Feasibility of high-performance immunochromatography as an isolation method for PCBs and other dioxin-like compounds

Replacing antibodies with aptamers in lateral flow immunoassay

Aptamers have been identified against various targets as a type of chemical or nucleic acid ligand by systematic evolution of ligands by exponential enrichment (SELEX) with high sensitivity and specificity. Aptamers show remarkable advantages over antibodies due to the nucleic acid nature and target-induced structure-switching properties and are widely used to design various fluorescent, electrochemical, or colorimetric biosensors. However, the practical applications of aptamer-based sensing and diagnostics are still lagging behind those of antibody-based tests. Lateral flow immunoassay (LFIA) represents a well established and appropriate technology among rapid assays because of its low cost and user-friendliness. The antibody-based platform is utilized to detect numerous targets, but it is always hampered by the antibody preparation time, antibody stability, and effect of modification on the antibody. Seeking alternatives to antibodies is an area of active research and is of tremendous importance. Aptamers are receiving increasing attention in lateral flow applications because of a number of important potential performance advantages. We speculate that aptamer-based LFIA may be one of the first platforms for commercial use of aptamer-based diagnosis. This review first gives an introduction to aptamer including the selection process SELEX with its focus on aptamer advantages over antibodies, and then depicts LFIA with its focus on aptamer opportunities in LFIA over antibodies. Furthermore, we summarize the recent advances in the development of aptamer-based lateral flow biosensing assays with the aim to provide a general guide for the design of aptamer-based lateral flow biosensing assays.

Development and application of immunoaffinity chromatography for coplanar PCBs in soil and sediment

An immunoaffinity chromatography (IAC) column was developed as a simple cleanup procedure for preparing environmental samples for analysis of polychlorinated biphenyls (PCBs). Soil and sediment samples were prepared using pressurized liquid extraction (PLE), followed by the IAC cleanup, with detection by an enzyme-linked immunosorbent assay (ELISA). Quantitative recoveries (84-130%) of PCB-126 were obtained in fortified sediment and soil samples using the PLE/IAC/ELISA method. These results demonstrated that the IAC procedure effectively removed interferences from the soil and sediment matrices. The IAC column could be reused more than 20 times with no change in performance with 99.9% methanol/0.1% Triton X-100 as the elution solvent. Results of 17 soil and sediment samples prepared by PLE/IAC/ELISA correlated well with those obtained from a conventional multi-step cleanup with gas chromatography/mass spectrometry detection.

Miniaturization in sample treatment for environmental analysis

The increasing demand for faster, more cost-effective and environmentally friendly analytical methods is a major incentive to improve the classical procedures used for sample treatment in environmental analysis. In most classical procedures, the use of rapid and powerful instrumental techniques for the final separation and detection of the analytes contrasts with the time-consuming and usually manual methods used for sample preparation, which slows down the total analytical process. The efforts made in this field in the past ten years have led to the adaptation of existing methods and the development of new techniques to save time and chemicals, and improve overall performance. One route has been to develop at-line or on-line and, frequently, automated systems. In these approaches, miniaturization has been a key factor in designing integrated analytical systems to provide higher sample throughput and/or unattended operation. Selected examples of novel developments in the field of miniaturized sample preparation for environmental analysis are used to evaluate the merits of the various techniques on the basis of published data on real-life analyses of trace-level organic pollutants. Perspectives and trends are briefly discussed.

Differences in retention of dioxin-like compounds and organochlorinated insecticides on an immunochromatographic column. Interpretation and applicability

The retention of organochlorinated compounds on an immunochromatographic column is studied. The compounds considered are usually found together in real samples of environmental concern, and include chlorinated biphenyls, chlorinated dibenzo-p-dioxins, chlorinated dibenzofurans, and organochlorinated insecticides. The different retention observed for different compounds is interpreted in light of the structural similarities of the compound studied with that used as a hapten to raise the antibodies employed as ligands in the immunochromatographic column. Differences in retention of the organochlorinated compounds on the immunocolumn make it possible to fractionate them. Mixtures of phosphate buffer solution and ACN in different ratios were used as desorption agents. Depending on the percentage of ACN employed, different fractionations of the organochlorinated compounds are obtained. The use of 20% ACN allows fractionation of most insecticides from chlorinated biphenyls, dioxins, and furans. Besides, chlorinated biphenyls of different chlorination degree can be separated. Moreover, pentachlorinated dioxins and pentachlorinated furans are separated from hexachlorinated biphenyls. Fractionation is of critical importance from a practical point of view, as it avoids some of the interferences that otherwise take place during the subsequent gas chromatography/mass spectrometry (GC/MS) analysis of these compounds. In this way, immunochromatography makes it possible to perform in a single step all the processes (extraction, clean-up, concentration, and fractionation) that are needed prior to the GC/MS analysis of these analytes in aqueous samples. An additional advantage of this method is the reusability of the immunoaffinity chromatography column for more than 500 times.

Congener-specific determination of dioxins and related compounds by gas chromatography coupled to LRMS, HRMS, MS/MS and TOFMS

Their characteristics as persistent organic pollutant and their toxicity (2,3,7,8-TCDD is named as a known human carcinogen) make the dioxins and related compounds a focus of interest in environmental analytical chemistry. In view of the widespread distribution of dioxins in the environment, these compounds must be monitored in several matrices, such as air, effluents, soil, sludge and biological samples. The analytical methodologies are especially difficult owing to the complexity of the mixtures of congeners (210 PCDD/Fs and 209 PCBs) and to the low detection limits required (ppb to ppq). Moreover, time-consuming sample preparation steps are needed owing to the presence of a large number of interfering compounds. The different toxicity of each congener requires the development of congener specific methods. This review of trace dioxin determination by mass spectrometry (MS) includes sample preparation and chromatographic separation. In this Special Feature, the use of different MS techniques such as low-resolution MS (LRMS) and high-resolution MS (HRMS) is discussed in terms of selectivity and sensitivity. The performances of other MS techniques, such as tandem MS (MS/MS) and time-of-flight MS (ToFMS), are compared. Quantification techniques, especially the isotopic dilution method, are also discussed. Conclusions and future perspectives are outlined.

Recent advances in the mass spectrometric analysis related to endocrine disrupting compounds in aquatic environmental samples

An overview of mass spectrometric methods used for the determination of endocrine disrupting compounds (EDCs) in environmental samples is presented. Among the EDCs we have selected five groups of compounds that are of priority within European Union and US research activities: alkylphenols, polychlorinated compounds (dioxins, furans and biphenyls), polybrominated diphenyl ethers, phthalates and steroid sex hormones. Various aspects of current LC-MS and GC-MS methodology, including sample preparation, are discussed.

Dioxins in food: a modern agricultural perspective

This review attempts to cover and summarize the literature available on polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in the environment with regard to problems of interest to agriculture. The coverage of the literature is extensive (120 references) but, by all means, not complete. Issues that are addressed in this review include a background summary of dioxins in the environment and their potential human health risks; current knowledge on the levels of dioxins in the U.S. food supply and comparisons to European data; descriptions of recent food contamination episodes; an evaluation of methods that may reduce incurred levels of dioxins in livestock and meats; and the status and limitations of dioxin analysis and rapid screening methods with regard to widespread monitoring programs. Research areas in agriculture where data and experimental results are scarce or nonexistent are also pointed out.