Monoclonal antibody-mediated clean-up procedure for the high-performance liquid chromatographic analysis of chloramphenicol in milk and eggs

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.

Determination of flumequine and doxycycline in milk by a simple thin-layer chromatographic method

Tetracycline and quinolone antibiotics have for many years served as important classes of veterinary drugs. Two representatives of both classes: doxycycline from tetracyclines and flumequine from quinolones are often administered together. When the withdrawal periods are not obeyed, the antibiotic residues may be present in edible products, e.g., in meat, eggs or milk. In the present paper a simple thin-layer chromatography (TLC) screening method is established for determining these drugs in milk. Only two developments of the plate with concentrating zone are needed: one as a clean-up procedure, the other as a proper analysis. The spots were detected both by UV lamp with dual wavelength (254 and 366 nm) and by densitometry.

Bioseparation and bioanalytical techniques in environmental monitoring

The growing use of antibody-based separation methods has paralleled the expansion of immunochemical detection methods in moving beyond the clinical diagnostic field to applications in environmental monitoring. In recent years high-performance immunoaffinity chromatography, which began as a separation technique in biochemical and clinical research, has been adapted for separating and quantifying environmental pollutants. Bioaffinity offers a selective biological basis for separation that can be incorporated into a modular analytical process for more efficient environmental analysis. The use of immunoaffinity chromatography for separation complements the use of immunoassay for detection. A widely used immunochemical detection method for environmental analyses is enzyme immunoassay. The objective of this paper is to review the status of bioaffinity-based analytical procedures for environmental applications and human exposure assessment studies. Environmental methods based on bioaffinity range from mature immunoassays to emerging techniques such as immunosensors and immunoaffinity chromatography procedures for small molecules.

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.

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.

Determination of triasulfuron in soil: affinity chromatography as a soil extract cleanup procedure

Triasulfuron forms one of the group of sulfonylurea herbicides. These are used widely for controlling weeds as they are effective at very low application rates. This effectiveness is responsible for the crop losses due to persistence of trace amounts of the herbicides (< or = 100 pg/g) in the soil. The numerous immunoassays described have been constrained by the fact that the soil extract contains co extractants which interfere in the assays, so much so, that these assays are useless at low levels of herbicide. We describe here the preparation and application of an immunoaffinity column which binds specifically to triasulfuron, thus cleaning up the soil extract. The experiment design is such that this also leads to concentration of the triasulfuron, making it easier to assay reliably using ELISA. Six different soil types were used to validate this procedure. In most cases, the herbicide content could be detected at 100 pg/g (critical phytotoxic herbicide level in soil) with a variation of +/- 20% in the readings.

Analytical strategies for the screening of veterinary drugs and their residues in edible products

The development of analytical strategies for the regulatory control of drug residues in food-producing animals is discussed. Analytical methods for the determination of veterinary drugs in edible products are based on microbiological, immunochemical and physicochemical principles. Because of complexity of biological matrices such as egg, milk and meat, well designed, and often sophisticated, off-line or on-line sample treatment procedures are essential, especially when utilising physicochemical multi-residue screening procedures. Since large series of samples have often to be analysed, automation is increasingly becoming important. Confirmation of the identity of drug residues and validation of the analytical results implies the use of adequate analytical methods. In its turn, this requires well established criteria for those methods and/or equivalent reference methods.

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.

Solid-phase extraction technique for the analysis of biological samples

This article reviews the literature on solid-phase extraction published in the last 10 years. Emphasis has been placed on dealing with samples of biological origin. The sections consist of introduction, history and development, types of columns, selection of a suitable column, types of samples, advantages and applications.

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.

Chromatographic analysis of antibiotic materials in food

The monitoring of food materials for antibiotic residues is an area of increasing concern and importance due to the potential impact on human health. Large-scale screening applications require methods that are rapid, accurate, provide low detection limits and are free from interference. The problem is further complicated by the wide range of chemical functionalities and modes of operation exhibited by the antibiotic materials of physiological significance in use today. As demonstrated, chromatographic methods provide many of the advantages necessary for screening applications. Judicious choice of sample preparation method, separation mode and detection strategy can provide significant immunity from problems associated with the food matrix. Gas chromatography can provide extremely high separation efficiencies, however, only a limited number of antibiotic compounds are inherently volatile enough for direct analysis by gas chromatography. Derivatization to enhance the volatility of the antibiotic is one approach to overcome this limitation. Among the methods available, reversed-phase high-performance liquid chromatography is used extensively for the analysis of many antibiotic systems as it does not require derivatization and it combines relatively high separation efficiencies with low detection limits. The diverse group of properties exhibited by the antibiotic materials in use today suggests that the choice of detection strategy is a key component in the successful development of an analysis technique. Derivatization of the antibiotic material is frequently used to add either a fluorogenic of chromogenic moiety to the antibiotic compound to enhance detection. Derivatization procedures suffer from several limitations which are problematic when making measurements in complicated food matrices. Among the different detection modes utilized for antibiotic analysis, polarimetric detection has the potential to provide extremely selective detection of most antibiotic materials, and this selective response can minimize many of the constraints placed upon the separation system by the sample matrix. Although many of the separation modes used for antibiotic analysis are well developed, separations based on capillary electrophoretic methods have much potential in the field of antibiotic analysis. Future investigations are needed to extend the generality of these techniques and expand their use into the field of food analysis.

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.