Immunochemical methods test-kits

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. 

Selective antibodies are the basis of all immunochemical methods and therefore the development of these antibodies is fundamental to this technology. In the early days of immunochemistry, only polyclonal antisera had been developed, and they have been used for more than 25 years both in academia and in commercial test-kits. Although the sensitivity and selectivity of polyclonal antisera are excellent, these reagents are a mixture of antibodies, and even with the same immunogen different animals will produce... 

As an analytical approach to residue analysis, immunoassay methods are not well characterized, and no validation protocols have been established. The Association of Official Analytical Chemists, whose primary purpose is validation of analytical methods, established a Task Force on Test Kits and Proprietary Methods (2), which has addressed some of the issues relating to immunoassay methods. The International Union of Pure and Applied Chemistry s Commission on Food Chemistry has established a Working Group on Immunochemical Methods, whose first project is to develop draft guidelines on criteria for evaluation, validation, and quality control for r o-immunoassay methods (10). Similar guidelines for EIAs will also be developed. These documents will assist in development and standardization of requirements for precision for both between-laboratories and within-laboratory andyses, accuracy, and ruggedness, and— for qualitative methods— false positive and false negative rates. 

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. 

This study focused on the applicabili of the commercially availaUe immunochemical test kits to adequately screen for aflatoxin in cottonseed undw non-laboratoiy conditions by comparing their performance to laboratoiy results. On a obal e, TLC and immunochemical methods umuld have highest potential use. TLC was used to conflrm the presence and identity of aflatoxins in the test samples. 

Apart from home-made methods, a number of quick, sensitive, and easy-to-perform immunochemical tests are currently available in a kit format. Table... 

At the present time, there are several commercial kits for the quantification of CDT based on the fractionation of CDT and non-CDT serum variants by anion-exchange chromatography with immunochemical detection [176], The main characteristic of almost all of these micro columns is that they do not separate CDT sialoforms and they are quantified as a whole. Therefore, the CDT forms may contain an undetermined amount of trisialo-Tf, which is under debate as to whether it should be considered a CDT form, and that introduces an error in the determination [185,186], Another drawback of the anion-exchange chromatographic methods is that they fail to detect genetic variants, which may give rise to incorrect determination of CDT or even false-positive results when sera from individuals with genetic Tf variants are analyzed [177,186]. Some authors have claimed that the separation of individual Tf sialoforms is a more accurate procedure than CDT quantification as a whole [68,69,185,186], One of these commercial tests was compared with HPLC and CZE methods to conclude that the data obtained needed to be systematically confirmed by HPLC or CZE [187], In spite of these drawbacks, these kits are still convenient for routine analysis due to their speed. 

---