Determination of chloramphenicol in swine muscle tissue using a monoclonal antibody-mediated clean-up procedure

Preparation and purification of monoclonal antibodies against chloramphenicol

Monoclonal antibodies (McAbs) against chloramphenicol (CAP) were produced to detect CAP residues, which could be toxic and possesses a potential threat to human health. The CAP-BSA conjugate was obtained by bovine serum albumin (BSA) coupled with CAP, and used to immunize the mice. The splenocytes from the immunized mice were fused with mouse myeloma cells SP2/0 to form hybridoma, which may secrete McAbs against CAP. Hybridomas 1D(1) and 3G(12) secreting McAbs against CAP were obtained by screening. Ascites containing McAbs were prepared by injecting 1 x 10(6) cells of hybridoma 1D(1) and 3G(12) into the abdomen of mice. Protein A affinity chromatography was used to purify McAbs against CAP in a single chromatographic step with recovery yield above 80% and purity above 95% and full recovery of antibody activity. Experiments showed that McAb 3G(12) was highly specific for CAP and had no cross-reactivity with analogues which have a structure similar to CAP. The IC(50) value was 50.8 ng/mL.

Development of a chemiluminescent immunosensor for chloramphenicol

A direct competitive chemiluminescent immunosensor system that exploits the competition between chloramphenicol (CAP) as an analyte and CAP-horseradish peroxidase conjugate as a tracer for binding to an anti-CAP antibody on a solid support was devised by installing a flow-through cell which was connected to an injector and a peristaltic pump inside a dark box, followed by positioning a photomultiplier tube as light detector in front of it. The anti-CAP antibody was immobilized onto positively charged Biodyne B membrane pieces by a dipping procedure. The operating conditions for the immunosensor were selected with respect to substrate composition (0.25, 13.3 and 0.66 mM for luminol, H2O2 and p-iodophenol, respectively), injection volume of the substrate solution (200 microL) and the concentrations of antibody for immobilization (0.10 mg mL(-1)) and tracer (0.030 mg mL(-1)). At these conditions, sensor response according to analyte concentration was well fitted to a linear equation when plotted in semi-logarithmic scale, with the limit of detection for CAP of 10(-8) M. By using the immunosensor, CAP measurement in the model samples prepared from five food materials was conducted.

Sample preparation including sol–gel immunoaffinity chromatography for determination of bisphenol A in canned beverages, fruits and vegetables

The paper describes the development of a very simple method to prepare samples of canned food (beverages, fruits and vegetables) for the determination of bisphenol A by isocratic HPLC with fluorescence detection. The new sample preparation method makes use of the selectivity of bisphenol A antibodies immobilized in a silica matrix by an inexpensive and simple sol-gel technique. In spite of applying highly complex food matrices, immunoaffinity columns could be used for clean-up of at least 15 real samples. Limits of detection (S/N=3) ranged from 0.1 ng/ml for beverages to 4.3 ng/g for vegetables.

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.

Immunoaffinity solid-phase extraction for the trace-analysis of low-molecular-mass analytes in complex sample matrices

Immunoaffinity solid-phase extraction (SPE) sorbents, so-called immunosorbents (ISs), are based upon molecular recognition using antibodies. Thanks to the high affinity and high selectivity of the antigen-antibody interaction, they allow a high degree of molecular selectivity and have shown to be a unique tool in the sample preparation area these last few years. Extraction and clean-up of complex biological and environmental aqueous samples are achieved in the same step and from large volumes when required. Their application to extracts from solid matrixes is solvent-free and more simple than any other clean-up procedure. Single analytes can be targeted, but since an antibody can also bind one or more analytes having structure similar to the one used for its preparation, ISs have been developed for targeting a single analyte and its metabolites. The cross-reactivity was also exploited for developing ISs that could selectively extract a whole class of structurally related compounds. This review describes the current technology used for the synthesis of the ISs, their properties and their field of application. The different parameters governing the antigen-antibody interactions and the solid-phase extraction process are discussed. Emphasis is given to the optimisation of the SPE sequence, especially to the desorption and regeneration steps. The importance of the capacity and its relationship with the analytes recovery and breakthrough volumes is highlighted for class-specific ISs. Multi-class-selective ISs are also presented. Validation studies are reviewed using various certified reference materials. Relevant examples, involving combination with chromatography in both off-line and on-line mode, illustrate the high selectivity provided in various complex matrixes. Miniaturisation is also described, since it allows high throughput of samples.

Solid phase extraction of clenbuterol from plasma using immunoaffinity followed by HPLC

An immuno-extraction column for clenbuterol has been prepared. Optimum conditions for the selective retention and elution of clenbuterol have been developed, based on a modification of our earlier work on morphine, chlortoluron and isoproturon. Clenbuterol could be retained on the immuno-column then eluted in one x one ml fraction using 50% methanol in phosphate buffered saline pH 2. On columns containing antisera (but not to clenbuterol) the clenbuterol was removed in the washing step. HPLC-UV determination gave clean traces. Day-to-day reproducibility was improved by precipitating the plasma proteins with acetonitrile.

Simple high-performance liquid chromatographic column-switching technique for the on-line immunoaffinity extraction and analysis of flunitrazepam and its main metabolites in urine

A sensitive, simple and rapid method without sample pretreatment is presented for the simultaneous determination of flunitrazepam and its main metabolites (norflunitrazepam, 7-amino- and 7-acetamidoflunitrazepam) in urine. The single-step procedure is based on a column-switching technique which uses an immobilized antibody in an extraction column following concentration on a precolumn and separation on an analytical column. UV detection was performed at 254 nm. The reusability of the antibody exceeds 88 runs and a complete analysis was performed in less than 40 min. The method shows coefficients of variation below 9.9% and rates of recovery greater than 92% tested at the level of 50 ng/ml urine. The limit of detection was below 2 ng/ml urine for the four compounds.

Immunoaffinity column cleanup procedure for analysis of ivermectin in swine liver

A simple and sensitive method for the analysis of ivermectin (22,23-dihydroavermectin B1) in swine liver based on immunoaffinity column cleanup is described. The immunosorbent was prepared by coupling polyclonal anti-ivermectin antibodies to carbonyl diimidazole-activated Sepharose CL-4B. After extraction with methanol, ivermectin was cleaned up on an immunoaffinity column, and determined by reversed-phase liquid chromatography with UV absorbance detection at 245 nm. Recoveries of ivermectin from fortified samples of 5-10 micrograms kg-1 levels ranged 85-102%, with coefficients of variation of 6-12%. The limit of detection was 2 micrograms kg-1 in a 5-g samples.

Determination of chloramphenicol in muscle, liver, kidney and urine of pigs by means of immunoaffinity chromatography and gas chromatography with electron-capture detection

A rapid and specific clean-up procedure based on immunoaffinity chromatography (IAC) with polyclonal antibodies for the gas chromatographic determination with electron-capture detection of chloramphenicol in pig muscle tissue, organs and urine is described. A commercially available IAC material was used for the analysis. A decrease in the capacity of the column after being used more than 100 times was observed. Mean recoveries were 69, 54, 62 and 95% for spiked pig muscle tissue, liver, kidney and urine, respectively. The limit of detection was 0.2 micrograms/kg for muscle tissue, 2.0 micrograms/kg for liver and kidney and 0.4 micrograms/kg for urine.

Optimization of the analytical performance of the magnetic sector mass spectrometer for the identification of residual chloramphenicol in shrimp

Chemical noise limits mass spectrometric detection of chloramphenicol (CAP) with electron capture ionization at low resolution, and makes CAP identification at concentrations of 5 parts per billion (ppb) difficult. Increasing the resolution from 1000 to 3500, however, was sufficient to separate the analyte signals from the noise signals, and resulted in a 100 times higher analytical sensitivity. The introduction of sweep gas in the ion source decreased the scattering of the quantitative results on average by a factor of 7, and thereby improved the precision of the analyses to an acceptable level (CV < 10%). Under such conditions, CAP residues of 1.5 and 2.1 ppb in shrimp as determined by electron capture gas chromatography/mass spectrometry can readily be identified by monitoring four diagnostic ions.

Immunoaffinity-chromatography purification of salbutamol in liver and HPLC-fluorometric detection at trace residue level

A method combining immunoaffinity-chromatography (IAC) and high-performance liquid chromatography (HPLC) for the analysis of Salbutamol in liver with a low quantification limit of 1 micrograms/kg has been developed. Salbutamol was extracted with 0.01 mol/L HCl and purified by IAC. The samples were analysed on a liquid chromatograph fitted with a C18 mu-Bondapak column. A fluorometer was used for the detection of salbutamol. Recoveries of 67-80% could be obtained.

Automated high-performance liquid chromatographic determination of chloramphenicol in milk and swine muscle tissue using on-line immunoaffinity sample clean-up

An on-line high-performance liquid immunoaffinity chromatographic (HPLIAC) system for the direct determination of chloramphenicol in milk and swine muscle tissue is described. The system consisted of a dual-column system in which an HPLIAC column was directly coupled to an RP-8 high-performance liquid chromatographic column. Skimmed and deproteinated milk or aqueous muscle tissue extract was directly injected into the HPLIAC column. After a washing step with phosphate-buffered saline, chloramphenicol was desorbed by a glycine-NaCl buffer (pH 2.8) and directly concentrated on the RP-8 column. Next, chromatography was carried out using acetonitrile-sodium acetate buffer as the mobile phase. Chloramphenicol was detected at 280 nm. Mean recoveries from spiked raw milk were 70 +/- 2% (1-50 micrograms/kg) and from spiked swine muscle tissue 64 +/- 2% (10-50 micrograms/kg). The calibration curves were linear in the range 1-200 micrograms/kg spiking levels. Limits of determination were 1 microgram/kg for milk and 10 micrograms/kg for muscle tissue.

Drug residue analysis using immunoaffinity chromatography

The background and applicability of immunoaffinity chromatographic separations and clean-up to drug residue analysis of agricultural commodities is discussed. The uses of antibody specificity for separation and concentration of drug residues are presented. Examples of immunoaffinity chromatography for the determination of residues of (1) nortestosterone and methyl testosterone in swine muscle, urine and bile; (2) chloramphenicol in swine tissue, eggs and milk; (3) clenbuterol in calf urine; (4) zeranol and beta-zearalanolin in calf urine: (5) diethylstilbestrol, dienestrol and hexestrol in calf urine are presented. Further, examples of the successful coupling of immunoaffinity separations with other chromatographic techniques such as gas chromatography and high-performance liquid chromatography are presented.

Chromatographic methods of analysis for penicillins in food-animal tissues and their significance in regulatory programs for residue reduction and avoidance

Chromatographic methods for penicillin analysis in animal tissues play a significant role in the regulation of the use of these drugs in livestock production. Regulatory agencies rely on data generated from these methods to establish withdrawal times and to determine whether presumptive positive tissue samples from slaughtered animals intended for human consumption contain violative levels of penicillins to necessitate regulatory action. The need to develop sensitive, accurate, and reliable methods to support regulatory programs is examined together with emerging techniques that could be taken advantage of to improve the sensitivity and usefulness of current chromatographic methods for tomorrow's regulatory agency.

Liquid chromatographic purification and detection of anabolic compounds

The role of liquid chromatography within methods of analysis for steroids, related compounds and beta-agonists in biological samples is discussed. Special attention is given to the application of liquid chromatography in sample preparation and extract clean-up. Different forms of liquid chromatography, including immunoaffinity chromatography, are compared and evaluated. Methods for confirmation based on gas chromatography-mass spectrometry and cryotrapping Fourier transform infrared spectrometry are discussed.

Analysis of chloramphenicol residues in swine tissues and milk: comparative study using different screening and quantitative methods

Both screening and quantitative methods for chloramphenicol residues in swine tissues and milk were compared, using samples from animals treated with chloramphenicol. For screening purposes a previously developed streptavidin-biotin enzyme-linked immunosorbent assay and a commercially available immunochemical card test were used. For quantitative purposes two previously developed high-performance liquid chromatographic procedures were applied using antibody-mediated clean-up and solid-phase extraction. Some improvements in both methods were also described. The results obtained with the screening tests and those obtained with the quantitative methods correspond well with each other. Using a combination of these methods, an effective control of residues of chloramphenicol can be performed in milk from the 1 microgram/kg level and in swine tissues from the 10 micrograms/kg level.

Immunoaffinity chromatography, its applicability and limitations in multi-residue analysis of anabolizing and doping agents

The use of (multi-)immunoaffinity chromatography in residue analysis is discussed. After an introduction to the immunochemical background an overview of applications is given. A distinction is made between the following methods: (1) single-antibody, single-analyte procedures; (2) single-antibody, multi-analyte procedures; (3) multi-antibody, multi-analyte procedures. It is concluded that immunoaffinity chromatography is superior to most other techniques for sample preparation and extract clean-up. Its advantages in multi-residue procedures are most clear when compared with e.g. high-performance liquid chromatography. In combination with gas chromatography-low-resolution mass spectrometry, very effective multi-residue methods are possible. Most frequently they concern screening procedures which can fulfill the identification criteria for reference methods. It is concluded that the use of (multi-)immunoaffinity chromatography will proliferate further in the 1990s. However, its future viability is highly dependent on the interest of commercial firms and on the involvement of the EC Community Bureau of Reference in manufacturing and supplying the necessary materials.

Analysis of drugs and other toxic substances in biological samples for pharmacokinetic studies

The importance of the role of analysis of drugs and other toxic substances in biological samples (bioanalysis) in medicine, toxicology, pharmacology, forensic science, environmental research and other biomedical disciplines is self-evident. Among these disciplines, bioanalysis plays a special pivotal role in pharmacokinetics. The pharmacokinetic parameters, such as half-life, volume of distribution, clearance and bioavailability, of drugs and other compounds are derived from the concentrations of these analytes assayed in the biological samples collected at specified time points. The capability of analysts to develop sensitive and specific analytical methods for the assay of low concentrations of drugs and other toxic compounds in small amounts of biological samples has contributed significantly to the theoretical advances in pharmacokinetics and its applications in clinical pharmacology and the management of drug therapy in patients. The increased demands for pharmacokinetic applications in turn have stimulated the innovation and improvement in bioanalytical technologies. The reliability of the pharmacokinetic conclusions depends on the accuracy and precision of the analytical methods employed to assay the biological samples. Factors that affect the integrity of the bioanalytical data should therefore be controlled in analysis of biological samples for pharmacokinetics studies. The biological samples for drug concentration determination should be collected as specified in the study protocol with respect to the time and site of sampling. These samples should be processed to avoid extraneous interactions between the analytes and sampling devices or additives resulting in the redistribution of the analytes between components of the biological samples, such as displacement of drug binding and changes in the distribution of the analytes between plasma and red blood cells. The stability of the drugs and other analytes in the samples should also be evaluated to establish the conditions suitable for the transportation and storage of the samples to avoid chemical, photochemical and enzymatic degradation of the analytes. Various technologies have been utilized to assay biological samples for pharmacokinetic studies. The most frequently used are chromatography (high-performance liquid chromatography, gas chromatography and thin-layer chromatography), immunoassays and mass spectrometry.(ABSTRACT TRUNCATED AT 400 WORDS)

Multi-immunoaffinity chromatography: a simple and highly selective clean-up method for multi-anabolic residue analysis of meat

A method for the detection of nortestosterone (NT) in bovine muscle at levels below 1 microgram/kg is described, based on enzymatic digestion of the sample, clean-up by immunoaffinity chromatography after defatting and detection by gas chromatography-mass spectrometry (selected-ion monitoring). The immunoaffinity matrix was prepared after combining the isolated immunoglobulin G fractions from a rabbit antiserum raised against NT and methyltestosterone (MT). Its capacity per millilitre of gel was approximately 10 ng for each of the two steroids. Results for samples containing 0.1 microgram/kg NT and above are described. It is concluded that for multi-residue analysis of samples of muscle at levels as low as 0.1 microgram/kg, multi-immunoaffinity chromatography is a very suitable method of sample clean-up. For purposes of quantification the trideuterated internal standard [16,16,17 alpha-2H3] nortestosterone was synthesized.

Effective monitoring of residues of nortestosterone and its major metabolite in bovine urine and bile

The results of a newly developed method for the detection and identification of residues of nortestosterone (NT) and one of its major metabolites, 17 alpha-nortestosterone (epiNT) are described. The method is based on sample clean-up by immunoaffinity chromatography and detection by high-performance liquid chromatography and/or gas chromatography-mass spectrometry (selected-ion monitoring). All samples of bile from calves that had been treated with NT contained significant amounts of epiNT (6-18 micrograms/l). The NT content of these samples, if detectable, was below 1 microgram/l. Urine contained, with one exception, less than 1 microgram/l epiNT. NT itself if detectable, was, present in urine or bile at levels below 0.1 microgram/l. The results corresponds well with results obtained with a radioimmunoassay procedure.

Immunoaffinity pre-column for selective on-line sample pre-treatment in high-performance liquid chromatography determination of 19-nortestosterone

A liquid chromatographic column-switching system for automated sample pretreatment and determination of the anabolic hormone beta-19-nortestosterone (beta-19-NT) and its metabolite alpha-19-nortestosterone (19-norepitestosterone) in calf urine is described. The system consists of an immunoaffinity pre-column (immuno pre-column) packed with Sepharose-immobilized polyclonal antibodies against beta-19-NT, a second pre-column packed with C18 bonded silica and an analytical C18 column. Urine (25 ml) is directly loaded on the immuno pre-column, where the analytes of interest are trapped by the immobilized antibodies. Next the analytes are desorbed selectively with a solution containing an excess of the cross-reacting steroid hormone norgestrel and transferred, via the second pre-column, to the analytical column. The recovery of beta-19-NT in spiked urine samples was over 95%. The detection limit was 50 ng/l for a 25-ml urine injection. The system showed no loss of analytical performance over a 6-month period, during which about 100 samples were analysed with the same immuno pre-column. The general applicability of this sample pretreatment method is discussed.