Commercially available immunoassay test kits

Table I. Commercially Available Immunoassay Test Kits for Aflatoxins...

The time required for complete analysis using any of the above kits was about 30 minutes depending on the amount of time required for the filtration of the sample. In summary, any of the above immunoassay tests could be use for screening of animal feeds down to a level of 20 ppb. Since the above study, the USDA recently completed a comparative study on six commercially available aflatoxin test kits including the above four with... 

A variety of immunoassay test kits for androgens are available from commercial sources. Table 4 indicates some of the most important companies commercializing these assays. 

PCBs in soils and wastewaters can be rapidly screened on site or in the laboratory by immunoassay technique (Chapter 1.13). Immunoassay test kits are now commercially available from many suppliers. The samples can be tested at the calibration levels of 1 to 50 ppm. The kit primarily contains antibody-coated test tubes or magnetic particles, assay diluent, PCB-enzyme conjugate, a color-forming substance, and a solution to quench the reaction. The method does not distinguish accurately one Aroclor from another. PCBs can be measured semiquantitatively by comparing the optical density of the color formed in the sample against a set of calibration standards using a spectrophotometer. 

Several qualitative and quantitative immunochemical methods for CAP analysis in biological matrices of animal origin have been described [101,102, 104,105] (see Table 3). Van de Water et al. [ 102] described an ELISA that detected CAP in swine muscle tissue with an IC50 value of 3 ng mL1. This immunoassay was improved and subsequently optimized incorporating the streptavidin-biotin amplification system. There are also several commercially available test kits (see Table 4). RIDASCREEN is a competitive enzyme immunoassay for the quantitative analysis of CAP residues in milk, eggs, and meat in a microtiter plate. The measurement is made photometrically, obtaining a LOD of 100 ng L 1 in meat and eggs and 150 ng L 1 in milk. The test has been also applied to the analysis of tetracyclines. 

As occurred with the other antibiotics, commercial immunoassay formats, also available as kits for tetracyclines and penicillins such as the Parallux, the LacTek, or the Charm II, have also been placed on the market for the analysis of sulfonamides (see Table 4). Thus, the Parallux detects sulfamethazine and sulfadimethoxine in raw milk with a LOD of 10 pg L1. The Charm II detects almost all sulfonamides in honey and milk with a LOD in the range from 1 to 10 pg L, whereas LacTek is able to detect sulfamethazine. Moreover, the 5101SULlp and 5101SUDAlp tests reach LOD values for sulfamethazine and sulfadiazine of around 0.2 pg L 1 and they have been applied to the analysis of urine, milk, and plasma. These tests have proved to be efficient as a point of care for on-site applications on farms. Moreover, commercially available antibodies can be found from several sources such as Silver Lake Research, US Biological, Cortex Biochem. Inc., Accurate Chemical Scientific, Fitzgerald Industries International Inc., and Biotrend Chemikalien GmbH. 

Polynuclear aromatic hydrocarbons (PAH) are aromatic compounds that contain two or more benzene rings fused together. These substances may be analyzed by HPLC, GC, GC/MS and enzyme immunoassay techniques. The latter is a rapid screening method that may be applied for a qualitative or semiquanti-tative determination Test kits are commercially available for such screening. U.S. EPA (1995) has specified a method (Draft Method 4035) that detects a range of PAHs to different degrees and measures the composite of individual responses to determine the total PAHs in the sample. 

The commercially available Enzygnost HBe monoclonal kit (distributed by Dade Behring) can be considered as an example for an immunoassay which combines many favorable features, e.g. nonisotopic label, sandwich immunoassay principle, use of monoclonal antibodies, determination of antigen and anti-antigen antibodies in a single test, microtiter plate format, possibility for semi- and fully automation. 

Several field sereening test kits are available for the detection of TNT in soil and water. The most common methods can be categorized into immunoassay and colorimetric based methods. Strategic Diagnostics [4] has two immunoassay based methods commercially available in the market ... 

The use of immunoassay techniques for the determination of PAHs has been reviewed. Immunoassay is based on the coupling of a specific biological antibody in the detection device with the analyte either directly in water or extracted from solid samples and diluted in buffer solution. Enzyme-linked immunosorbent assay (ELISA) is the most common immunoassay technique employed in commercially available test kits. Water samples or soil extracts are added with an enzyme conjugate reagent to immobilized antibodies where the conjugate competes with PAHs for binding to the antibodies. ELISA test kit sensitivity and crossreactivity depends on the PAH used to raise the antibody. Antiphenanthrene or antffluoranthene antibodies raised in host animals are the most commonly employed. Test kits will be most sensitive to the PAH from which the antibody was... 

Hurst WJ, Krout ER, Burks WR(2002). A comparison of commercially available peanut ELIS A test kits on the analysis of samples of dark and milk chocolate. J. Immunoassay Immu-nochem., 23(4) 451 59. 

In summary, rapid tests, either immunoassay or enzymatic formats, are the methods of choice when qualitative or semi-quantitative results are required within a short timescale, specifically, around 30 min for targeted residue screening. In general, these assay formats are portable (suitable for in situ testing) and simple to both operate and interpret. A wide variety of test formats are commercially available, many of which are applicable for the detection of classes of antibiotics, such as P-lactams and tetracyclines with detection capabilities at or below the appropriate RLs. As with other test kits, it is important to determine the applicability of the assay for the specific matrix type prior to use as certain matrices are known to contain interference that causes elevated false non-compliant/compliant rates. 

For manual handling several test kits are commercially available. Special fluorometers dedicated for immunoassays have been introduced. For enhancement in sensitivity, microfluorometers with laser excitation have been developed. For special purposes fluorescence microscopes and flow-cytometers are available. Microtiter plates are very frequently used in combination... 

Most routine immunoassay methods for determining FT4 and FT3 concentrations in serum are estimates. These approaches are often more convenient and less expensive than reference methods, and most are available commercially m kit form and on automated immunoassay instruments. Two test strategies are used for estimating the concentrations of free hormones indirect index methods and direct immunoassays. 

Although a number of Immunochemical methods have been used for the analysis of small molecular weight biological substances, only radioimmunoassay (RIA), enyzme-1Inked Immunosorbent assay (ELISA) and Immuno-affinity assay (lAA), have been developed for the analysis of mycotoxins. Recent developments have led to several quick screening tests and more than 10 types of commercial kits have become available In the last few years (8, 10, 13). In most cases, sample after extraction from the solid matrix and diluted In buffer can be directly used In the assay. Since the application of Immunoassay for several mycotoxins are covered by other speakers, I will only briefly highlight some of the recent progress on these methods. 

---