Multiresidue analysis of fluoroquinolone antibiotics in chicken tissue using liquid chromatography-fluorescence-multiple mass spectrometry

Ratiometric rapid distinction of two structurally similar fluoroquinolone antibiotics by a Tb/Eu hydrogel

Norfloxacin and ofloxacin are two frequently prescribed second-generation fluoroquinolone antibiotics with an identical 4-quinolone chromophore and hence, are difficult to distinguish by conventional methods (UV or fluorescence). We have designed a Tb3+/Eu3+/cholate cocktail that enabled us to differentiate these two drugs and rapidly measure their concentrations when present together. Additionally, a Tb3+-cholate gel-based paper sensor was developed to detect and quantify them in a single drug containing system with a limit of detection (LOD) well below 100 nM.

Application of Samarium- and Terbium-Sensitized Luminescence via a Multivariate-Based Approach for the Determination of Orbifloxacin

A lanthanide-based optical sensor has been developed for the sensitive and reliable spectrofluorometric determination of the fluoroquinolone antibiotic orbifloxacin (ORLX). Reaction of ORLX and two lanthanide metal ions, Sm(III) and Tb(III), in aqueous buffered solution produced highly fluorescent complexes. Plackett–Burman design (PBD) was used to explore the impact of four factors, pH, temperature (Temp), contact time (CT), and metal volume (MV), on the fluorescence intensity (FI) of the produced complexes. The obtained data showed that pH was the most significant variable. A blend of pH = 5.0, MV = 2.0 mL, T = 25°C, and CT = 10 min was used to achieve the maximum FI. FT-IR and Raman analyses were performed for the crystals of the as-prepared complexes. Obtained data showed shifting in most of the absorption bands, confirming the complexation of ORLX with both metal ions. Job’s method showed that the stoichiometry for the reaction of ORLX with Sm(III) and Tb(III) was 1 : 1. The proposed method was validated following the ICH guidelines. Injection formulation was analyzed successfully with the developed method with high recovery (99.42–100.91%). The detection and quantification limits were 0.987 and 3.289 ng/mL for the ORLX-Sm(III) complex and 1.020 and 3.399 ng/mL for the ORLX-Tb(III) complex, respectively.

Development and validation of UV spectrophotometric method for orbifloxacin assay and dissolution studies

New, simple and cost effective UV-spectrophotometric method was developed for the estimation of orbifloxacin in pharmaceutical formulation. Orbifloxacin was estimated at 290 nm in 0.5 M hydrochloric acid. Linearity range was found to be 1.0-6.0 μg mL-1. The method was tested and validated for various parameters according to main guidelines. The proposed method was successfully applied for the determination of orbifloxacin in tablets. The results demonstrated that the procedure is accurate, precise and reproducible, while being simple, economical and less time consuming. It can be suitably applied for the estimation of orbifloxacin in routine quality control and dissolution studies.

Development and validation of a microbiological agar assay for determination of orbifloxacin in pharmaceutical preparations

Orbifloxacin is a fluoroquinolone with broad-spectrum antimicrobial activity, and belongs to the third generation of quinolones. Regarding the quality control of medicines, a validated microbiological assay for determination of orbifloxacin in pharmaceutical formulations has not as yet been reported. For this purpose, this paper reports the development and validation of a simple, sensitive, accurate and reproducible agar diffusion method to quantify orbifloxacin in tablet formulations. The assay is based on the inhibitory effect of orbifloxacin upon the strain of Staphylococcus aureus ATCC 25923 used as test microorganism. The results were treated statistically by analysis of variance and were found to be linear (r = 0.9992) in the selected range of 16.0–64.0 μg/mL, precise with relative standard deviation (RSD) of repeatability intraday = 2.88%, intermediate precision RSD = 3.33%, and accurate (100.31%). The results demonstrated the validity of the proposed bioassay, which allows reliable orbifloxacin quantitation in pharmaceutical samples and therefore can be used as a useful alternative methodology for the routine quality control of this medicine.

Multiresidue analysis of antibiotics in food of animal origin using liquid chromatography-mass spectrometry

Antibiotics are the most important drugs administered in veterinary medicine. Their use in food-producing animals may result in antibiotic residues in edible tissues, which are monitored to protect human and animal health, support the enforcement of regulations, provide toxicological assessment data, and resolve international trade issues. This chapter provides basic characterization of the most important classes of antibiotics used in food-producing animals (aminoglycosides, amphenicols, β-lactams, macrolides and lincosamides, nitrofurans, quinolones, sulfonamides, and tetracyclines), along with examples of practical liquid chromatographic-(tandem) mass spectrometric methods for analysis of their residues in food matrices of animal origin. The focus is on multiresidue methods that are favored by regulatory and other food testing laboratories for their ability to analyze residues of multiple compounds in a time- and cost-effective way.

Broad-specific antibodies for a generic immunoassay of quinolone: development of a molecular model for selection of haptens based on molecular field-overlapping

A new molecular model for quinolone haptens was developed based on molecular field-overlapping. The quanlitive modeling of 3-D conformations showed that the conformation difference among quinolones is caused mainly by the different substitutes at the 1 and 7 positions. The 8-substitute also showed some effect by its inter-reaction with the 1-substitute. The conformational similarity of 27 quinolones to each other was for the first time calculated and exploited for a selection of haptens according to desired broad specificity of corresponding antibodies. The developed model was preliminarily validated with antibodies against different quinolones. A significant positive correlation (R = 0.7793) was observed between calculated overlapping coefficients of haptens and the cross-reactivity of corresponding polyclonal antibodies (Pabs), which confirmed the overall accuracy of the developed model and its application in quantitative structure-activity relationship analysis. On the basis of molecular modeling results, the strategy for the production of broad specific antibodies against quinolones was suggested and the potentiality of several candidates was predicted.

Implementation of terbium-sensitized luminescence in sequential-injection analysis for automatic analysis of orbifloxacin

Orbifloxacin (ORBI) is a third-generation fluoroquinolone developed exclusively for use in veterinary medicine, mainly in companion animals. This antimicrobial agent has bactericidal activity against numerous gram-negative and gram-positive bacteria. A few chromatographic methods for its analysis have been described in the scientific literature. Here, coupling of sequential-injection analysis and solid-phase spectroscopy is described in order to develop, for the first time, a terbium-sensitized luminescent optosensor for analysis of ORBI. The cationic resin Sephadex-CM C-25 was used as solid support and measurements were made at 275/545 nm. The system had a linear dynamic range of 10-150 ng mL(-1), with a detection limit of 3.3 ng mL(-1) and an R.S.D. below 3% (n = 10). The analyte was satisfactorily determined in veterinary drugs and dog and horse urine.

Development of an immunochromatography strip for the rapid detection of 12 fluoroquinolones in chicken muscle and liver

A rapid and sensitive colloidal gold immunochromatography test strip based on one monoclonal antibody with broad-specificity, which can detect 12 fluoroquinolones (FQs), was developed. Antigen and goat anti-mouse IgG were respectively drawn on NC membrane as test line and control line. Gold-labeled antibody was added on a pad and put on one end of the membrane. Fluoroquinolones in sample solution compete with antigen combined on NC membrane for the gold-labeled antibody. When enough fluoroquinolone exists, the test line vanishes as there are no spare gold-labeled antibodies that can bind with antigen on the membrane. The control line always exists when the antibody is activated. The lowest detection limits of the FQs in spiked chicken muscle and chicken liver samples were 25 ng mL(-1) for norfloxacin and pefloxacin. The lowest detection limit for the other 10 FQs (enrofloxacin, ciprofloxacin, norfloxacin, flumequine, pefloxacin, ofloxacin, lomefloxacin, enoxacin, danofloxacin, amifloxacin, oxolinic acid, and marbofloxacin) was 50 ng mL(-1). The whole process involving sample preparation and detection can be finished in <10 min. The results demonstrate that the developed method can be potentially used as a screening tool for the determination of 12 FQ residues in a large amount of samples on site.

Development of an HPLC multi-residue method for the determination of ten quinolones in bovine liver and porcine kidney according to the European Union Decision 2002/657/EC

A sensitive multi-residue analytical method was developed for the determination of ten quinolones: enoxacin, ofloxacin, norfloxacin, ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin, oxolinic acid, nalidixic acid, and flumequine in bovine liver and porcine kidney. A simple liquid extraction step followed by a solid phase extraction clean up procedure was applied for the extraction of quinolones from liver and kidney tissues. Recoveries of the extraction varied between 82 and 88% for bovine liver and 92 and 95% for porcine kidney. Separation was performed on an ODS-3 PerfectSil Target (250 x 4 mm) 5 microm analytical column at 25 degrees C. The mobile phase consisted of a mixture of TFA 0.1%-CH(3)CN-CH(3)OH, delivered at a flow rate of 1.2 mL/min according to a gradient program. Elution of quinolones and the internal standard (caffeine, 7.5 ng/microL) was complete within 27 min. Photodiode array detection was used for monitoring the eluants at 275 and 255 nm. The method was fully validated according to the European Union Decision 2002/657/EC, determining linearity, selectivity, decision limit, detection capability, accuracy, and precision. The LODs of the specific method of quinolone determination in bovine liver varied between 3 and 7 microg/kg and in porcine kidney between 3 and 4 microg/kg.

Development and validation of an HPLC confirmatory method for residue analysis of ten quinolones in tissues of various food-producing animals, according to the European Union Decision 2002/657/EC

The aim of this work was to develop an HPLC method for the simultaneous determination of ten quinolones: enoxacin, ofloxacin, norfloxacin, ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin, oxolinic acid, nalidixic acid, and flumequine, in various tissues of food-producing animals. Separation was achieved on a PerfectSil Target column (250 mm x 4 mm, ODS-3, 5 microm), by MZ-Analysentechnik (Germany), at room temperature. The mobile phase consisted of 0.1% TFA-CH(3)OH-CH(3)CN and was delivered by a gradient program of 35 min. The detection and quantitation was performed on a photodiode array detector at 275 and 255 nm. Caffeine (7.5 ng/microL) was used as the internal standard (IS). Analytes were isolated from tissue samples by 0.1% methanolic TFA solution. SPE, using LiChrolut RP-18 cartridges, was applied for further purification. The extraction protocol was optimized and the final recoveries varied between 92.0 and 107.4%. The method was fully validated according to Commission Decision 2002/657/EC. Limits of quantitation for the examined quinolones extracted from each tissue were much lower than the respective Maximum Residue Levels, ranging between 30 and 50 microg/kg for bovine tissue, between 30 and 55 microg/kg for ovine tissue, and between 40 and 50 microg/kg for porcine tissue.

Determination of quinolone residues in shrimp using liquid chromatography with fluorescence detection and residue confirmation by mass spectrometry

The quinolones, oxolinic acid (OXO), flumequine (FLU), and nalidixic acid (NAL), are antibacterial drugs effective against gram-negative bacteria. Quinolones are used in both human and veterinary medicine, but are currently not approved by the U.S. Food and Drug Administration for use in food fish. A liquid chromatography-fluorescence (LC-FL) method was developed to determine OXO, FLU, and NAL residues in shrimp. An additional liquid chromatography-mass spectrometry (LC-MS(n)) method was created to confirm these residues using the same sample extract. Samples were prepared with a simple ethyl acetate extraction followed by solvent exchange into 0.2% formic acid and cleaned-up with hexane. Reverse phase chromatography was used to separate the three compounds in both procedures. For the LC-FL determinative method, fluorescence emission was monitored at 369 nm with excitation at 327 nm. With electrospray ionization, the three most abundant ions from the MS3 product ion spectrum were used to identify OXO, FLU, and NAL in the confirmation procedure. Shrimp samples fortified at levels ranging from 7.5 to 100 ng g(-1) were used to validate both methods.

Simultaneous multiresidue determination of tetracyclines and fluoroquinolones in catfish muscle using high performance liquid chromatography with fluorescence detection

Efficient methods are needed for analysis of veterinary drug residues in food. A number of methods are available for single analytes. Multiresidue methods are now increasingly available. It is still rare, however, to find methods not involving mass spectrometry which allow for analysis of more than one class of drug residue. An efficient multiresidue method for the simultaneous determination of fluoroquinolones (FQs) and tetracyclines (TCs) in catfish muscle has now been developed. This method involves an extraction of the analytes with a mixture of acetonitrile and citrate buffer containing magnesium chloride. After centrifugation and evaporation of the supernatants, the residues are determined using high performance liquid chromatography with fluorescence detection. With this method, five fluoroquinolones and three tetracyclines were determined in fortified catfish muscle at levels of 20, 50, and 100 ng g(-1). Average recoveries for ciprofloxacin (CIP), sarafloxacin (SAR), danofloxacin (DANO), enrofloxacin (ENRO), difloxacin (DIF), oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) were in the range of 60-92% with good relative standard deviations. The limits of quantitation ranged from 0.15 to 1.5 ng g(-1). Utilization of the method to successfully analyze catfish muscle samples incurred with enrofloxacin and with oxytetracycline is described.

Dual biosensor immunoassay-directed identification of fluoroquinolones in chicken muscle by liquid chromatography electrospray time-of-flight mass spectrometry

Fluoroquinolones (FQs) are synthetic antibiotics of broad-spectrum antibacterial activity widely used to treat infections in farmed fish, turkeys, pigs, calves and poultry. Monitoring these substances residues is therefore regulated by law. For the detection of FQs, we studied the feasibility of coupling the simultaneous screening of several FQs, using a dual surface plasmon resonance (SPR) biosensor immunoassay (BIA), in parallel, with an analytical chemical methodology for their identification. Six FQs were simultaneously screened at or below their maximum residue level (MRL) in chicken muscle using a multi-FQ BIA for norfloxacin, ciprofloxacin, enrofloxacin, difloxacin and sarafloxacin, and a specific BIA for flumequine. The two BIAs were serially coupled in a multi-channel SPR biosensor featuring a dual BIA in a competitive inhibition format. The samples non-compliant during the screening with the dual BIA were further concentrated and fractionated with gradient liquid chromatography (LC). The effluent was splitted toward two 96-well fraction collectors resulting in two identical 96-well plates. One was re-screened with the dual BIA to identify the immunoactive fractions and direct the identification efforts toward the relevant fractions in the second well-plate with high resolution LC-electrospray time-of-flight mass spectrometry (ESI-TOFMS). The system not only allows the possibility to screen and identify known FQs, but also to discover unknown chemicals of similar structure which show activity in the dual BIA.

New extraction procedure to improve the determination of quinolones in poultry muscle by liquid chromatography with ultraviolet and mass spectrometric detection

The present article aims to develop a new extraction procedure to improve the determination of quinolones in chicken muscle. This new determination method was validated using liquid chromatography-ultraviolet detection (LC-UV) and liquid chromatography-mass spectrometry detection (LC-MS), which has special bearing on stability studies. The results obtained by using the method were compared with the results obtained with a previous methodology. The new extraction procedure presents a sensitivity low enough to determine concentration of these drugs below the permissible maximum residue limits (MRL) in chicken muscle and is less time consuming than the previous methodology.

Analysis of veterinary drug residues in shrimp: A multi-class method by liquid chromatography–quadrupole ion trap mass spectrometry

A liquid chromatography-mass spectrometry (LC-MS) method was developed to screen and confirm veterinary drug residues in raw shrimp meat. This method simultaneously monitors 18 drugs of different classes, including oxytetracycline (OTC), sulfonamides, quinolones, cationic dyes, and toltrazuril sulfone (TOLS). The homogenized shrimp meat is extracted with 5% trichloroacetic acid. The extract is further cleaned using polymer-based SPE. A 50 mm phenyl column separates the analytes, prior to analysis with an ion trap mass spectrometer interfaced with an atmospheric pressure chemical ionization source. This method is able to confirm oxytetracycline residues at 200 ng/g, toltrazuril sulfone at 50 ng/g, sulfaquinoxaline at 20 ng/g, and the other 15 drugs at 10 ng/g or lower levels. An estimate of the level of residues can also be made so that only confirmed samples above action levels will be sent for quantitation. The method is validated with both fortified and incurred samples, using multiple shrimp species as well. This multi-class method can provide a means to simultaneously monitor for a wide range of illegal drug residues in shrimp.

Determination of fluoroquinolones in chicken tissues by LC-coupled electrospray ionisation and atmospheric pressure chemical ionisation

The aim of this work was to develop a method for determining seven quinolones (ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, oxolinic acid and flumequine) in chicken muscle by LC coupled to MS. Two ionisation techniques, ESI and atmospheric pressure chemical ionisation (APCI) were compared using standard solutions. LOD and LOQwere determined under the optimised conditions for the two sources. The ESI was found the best for the purpose. The optimised method (LC-ESI-MS) was validated for the simultaneous analysis of the quinolones regulated by European Community in spiked chicken tissues, using norfloxacin as internal standard. Recoveries obtained varied in the range 60-109%. This method was compared with LC-UV method established previously.

The simultaneous separation and determination of five quinolone antibotics using isocratic reversed-phase HPLC: Application to stability studies on an ofloxacin tablet formulation

A rapid and reliable HPLC method was developed for the simultaneously separation and quantitation of five quinolones antibiotics; nalidixic acid, norfloxacin, ofloxacin, ciprofloxacin and lomefloxacin. All five tablet formulations of individual quinolone antibiotics were routinely assayed without interference. The calibration curves were linear (r2> or =0.999) over the concentration range of 1.20-4.8 mg/100 ml. Selectivity, precision, sensitivity and accuracy were established and the method is stability indicating with respect to ofloxacin. The limit of detection and quantitation for ofloxacin was 18 and 36 microg/100 ml, respectively. The separation was performed on a Phenomenex ODS C18 column using an isocratic, ion-pairing mobile phase consisting of 35% (v/v) aqueous acetonitrile together with tetrabutylammonium acetate, sodium dodecyl sulphate and citric acid (pH* 3.4). All analyses were conducted at ambient temperature and was monitored using a Diode Array UV/VIS detector set at wavelengths 235, 254, 275 and 300 nm.

Determination of fluoroquinolones in edible animal tissue samples by high performance liquid chromatography after solid phase extraction

In the present work, a rapid, accurate, and sensitive method has been developed for the quantitative determination of five fluoroquinolones (enoxacin, ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin) in edible animal tissues (muscle tissue, liver, kidney, and eggs). The separation was accomplished on an Inertsil (250 x 4 mm) C8, 5 microm, analytical column, at ambient temperature within 15 min. The mobile phase consisted of a mixture of citric acid (0.4 mol L(-1))-CH3OH-CH3CN (87:9:4% v/v). UV detection at 275 nm yielded the following limits of detection: 100 pg per 20 microL injected volume for enoxacin, norfloxacin, and ciprofloxacin, 20 pg for ofloxacin, and 200 pg for enrofloxacin. Peaks in real samples were identified by means of a photodiode array detector. The method was validated in terms of intra-day (n = 8) and inter-day (n = 8) precision and accuracy. Tissue samples were purified from endogenous interference by solid-phase extraction using Oasis HLB cartridges. The solid-phase extraction protocol was optimized in terms of retention and elution. Recovery rates at fortification levels of 40, 60, and 80 ng/g ranged from 82.5% to 111.1%. The applicability of the method was examined using real samples from a chicken treated orally with the five studied fluoroquinolones.

Rapid fluorescence screening assay for enrofloxacin and tetracyclines in chicken muscle

A simple, rapid fluorescence assay was developed for screening both enrofloxacin (ENRO) and tetracyclines in chicken muscle at the U.S. tolerance levels (300 ng/g and 2 microg/g, respectively). Screening for both classes of antibiotics is accomplished using one extraction, thus simplifying and expediting the process. The method requires an initial extraction of chicken muscle with 1% acetic acid in acetonitrile, centrifugation, and analysis of the supernatant for ENRO fluorescence. After addition of ammonium hydroxide, magnesium chloride, and methanol, followed by centrifugation and filtration, the supernatant can be measured for tetracycline fluorescence. Chlortetracycline (CTC) was chosen as a representative tetracycline to demonstrate the method, as it displays intermediate sensitivity among the three tetracyclines approved in the U.S. Comparison of the fluorescence of control and tolerance-level-fortified samples of both ENRO and CTC shows no overlap. Setting a threshold as the average fortified fluorescence minus 3sigma allows for successful screening, as illustrated with blind samples as controls or fortified with ENRO and/or CTC over a range of concentrations. This method can provide an alternative or supplemental approach to currently used microbial screening assays.

Comparison of a bioassay and a liquid chromatography-fluorescence-mass spectrometry(n) method for the detection of incurred enrofloxacin residues in chicken tissues

Regulatory monitoring for most antibiotic residues in edible poultry tissues is often accomplished with accurate, although expensive and technically demanding, chemical analytical techniques. The purpose of this study is to determine if a simple, inexpensive bioassay could detect fluoroquinolone (FQ) residues in chicken muscle above the FDA established tolerance (300 ppb) comparable to a liquid chromatography-fluorescencemass spectrometry(n) method. To produce incurred enrofloxacin (ENRO) tissues (where ENRO is incorporated into complex tissue matrices) for the method comparison, 40-d-old broilers (mixed sex) were orally dosed through drinking water for 3 d at the FDA-approved dose of ENRO (50 ppm). At the end of each day of the 3-d dosing period and for 3 d postdosing, birds were sacrificed and breast and thigh muscle collected and analyzed. Both methods were able to detect ENRO at and below the tolerance level in the muscle, with limits of detection of 26 ppb (bioassay), 0.1 ppb for ENRO, and 0.5 ppb for the ENRO metabolite, ciprofloxacin (liquid chromatography-fluorescence-mass spectrometry(n)). All samples that had violative levels of antibiotic were detected by the bioassay. These results support the use of this bioassay as a screening method for examining large numbers of samples for regulatory monitoring. Positive samples should then be examined by a more extensive method, such as liquid chromatography-fluorescence-mass spectrometry(n), to provide confirmation of the analyte.

Determination of the fluoroquinolone enrofloxacin in edible chicken muscle by supercritical fluid extraction and liquid chromatography with fluorescence detection

A supercritical fluid extraction (SFE) method for the extraction of enrofloxacin from a chicken breast muscle was examined. A liquid chromatograph, equipped with a fluorescence detector, was used for the detection of enrofloxacin. Optimal extraction parameters, such as extraction time, supercritical fluid volume, modifier concentration, pressure, and temperature, were determined by examining SFE recoveries from control muscle samples spiked with enrofloxacin at different levels. In all of the experiments, high recovery values were observed, ranging from 101 to 104%. The extraction of enrofloxacin from real muscle samples was examined in chickens that were treated orally with enrofloxacin. Extraction was carried out by the SFE method after each oral treatment and under optimal extraction conditions at set intervals over time. The SFE, combined with liquid chromatographic analysis, showed that the concentration of enrofloxacin in the chicken muscles decreased continuously with time, giving a negligible concentration 72 h after the treatment. These results suggest that SFE is a useful approach for the extraction of enrofloxacin from chicken breast muscles.

A rapid spectrofluorometric screening method for enrofloxacin in chicken muscle

A simple spectrofluorometric method was developed for screening enrofloxacin (ENRO) in chicken muscle. A single-step extraction with acidic acetonitrile gave the best results without further cleanup. Following centrifugation the supernatants were excited at 324 nm and the emission was measured at 442 nm. Using this procedure, 18 chicken breast samples from 3 producers were tested. The results showed background signal levels significantly lower than those corresponding to 300 microg/kg ENRO, the FDA approved tolerance level. Statistical treatment of these data established a threshold which can be used in subsequent screening of ENRO at the tolerance level. The calibration curve revealed a satisfactory linear relationship (R(2) = 0.9991) in a range of 0-700 microg/kg ENRO in fortified chicken breast. ENRO-incurred samples were examined using this approach, and the results agreed with those obtained from more extensive separation followed by high-performance liquid chromatography. Because the threshold can be set at the 3 sigma limit, reliable screening can be accomplished with an error rate of less than 0.26%. Based on this investigation, a high-throughput screening method for ENRO in chicken tissue is proposed.