Immunoassay simplified

An additional requirement not noted in Table 1 is compliance with GLP7 These practices establish a paper trail for all procedures involved in the determination of residues. With regard to immunoassays, GLPs require calibration of measurement devices such as adjustable pipettors and dedicated spectrophotometers. Computer software output, as noted above, must be verified prior to use. This process can be simplified by limiting the application of specialized software to the operation of an instrument and carrying out the residue calculations in a broadly available spreadsheet such as Excel. On a positive note, in recent years, the software accompanying most microtiter plate readers has become generally easier to use and usually incorporates internal spreadsheets that are compatible with external systems. 

Currently, the methods based on immunoassays are improved by introducing new analytical solutions (Dequaire et al., 2000 Dequaire et al., 2002 Blais et al., 2003 Hildebrandt et al., 2005 Dill et al., 2006 Nichkova et al., 2007) and miniaturizing analytical elements (Bannon et al., 2008 Wolbers et al., 2006a,b). The underlying objectives are to increase the sensitivity of the assays, to broaden the range of applications, and to simplify the analytical protocols. An attempt to replace radioactive... 

Major labelled immunoassays include RIA, ElA, fluoroimmunoassay, chemiluminescence immunoassay, protein microarrays, and simplified immunoassay. 

The parent compounds and the metabolites have very low aqueous, solubility. They have proven difficult to extract from some matrices the current method for ivermectin involves some 41 concentration and clean-up steps preceding HPLC (8). A Merck method for recovering abamectin residues from strawberries and formation of fluorescent derivatives for HPLC analysis has 18 separate steps (9). A recently published two-step solid-phase recovery procedure for ivermectin from serum indicates that it is possible to combine an abbreviated concentration and cleanup method with a sensitive and specific detection system in this case, liquid chromatography (10). An immunoassay for avermectins that could be interfaced with simplified residue recovery protocols is a promising solution to the intensifying demands on regulatory agencies to monitor these compounds. 

Number of antibodies that can be produced is practically unlimited, hence wide development of immunoassays not only for determination of macromolecules, which induce immunoreactions, but also for small molecule analytes inducing such reaction after binding into suitable conjugates. Besides immunoassays carried out in various formats and immunoaffinity liquid chromatography, since many years very broad studies are carried out on design of integrated immunosensors.127129 In principle their construction should simplify the immunochemical determination by elimination various steps necessary in conventional immunoassays based on the use of labels to monitor the immunochemical reaction. In immunochemical process, the... 

Hokama Y. A rapid, simplified enzyme immunoassay stick test for the detection of ciguatoxin and related polyethers from fish tissues. Toxicon 23 939-946, 1985. 

Hokama et al. developed an enzyme immunoassay (EIA) that replaced the RIA. ° The procedure incorporated horseradish peroxidase coupled to the sheep anticiguatoxin, and was similar in efficacy to the earlier RIA, but less expensive and more practical. However, trying to further simplify the enzymatic procedure, Hokama incorporated a coating on the bamboo sticks used as test tools, so they can adsorb the toxins and then be mixed with reagents.This method was proved successful in separating toxic from nontoxic fish. 

Recently, a highly sensitive immunoassay based on the time resolved fluorimetry was developed for the analysis of MCs in water [169]. In order to improve the sensitivity and to simplify the procedure, this method uses a fluorescent lanthanide (Europium) for labeling the MC and the product of the reaction is detected with a time resolved fluorimeter. This method showed a more consistent response at the lowest concentrations and an equal sensitivity compared to the ELISA methods. 

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