Application and validation of a clean-up tandem assay column for screening ochratoxin A in cocoa powder

Regenerable immuno-biochip for screening ochratoxin A in green coffee extract using an automated microarray chip reader with chemiluminescence detection

Ochratoxin A (OTA) can contaminate foodstuffs in the ppb to ppm range and once formed, it is difficult to remove. Because of its toxicity and potential risks to human health, the need exists for rapid, efficient detection methods that comply with legal maximum residual limits. In this work we have synthesized an OTA conjugate functionalized with a water-soluble peptide for covalent immobilization on a glass biochip by means of contact spotting. The chip was used for OTA determination with an indirect competitive immunoassay format with flow-through reagent addition and chemiluminescence detection, carried out with the stand-alone automated Munich Chip Reader 3 (MCR 3) platform. A buffer model and real green coffee extracts were used for this purpose. At the present, covalent conjugate immobilization allowed for at least 20 assay-regeneration cycles of the biochip surface. The total analysis time for a single sample, including measurement and surface regeneration, was 12 min and the LOQ of OTA in green coffee extract was 0.3 μg L(-1) which corresponds to 7 μg kg(-1).

Rapid visual tests: fast and reliable detection of ochratoxin A

This paper reviews the early detection strategies that have been employed for the rapid monitoring of ochratoxin A (OTA) contamination of food. OTA, a mycotoxin mainly produced by some Aspergillus and Penicillium species, is found in cereals, coffee, wine, pork and grapes. To minimize the entry of this mycotoxin into the food chain, rapid diagnostic tools are required. To this end, the potential use of lateral flow devices has also been developed. In this study, we analyze the robustness of test strips using published methods for colorimetric detection. Different test formats are discussed, and challenges in the development of lateral flow devices for on-site determination of OTA, with requirements such as robustness, speed, and cost-effectiveness, are discussed.

An immunochemical test for rapid screening of zearalenone and T-2 toxin

An immunochemically based test for non-instrumental simultaneous detection of zearalenone (ZEA) and T-2 toxin (T2) in feed was developed. The method combines clean-up of sample extract, pre-concentration of analytes by immunoextraction and immunodetection through the enzymatic reaction of horseradish peroxidase (HRP). The test is housed inside a standard 1-mL solid-phase extraction column and consists of three layers: two test layers (one for ZEA and another for T2) with immobilised specific antibodies and one control layer with bound anti-HRP antibodies. Feed extract was passed through an additional column with clean-up layer, which was disconnected after extract application. Total assay time was about 15 min for six samples and detection time was 4 min after chromogenic substrate application. Under optimised conditions a cut-off level for ZEA and T2 of 100 microg/kg was established. Different feed types were analysed for ZEA and T2 contamination by the proposed method and results were confirmed by LC-MS/MS.

Gel-based immunoassay for non-instrumental detection of pyrene in water samples

A new qualitative immunologically based tube test for non-instrumental detection of pyrene (PYR) in water samples was developed. The method combines the pre-concentration of analyte by immunoextraction and its detection by immunoassay using Sepharose 4B-immobilized IgG-fraction of a polyclonal anti-PYR antiserum (immunoaffinity gel) and 1-pyrenebutyric acid-horseradish peroxidase conjugate (PYR-BA-HRP). The immunoaffinity gel was placed in a standard 1-ml SPE column through which a 10-ml aliquot of water sample spiked with 10% acetonitrile was passed. Following, free antibody binding sites were detected by application of PYR-BA-HRP. Four minutes after addition of the chromogenic substrate the results were visually evaluated by occurring or stayed away blue colour development for negative and positive samples, respectively. Total time for assay was about 15 min for six samples. Under optimized conditions a cut-off level for pyrene of 0.04 ng ml(-1) was found. At this defined concentration, a set of spiked samples (n=175) was analyzed and very low rates of false negatives (1.2%) and false positives (4.6%) determined which fulfils the requirement set by Commission Decision 2002/657/EC for a screening method. No interference by other PAH compounds like naphthalene, fluoranthene, phenanthrene, anthracene, and benzo[a]pyrene at a concentration of 20 ng ml(-1), i.e., 500-fold excess compared to the defined cut-off level was observed. Different water types like surface water, tap water, bottled water, and melted snow were analyzed for PYR contamination by the proposed method and results confirmed by HPLC-FLD.

Immunochemical methods for rapid mycotoxin detection: Evolution from single to multiple analyte screening: A review

This review focuses on recent developments in immunochemical methods for detection of mycotoxins, with a particular emphasis on simultaneous multiple analyte determination. This includes high-throughput instrumental analysis for the laboratory environment (microtitre plate enzyme-linked immunoabsorbant assay (ELISA), different kinds of immunosensors, fluorescence polarization immunoassay, and capillary electrophoretic immunoassay), as well as rapid visual tests for on-site testing (lateral-flow, dipstick, flow-through and column tests). For each type of immunoassay, perspectives for multiple analyte application are discussed and examples cited.