Immunosorbents coupled on-line with liquid chromatography for the determination of fluoroquinolones in chicken liver

Fabrication of zwitterionic magnetic microporous organic network for efficient extraction of fluoroquinolone antibiotics from meat samples

A zwitterionic magnetic microporous organic network (MMON-SO3H-NH2) with numerous amino and sulfonic acid ion-pare binding sites was designed and synthesized for efficient magnetic solid-phase extraction (MSPE) of fluoroquinolones (FQs) from meat samples. The core-shell MMON-SO3H-NH2 offered large specific surface area, rapid magnetic responsiveness, good stability, and multiple binding sites for FQs. The density functional theory and independent gradient model evaluations confirmed hydrogen bonding, π-π and ion-pair interactions between MMON-SO3H-NH2 and FQs. Under the optimal conditions, the established MMON-SO3H-NH2-MSPE-HPLC-UV method gave wide linear range (0.15-1000 μg L-1), low limits of detection (0.05-4.5 μg L-1) and limits of quantitation (0.15-13 μg L-1), and high enrichment factors (82.1-99.6) using 3 mg of adsorbent. This work demonstrates that the preparation of zwitterionic MONs is an efficient way to promote the extraction performance of MONs for zwitterionic targets and provides an effective sample pretreatment method for enriching and monitoring FQs in complex food matrices.

Highly-sensitive detection of eight typical fluoroquinolone antibiotics by capillary electrophoresis-mass spectroscopy coupled with immunoaffinity extraction

An off-line procedure, immunoaffinity extraction (IAE), followed by capillary electrophoresis-mass spectroscopy (CE-MS) has been developed for the simultaneous determination of eight typical FQs in environmental water samples.

Development of a broad-specificity monoclonal antibody-based immunoaffinity chromatography cleanup for organophosphorus pesticide determination in environmental samples

An immunoaffinity chromatographic (IAC) method for the selective extraction and concentration of 13 organophosphorus pesticides (OPs, including coumaphos, parathion, phoxim, quinalphos, dichlofenthion, triazophos, azinphos-ethyl, phosalone, isochlorthion, parathion-methyl, cyanophos, disulfoton, and phorate) prior to analysis by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed. The IAC column was prepared by covalently immobilizing a monoclonal antibody with broad specificity for OPs on CNBr-activated Sephrose 4B. The column capacity ranged from 884 to 2641 ng/mL of gel. The optimum elution solvent was 0.01 M phosphate-buffered saline containing 80% methanol. The breakthrough volume of the IAC column was found to be 400 mL. Recoveries of OPs from spiked environmental samples by IAC cleanup and HPLC-MS/MS analysis ranged from 60.2 to 107.1%, with a relative standard deviation below 11.1%. The limit of quantitation for 13 OPs ranged from 0.01 to 0.13 ng/mL (ng/g). The application of IAC cleanup coupled to HPLC-MS/MS in real environmental samples demonstrated the potential of this method for the determination of OP residues in environmental samples at trace levels.

Developing and optimizing an immunoaffinity cleanup technique for determination of quinolones from chicken muscle

An immunoaffinity chromatographic method was developed using an antibody mediated immunosorbent to selectively extract and purify 10 quinolones (marbofloxacin, norfloxacin, ciprofloxacin, lomefloxacin, danofloxacin, enrofloxacin, difloxacin, sarafloxacin, oxolinic acid, and flumequine) in chicken muscle followed by HPLC. The operating conditions of the immunoaffinity chromatography (IAC) column were optimized, and the IAC has been successfully used for the isolation and purification of 10 quinolones from chicken muscle tissue. The optimized immunoaffinity column sample cleanup procedure combined with HPLC coupling to fluorescence detection afforded low limits of detection (0.1 ng g(-1) for danfloxacin and 0.15 ng g(-1) for all other quinolones tested). The method was also applied to determine quinolone residues in commercial muscle samples.

Sample preparation techniques for the determination of trace residues and contaminants in foods

The determination of trace residues and contaminants in complex matrices, such as food, often requires extensive sample extraction and preparation prior to instrumental analysis. Sample preparation is often the bottleneck in analysis and there is a need to minimise the number of steps to reduce both time and sources of error. There is also a move towards more environmentally friendly techniques, which use less solvent and smaller sample sizes. Smaller sample size becomes important when dealing with real life problems, such as consumer complaints and alleged chemical contamination. Optimal sample preparation can reduce analysis time, sources of error, enhance sensitivity and enable unequivocal identification, confirmation and quantification. This review considers all aspects of sample preparation, covering general extraction techniques, such as Soxhlet and pressurised liquid extraction, microextraction techniques such as liquid phase microextraction (LPME) and more selective techniques, such as solid phase extraction (SPE), solid phase microextraction (SPME) and stir bar sorptive extraction (SBSE). The applicability of each technique in food analysis, particularly for the determination of trace organic contaminants in foods is discussed.

Multiresidue determination of fluoroquinolones in milk by column liquid chromatography with fluorescence and ultraviolet absorbance detection

Column liquid chromatography with fluorescence (FLD) and UV-diode array detection (UV-DAD) was used for the simultaneous determination of ciprofloxacin (CIPRO), enrofloxacin (ENRO), marbofloxacin (MARBO), danofloxacin (DANO) and sarafloxacin (SARA) residues in milk, using norfloxacin (NOR) as internal standard. Two solid-phase extraction (SPE) cartridges, were evaluated for sample clean-up and preconcentration, Strata X, based on a modified styrene-divinylbenzene polymer, and Strata Screen A, a mixed anion exchanger/C8 reversed-phase sorbent. The fluoroquinolones (FQs) were separated on a polar endcapped column (AQUA C18). The recoveries for raw milk spiked with the antibiotics at three concentrations close to the maximum residue limit (MRL), were 80-103% for ENRO, CIPRO and DANO, with relative standard deviations (R.S.D.) lower than 6.6%. SARA recoveries were 70% (R.S.D. = 7%) and values in the order of 95% (R.S.D. = 1.5%) were obtained for MARBO at the MRL level. The quantification limits ranged from 2.4 to l0 ng ml(-1) and are below the MRL established for these drugs by the European Union. The method was successfully applied to the analysis of ENRO and its metabolite CIPRO in an incurred milk sample.

Immunoaffinity solid-phase extraction for pharmaceutical and biomedical trace-analysis—coupling with HPLC and CE—perspectives

Immunoaffinity solid-phase extraction (SPE) technique is based upon a molecular recognition mechanism. The high affinity and the high selectivity of the antigen-antibody interactions allow the specific extraction and the concentration of the analytes of interest in one step. In pharmaceutical and biological fields, where most often matrices are complex and analytes at trace-levels, this approach constitutes a unique tool for fast and solvent-free sample preparation. This review presents a general description of this extraction technique and gives numerous examples of its applications in pharmaceutical and biomedical fields. It emphasizes the on-line coupling with chromatographic and electrophoretic separation techniques and introduces new developments. The future directions, especially with regards to the current development of analytical microsystems, are discussed.

Immuno-based sample preparation for trace analysis

Immuno-based sample preparation techniques are based upon molecular recognition. Thanks to the high affinity and high selectivity of the antigen-antibody interaction, they have been shown to be a unique tool in the sampling area. Immuno-based sample preparation methods include the widely encountered immunoaffinity extraction sorbents, so-called immunosorbents, as well as membrane-baed or ultrafiltration techniques. This review describes the new developments and applications that have occurred in recent years with emphasis on (i) the antigen-antibody interactions, (ii) and their importance for the properties and use of immunosorbents, (iii) multiresidue extractions, (iv) the on-line coupling to chromatographic or electrophoretic separations, and (v) the high potential for improving MS detection. The recent use of artificial antibodies for sample pretreatment, so-called molecularly imprinted polymers, is also described.

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.

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

An efficient liquid chromatographic method for the multiresidue analysis of fluoroquinolone antibiotics in chicken tissue has been developed in which quantitation using fluorescence and confirmation with multiple mass spectrometry (MS(n)) was achieved simultaneously. Using this method, eight fluoroquinolones were analyzed in fortified samples of chicken liver and muscle tissue with recoveries at levels of 10-200 ng/g generally in the range of 60-93%, except for desethylene ciprofloxacin, which consistently gave recoveries >or=45%. Relative standard deviations were excellent in all cases, and the limits of detection in ng/g were determined as follows in liver and (muscle): desethylene ciprofloxacin 0.3 (0.1), norfloxacin 1.2 (0.2), ciprofloxacin 2 (1.5), danofloxacin 0.2 (0.1), enrofloxacin 0.3 (0.2), orbifloxacin 1.5 (0.5), sarafloxacin 2 (0.6), difloxacin 0.3 (0.2). Confirmation of the identities of the fluoroquinolones was achieved by monitoring the ratios of two prominent product ions in MS(2) (desethylene ciprofloxacin) or MS(3) (all others). Levels of confirmation as related to ion ratio variability criteria were established. Enrofloxacin and ciprofloxacin were also determined in enrofloxacin incurred chicken liver and muscle using this method.

Determination of ciprofloxacin, enrofloxacin and flumequine in pig plasma samples by capillary isotachophoresis--capillary zone electrophoresis

Quinolones are a group of synthetic antibiotics that are widely used in veterinary medicine. Their residues may remain in tissues, milk, etc. intended for human consumption. The European Union fixes the maximum residue limits (MRLs) of veterinary medicinal products in foodstuffs of animal origin. Analytical methods are therefore needed to determine them in biological samples. In this study, we describe capillary isotachophoresis-capillary zone electrophoresis (ITP-CZE) to analyze three quinolones, enrofloxacin (ENR), ciprofloxacin (CPR) and flumequine (FLU), in pig plasma samples. We used solid-phase extraction with Oasis HLB cartridges as a sample pretreatment clean-up step. Capillary zone electrophoresis (CZE) requires low amounts of sample and is not as sensitive as one would wish. ITP-CZE is an easy way to increase the sample loadability and sensitivity. With this system sensitivity increases 40-fold. The detection limits for CPR, ENR and FLU were 70, 85 and 50 microg l(-1), respectively, which were lower than their MRLs in different kinds of samples. This method is simple and sensitive, and is therefore an alternative tool to the existing HPLC methods for analyzing the residuals of these quinolones in biological samples.

Analysis of quinolone residues in edible animal products

A comprehensive review on the analysis of quinolone antibacterials is presented. The review covers most of the methods described for the determination of quinolone residues in edible animal products. Sample handling, chromatographic conditions and detection methods have been discussed. A summary of the most relevant information about the analytical procedures has been included.

Determination of fluoroquinolones in serum using an on-line clean-up column coupled to high-performance immunoaffinity-reversed-phase liquid chromatography

A simple, rapid and reliable method for the simultaneous analysis of the fluoroquinolones ciprofloxacin, enrofloxacin, sarafloxacin, and difloxacin in bovine serum has been developed. Upon injection of serum samples, an on-line protein G-linked column was employed to automatically remove serum components that otherwise would interfere with analyses. A high-performance immunoaffinity chromatography (HPIAC) column containing covalently bound anti-sarafloxacin antibodies was then used to capture the fluoroquinolones while allowing the remainder of the serum components to elute to waste. After binding to the HPIAC column, the fluoroquinolones were eluted directly onto a reversed-phase (RP) column for final separation of the compounds prior to fluorescence detection at excitation and emission wavelengths of 280 and 444 nm, respectively. Due to use of a clean-up column in tandem with a highly selective HPIAC column, the only off-line sample preparation required was dilution (10-fold) in phosphate buffered saline (PBS) and passage of the samples through a 0.2-microm filter to remove particulate matter prior to injection. No significant interferences from the sample matrix were observed, indicating good selectivity with the HPIAC column. The method yielded high recoveries from fortified bovine serum that were >95% for all four fluoroquinolones with good reproducibility (C.V. values <7.0%). The on-line, automated method described here provides a simple, sensitive and specific assay for multiresidue detection of fluoroquinolones in serum.

Separation and quantification of two fluoroquinolones in serum by on-line high-performance immunoaffinity chromatography

To demonstrate that two structurally similar chemicals can be extracted from a complex matrix and then separated from each other on the basis of their relative affinities for an antibody, an automated column-switching system was used, incorporating on-line, high-performance immunoaffinity chromatography (HPIAC). A high-affinity monoclonal antibody (Mab Sara-95) against the fluoroquinolone sarafloxacin was covalently cross-linked to a protein G column and used to capture fluoroquinolones in fortified serum samples. Interference from matrix components adhering nonspecifically to the column was minimized by the insertion of a protein G cleanup column between the injection port and the Mab Sara-95 derivatized HPIAC column. Upon injection, serum samples containing the fluoroquinolones passed through both columns. The cleanup column detained serum components, that otherwise would bind nonspecifically to the HPIAC column, but allowed the fluoroquinolones to pass through unhindered to the HPIAC column. The fluoroquinolones were then eluted from the HPIAC column according to their relative affinities for the antibody, and individual peaks were monitored using fluorescence detection. By using an on-line cleanup column in tandem with an HPIAC column, the fluoroquinolones could be separated from the serum matrix and then separated from each other on the basis of their affinity for Mab Sara-95 without the use of organic solvents or reversed-phase liquid chromatography (RPLC). This method demonstrates true immunoaffinity separation of structurally related compounds in a complex matrix.

Immuno-affinity solid-phase extraction

The measurement of trace organics such as drugs and pesticides at low concentration in biological and environmental samples is a challenging analytical task. Despite recent advances in instrumentation most analysts regard sample preparation as the rate-limiting step in the overall analytical method. In recent years there has been a lot of interest in immobilising antibodies onto solid supports such as silica to provide highly selective solid-phase extraction. This paper reviews the use of immuno-affinity for solid-phase extraction. It uses as examples extraction of chlortoluron and isoproturon from water and morphine and clenbuterol in urine and plasma respectively. An extensive list of other examples is given. Optimisation procedures are discussed in detail.