-1. The method was tested and validated for various parameters according to main guidelines. The proposed SIA method was successfully applied for the determination of fluoroquinolone drug residues in fish samples with the sampling rate of 47 h^-1. The results demonstrated that the method is accurate, precise and reproducible, while being simple, rapid, economical and less time consuming. It can be suitably applied for the estimation of fluoroquinolone drug residues in routine quality control.

Detection and Quantitation of Lomefloxacin and Pefloxacin Residues in the Organ Tissues and Eggs of Laying Hens

Lomefloxacin (LOM) and pefloxacin (PEF) are synthetic antibiotics that have been used in the treatment of infectious diseases in both human and animals. In the People's Republic of China, the use of LOM and PEF in livestock has been prohibited because of the concern that the residues of these drugs may pose a risk to public health. Despite this prohibition, these drugs are still being used in the poultry industry illegally, and so far there has been no systematic study of the persistence of LOM and PEF residues in chickens. In this study, laying hens were treated with a daily dose (10 mg/kg of body weight) of LOM or PEF for five consecutive days, and the drug residues in various tissues and eggs were determined over a 15-day period after the last drug administration. The highest LOM and PEF residual concentrations were found in the tissues 4 h after the last drug administration, and concentrations gradually decreased over time. Plasma had the lowest and liver had the highest residual concentrations throughout the 15-day study period. At the end of the 15 days, 3.64 ± 0.74 μg/kg LOM and 1.78 ± 0.28 μg/kg PEF were detected in the liver, with slightly lower residual concentrations in the kidney. No LOM or PEF residue was detected in the ovarian follicle, plasma, and muscle at the end of the 15 days. In eggs, the depletion rate of LOM was slower than that of PEF. LOM and PEF residues were detected in whole eggs for up to 10 and 8 days, respectively, after drug administration ceased. These findings suggest that the liver and, to a lesser extent, the kidney may be the sites where LOM or PEF residues would persist. This information can be a reliable reference for governmental agencies with respect to the screening of LOM and PEF residues in food products derived from laying hens.

Determination and health risk assessment of enrofloxacin, flumequine and sulfamethoxazole in imported Pangasius catfish products in Thailand

The goals of this study were to determine the levels of three antibiotics - enrofloxacin, flumequine and sulfamethoxazole - in Pangasius catfish products imported into Thailand and to assess the health risks from consumption. To extract these antibiotic residues, acetonitrile, methanol and a small amount of formic acid were used as solvents. Determination of the antibiotics after extraction steps was carried out by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) technique. The results showed that 14 and 3 samples of Pangasius catfish products were contaminated with enrofloxacin and sulfamethoxazole, respectively. No flumequine residue was found. While the concentration levels of these antibiotics in most contaminated samples were lower than the European Union (EU) standard, one sample was found to contain sulfamethoxazole at 245.91 µg kg^-1, which was higher than the EU standard (100 µg kg^-1), indicating the likelihood that some contaminated freshwater fish products are widely distributed in Thai markets. Notably, the concentration levels of enrofloxacin in samples of Pangasius catfish with skin were higher than in non-skin products, suggesting that products with skin might retain more antibiotic residues than non-skin products. Although the hazard quotient showed that consuming imported Pangasius catfish products, based on the current consumption rate, will not adversely affect consumer health, antibiotic residues in Pangasius catfish products imported into Thailand should be continually monitored.

Four Specific Hapten Conformations Dominating Antibody Specificity: Quantitative Structure-Activity Relationship Analysis for Quinolone Immunoassay

Antibody-based immunoassay methods have been important tools for monitoring drug residues in animal foods. However, because of limited knowledge about the quantitative structure-activity relationships between a hapten and its resultant antibody specificity, antibody production with the desired specificity is still a huge challenge. In this study, the three-dimensional quantitative structure-activity relationship (3D QSAR) was analyzed in accordance with the cross-reactivity of quinolone drugs reacting with the antibody raised by pipemidic acid as the immunizing hapten and compared with the reported cross-reactivity data and their hapten structures. It was found that the specificity of a quinolone antibody was strongly related to the conformation of the hapten used and that hapten conformations shaped like the letters "I", "P", and "Φ" were essential for the desired high specificity with low cross-reactivity, but that the hapten conformation shaped like the letter "Y" led to an antibody with broad specificity and high cross-reactivity. Almost all of the antibodies against quinolones could result from these four hapten conformations. It was first found that the concrete conformations dominated the specificity of the antibody to quinolone, which will be of significance for the accurate hapten design, predictable antibody specificity, and better understanding the recognition mechanism between haptens and the antibodies for immunoassays.

Simultaneous determination of chlortetracycline, ampicillin and sarafloxacin in milk using capillary electrophoresis with electrochemiluminescence detection

A fast, inexpensive and sensitive approach for the simultaneous determination of chlortetracycline, ampicilline and sarafloxacin in milk was developed using capillary electrophoresis coupled with an electrochemiluminescence detector. Under the optimal detection conditions, the linear ranges for chlortetracyline, ampicilline and sarafloxacin were 0.030-5.0, 0.050-5.0 and 0.0040-2.0 μg ml^-1, respectively. The correlation coefficients of chlortetracycline, ampicilline and sarafloxacin were determined as 0.9997, 0.9952 and 0.9978, respectively. Detection limits (S/N = 3) of chlortetracycline, ampicilline and sarafloxacin were found as 0.017, 0.018 and 0.0013 μg ml^-1, respectively. This method was successfully applied for the determination of chlortetracycline, ampicilline and sarafloxacin in milk. The recoveries were between 95.3% and 100%. The relative standard deviations of the detection limit and recovery were less than 2.6% and 3.2%, respectively.

Wildlife contamination with fluoroquinolones from livestock: Widespread occurrence of enrofloxacin and marbofloxacin in vultures

There is much recent interest in the presence and impact of veterinary pharmaceuticals in wildlife. Livestock carcasses are often disposed of in supplementary feeding stations for avian scavengers, as a management and conservation tool for these species worldwide. In feeding stations, vultures and other scavengers can consume carcasses almost immediately after disposal, which implies the potential ingestion of veterinary pharmaceuticals as a non-target consequence of supplementary feeding. Using UPLC-MS/MS and HPLC-TOF, we evaluated the presence and concentration of fluoroquinolone residues in plasma of nestling vultures feeding on domestic livestock carrion. Three different fluoroquinolones (marbofloxacin, enrofloxacin and its metabolite ciprofloxacin) and a non-targeted β-lactam (nafcillin) were detected in vulture plasma. The high proportion of individuals (92%) with fluoroquinolone residues at variable concentrations (up to ∼20 μg L(-1) of enrofloxacin and ∼150 μg L(-1) of marbofloxacin) sampled in several geographically distant colonies and on different dates suggests that these and other drugs were potentially ingested throughout nestling development. Contamination with veterinary fluoroquinolones and other pharmaceuticals should be considered as an unintended but alarming consequence of food management in threatened wildlife.

5-Sulfosalicylic acid dihydrate-based pretreatment for the modification of enzyme-linked immunoassay of fluoroquinolones in fishery products

A simple, rapid sample extraction method for the determination of FQs was developed. Fishery samples were extracted with 2% of 5-sulfosalicylic acid dihydrate and the extracts were analyzed directly without any further purification or clean-up procedures. The FQs were determined with standards of 2% of 5-sulfosalicylic acid dihydrate in the concentration range of 0.1-25.6 μg L(-1), and the limit of detection (LOD) was 0.1 μg L(-1). The matrix interference originated from fishery samples was eliminated by 2% of 5-sulfosalicylic acid dihydrate and did not interact with horseradish peroxidase (HRP) labeled IgG in western blotting. No significant matrix interference was observed as samples extracted with 2% of 5-sulfosalicylic acid dihydrate. Recoveries of FQs in fishery muscle were between 72.37-94.35% in the concentrations range of 10-50 μg kg(-1).This extraction procedure was much rapider and simpler to conventional ELISA extraction procedure and could be used as a time-saving and cost-effective method for FQs monitoring in fishery samples.

Decay mechanisms of protonated 4-quinolone antibiotics after electrospray ionization and ion activation

This study presents a detailed experimental investigation of charge isomers of protonated 4-quinolone antibiotics molecules formed during electrospray ionization (ESI) with proposed dissociation mechanisms after collisional activation. Piperazinyl quinolones have been previously shown to exhibit erratic behavior during tandem MS analyses of biological samples, which originated from varying ratios of two isomeric variants formed during ESI. Here, a combination of ESI-collision-induced dissociation (CID), differential ion mobility spectrometry (DMS), high resolution MS, and density functional theory (DFT) was used to investigate the underlying mechanisms of isomer formation and their individual dissociation behaviors. The study focused on ciprofloxacin; major findings were confirmed using structurally related 4-quinolones. DFT calculations showed a reversal of basicity for piperazinyl quinolones between liquid and gas phase. We provide an experimental comparison and theoretical treatment of factors influencing the formation ratio of the charge isomers during ESI, including solvent pH, protic/aprotic nature of solvent, and structural effects such as pK a and proton affinity. The actual dissociation mechanisms of the isomers of the protonated molecules were studied by separating the individual isomers via DMS-MS, which allowed type-specific CID spectra to be recorded. Both primary CID reactions of the two charge isomers originated from the same carboxyl group by charge-remote (CO(2) loss) and charge-mediated (H(2)O loss) fragmentation of the piperazinyl quinolones, depending on whether the proton resides on the more basic keto or the piperazinyl group, followed by a number of secondary dissociation reactions. The proposed mechanisms were supported by calculated energies of precursors, transition states, and products for competing pathways.

Development of sensitive and reliable LC-MS/MS methods for the determination of three fluoroquinolones in water and fish tissue samples and preliminary environmental risk assessment of their presence in two rivers in northern Poland

Antibiotic consumption (e.g. fluoroquinolones (FQs)) and, as a consequence, their presence in the environment, have received a lot of attention in the last several years due to increasing numbers of diseases and infections that are becoming resistant to traditional treatments for both humans and animals. In addition, even though antibiotics are safe for human and veterinary usage, ecosystems may be exposed to these substances. In this study, analytical methods for determining enrofloxacin (ENR), norfloxacin (NOR) and ciprofloxacin (CIP) in water samples and fish tissue based on the LC-MS/MS technique were developed and validated. As there is no data available concerning the risks posed by antibiotics in Poland, the proposed methods were applied for monitoring drug presence in environmental samples collected from two rivers in northern Poland. Evaluations of the ecotoxicity of ENR, NOR and CIP towards four different species of aquatic organisms: marine bacteria (Vibrio fischeri), green algae (Scenedesmus vacuolatus), duckweed (Lemna minor) and crustacean (Daphnia magna), were also carried out. All the investigated compounds were detected at least once in the survey. NOR was found to be the most ubiquitous drug with concentrations of up to 442.8 ng L(-1). Moreover, it was established that L. minor is the most sensitive species to the investigated drugs (EC50NOR = 0.13 mg L(-1), EC50ENR = 0.22 mg L(-1) and EC50CIP = 0.34 mg L(-1)). The calculated risk quotient (RQ) values confirmed that the concentrations of the investigated FQs in the environmental samples were at a level of moderate environmental risk (1<RO ≤ 10), however, for CIP they were found to be closer to a level of high environmental risk (RQCIP = 8.1).

Electrochemical detection of fluoroquinolone antibiotics in milk using a magneto immunosensor

An amperometric magneto-immunosensor (AMIS) for the detection of residues of fluoroquinolone antibiotics in milk samples is described for the first time. The immunosensor presented combines magnetic beads biomodified with an antibody with a broad recognition profile of fluoroquinolones, a haptenized enzyme and a magnetic graphite–epoxy composite (m-GEC) electrode. After the immunochemical reaction with specific enzyme tracer, the antibody biomodified magnetic beads are easily captured by an electrode made of graphite-epoxy composite containing a magnet, which also acts as transducer for the electrochemical detection. In spite of the complexity of milk, the use of magnetic beads allows elimination of potential interferences caused by the matrix components; hence the AMIS could perform quantitative measurements, directly in these samples, without any additional sample cleanup or extraction step. The immunosensor is able to detect up to seven different fluoroquinolones far below the MRLs defined by the UE for milk; for example ciprofloxacin is detected directly in milk with an IC₅₀ of 0.74 μg/L and a LOD of 0.009 μg/L. This strategy offers great promise for rapid, simple, cost-effective, and on-site analysis fluoroquinolones in complex samples.

Development and validation of stability-indicating high performance liquid chromatography method to analyze gatifloxacin in bulk drug and pharmaceutical preparations

Quantitative determination of gatifloxacin in tablets, solid lipid nanoparticles (SLNs) and eye-drops using a very simple and rapid chromatographic technique was validated and developed. Formulations were analyzed using a reverse phase SUPELCO® 516 C-18-DB, 50306-U, HPLC column (250 mm × 4.6 mm, 5 μm) and a mobile phase consisting of disodium hydrogen phosphate buffer:acetonitrile (75:25, v/v) and with orthophosphoric acid pH was adjusted to 3.3 The flow rate was 1.0 mL/min and analyte concentrations were measured using a UV-detector at 293 nm. The analyses were performed at room temperature (25 ± 2 °C). Gatifloxacin was separated in all the formulations within 2.767 min. There were linear calibration curves over a concentration range of 4.0-40 μg.mL(-1) and correlation coefficients of 0.9998 with an average recovery above 99.91%. Detection of analyte from different dosage forms at the same Rt indicates the specificity and stability of the developed method.

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%.

Luminescence screening of enrofloxacin and ciprofloxacin residues in swine liver after dispersive liquid-liquid microextraction cleanup

A luminescence method was developed to screen residues of enrofloxacin (ENRO) and its metabolite, ciprofloxacin (CIPRO), in swine liver. Target analytes were extracted in acetonitrile/1.5% trifluoroacetic acid/NaCl, cleaned up by dispersive liquid-liquid microextraction (DLLME), and finally detected by terbium-sensitized luminescence (TSL) using a time-resolved luminescence photometer. CIPRO yielded slightly lower TSL response than ENRO, so a common threshold was derived from CIPRO and applied to both fluoroquinolones. Among 37 samples randomly spiked with CIPRO or ENRO up to 1 μg/g, all 19 samples spiked above the 500 ng/g tolerance were correctly screened as positive with no false negatives, but 3 of 18 samples spiked below 500 ng/g were classified as positive. This method minimized the use of chlorinated solvents and significantly improved sample throughput.

Preliminary occurrence studies of antibiotic residues in Hong Kong and Pearl River Delta

An improved liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to investigate the occurrence of selected antibiotic residues in Hong Kong and Pearl River Delta. LC and MS parameters were optimized to produce the maximum analytical responses for each compound. The established method targeted five groups of antibiotics, namely, macrolides, sulfonamides, tetracyclines, quinolones, and amphenicols. The method was validated for three types of environmental water matrices, namely, reservoir, river, and estuarine waters. Low detection limits of 0.17-0.18 ng/L for macrolides, 0.22-0.34 ng/L for quinolones, 0.67-1.65 ng/L for tetracyclines, and 0.27-0.56 ng/L for sulfonamides were obtained. No apparent interferences were observed in the chromatograms of all antibiotics groups. The developed method was preliminarily used to analyze water samples collected from Yuen Long River in New Territories, Hong Kong and four sites along the Pearl River Delta. Results showed that high level of tetracycline was found among the groups tested in the local river samples. In Pearl River Delta, we identified significant levels of erythromycin, roxithromycin, and sulfadiazine in Shenzhen Reservoir.

Production of the broad specific monoclonal antibody against sarafloxacin for rapid immunoscreening of 12 fluoroquinolones in meat

The objective of this study was to produce a generic antibody for immunoassay of fluoroquinolone drugs in meat. Two novel haptens of sarafloxacin were synthesized that were used to produce the monoclonal antibodies. The obtained monoclonal antibodies simultaneously recognized 12 fluoroquinolone drugs (sarafloxacin, diflocaxin, marbofloxacin, ofloxacin, ciprofloxacin, enrofloxacin, norfloxacin, pefloxacin, lomefloxacin, amifloxacin, enofloxacin and danofloxacin). After evaluation of different coating antigen/antibody combinations, a heterologous competitive indirect enzyme linked immunosorbent assay (ELISA) was developed to determine the 12 drugs. The crossreactivities to these analytes were in the range of 18%-113% and the limits of detection were in the range of 0.8-6.5 ng/mL depending on the compound. Eight fluoroquinolones licensed as veterinary drugs in China were fortified into blank chicken for ELISA analysis. The recoveries were in the range of 67.6%-94.6% with coefficients of variation lower than 12.4%. Therefore, this method could be used as a screen tool for routine monitoring of the residues of these fluoroquinolone drugs in animal derived foods.

Analysis of quinolone antibiotic derivatives in sewage sludge samples by liquid chromatography-tandem mass spectrometry: comparison of the efficiency of three extraction techniques

This work presents a comparison of three extraction techniques -ultrasound-assisted extraction (USE), microwave-assisted extraction (MAE) and pressurized liquid extraction (PLE) - and evaluates their efficiency in the determination of quinolone antibiotics in sewage sludge samples. Extraction parameters for each technique were optimized using design of experiments, and the compounds were detected and quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS), operating in positive electrospray ionization (ESI) mode. The use of two selected reaction monitoring transitions for each compound allowed simultaneous quantification and identification in one run. Analytes were separated in less than 10 min. Marbofloxacin and cincophen were used as surrogates for amphoteric and acid quinolones, respectively. The limits of detection (LODs) were between 2 and 5 ng g(-1), and the limits of quantification (LOQs) were between 4 and 18 ng g(-1) for the various analytes. The inter- and intra-day variability was <7%. Due to the absence of certified reference materials (CRMs), the method was validated using matrix-matched calibration and a recovery assay with spiked samples. Recovery rates were between 97.9% and 104.8%. Statistical comparison demonstrated no significant differences between the three extraction techniques. The methods were successfully applied for the determination of quinolones in sewage sludge samples collected from different wastewater treatments plants (WWTPs) located in the province of Granada (Spain). The analytical methods developed here may be useful for the development of more in-depth studies on the occurrence and fate of these commonly used pharmaceuticals in WWTPs and in the environment.

Micelle enhanced and terbium sensitized spectrofluorimetric determination of danofloxacin in milk using molecularly imprinted solid phase extraction

An efficient molecularly imprinted solid phase extraction (MISPE)-spectrofluorimetric method was developed to sensitively determine danofloxacin (DAN) in milk samples. Solid phase extraction procedure using MISPE cartridges was first performed on milk samples and then spectrofluorimetric determination was done at 546 nm using an excitation wavelength of 285 nm in presence of terbium and sodium dodecyl benzene sulfonate (SDBS). It was found that SDBS significantly enhanced the fluorescence intensity of the DAN-Tb(3+) complex. Various factors affecting the fluorescence intensity of DAN-Tb(3+)-SDBS system were studied and conditions were optimized. The enhanced fluorescence intensity of the system (ΔF) showed a good linear relationship with the concentration of DAN over the range of 8.4×10(-9)-3.4×10(-7) mol L(-1) with a correlation coefficient of 0.9996. The detection limit was determined as 2.0×10(-9) mol L(-1) and the limit of quantification was determined as 6.5×10(-9) mol L(-1). The MISPE-spectrofluorimetric procedure was successfully applied to the determination of DAN in milk samples. The method is simple, rapid, sensitive and allows interference free determination of DAN in complex fluorescent matrices like milk. The method can be used to determine whether the DAN residues in milk exceed MRLs or not.

Analysis of fluoroquinolones in animal feeds by liquid chromatography with fluorescence detection

An analytical method for the analysis of six fluoroquinolones (FQs) in animal feeds was developed. The sample treatment consists of a simple and rapid extraction of the analytes by manual shaking with an acetonitrile-water mixture containing hydrochloric acid without further sample cleanup. Matrix effects were minimized by diluting the extract with water. Determination was carried out by liquid chromatography using fluorimetric detection. The method was validated in-house in four different feed matrices (poultry, cow, pig, and lamb feed). Mean recoveries ranging from 80 to 105%, with relative standard deviations below 12%, were achieved from spiked animal feed samples on the 0.2-2.0 μg/g level. No relevant differences were observed between the studied feeds, this ensuring that the method was reliable for a wide variety of feed matrices. Decision limit and detection capability values are below 0.08 and 0.13 mg/kg, respectively, for most FQs. The results obtained demonstrate the feasibility of the analytical method developed for a routine use to control the illegal use of these substances in feeding stuffs.