Commercially available immunoassay

EIAs are more desirable for the measurement of agrochemicals than enzyme-linked immunosorbent assays (ELISAs) for several reasons. EIAs are easier to run, require minimal liquid transfers, and are completed in brief time frames, approximately 40 min for tube assays to 2.5 h for microtiter plate assays. In contrast, ELISAs are more complex, have many steps involving transfer of reagents, and require 6-8 h to complete. Most commercially available immunoassays utilize the EIA format. 

The following methods serve as typical examples of immunoassay-based analytical methods applied to biomonitoring, environmental, and crop tissue analyses. Each method utilized a commercially available immunoassay kit that was combined with sample extraction and cleanup steps as part of an overall residue method. These methods can serve as models for resolution of similar problems. 

Besides these works, there are a lot of commercially available immunoassays. Their main application is directed toward clinical analysis and food quality. Table 4 shows the most representative kits that can be found nowadays on the market. 

CK-MB can be measured in numerous ways. Immunoassays developed in recent years have improved on the analytical and clinical sensitivity and specificity of the earlier immunoinhibition and immunoprecipitation assays. These assays now (1) measure CK-MB directly and provide mass measurements, (2) are easily automated, and (3) provide rapid results (<30 minutes). Mass assays reliably measure low CK-MB concentrations in both samples with low total enzyme activity (<100 U/L) and with high total enzyme activity (>10,000 U/L). Furthermore, no interferences from other proteins have been documented. The majority of commercially available immunoassays that use monoclonal anti-CK-MB antibodies are the same as those listed in Table 5-2 for cardiac troponin assays. Excellent concordance has been shown between mass concentration and activity assays. A primary reference material is commercially available to assist in harmonization. If used for assay standardization, then this material allows... 

B5. Blumsohn, A., Hannon, R. A., and Eastell, R., Apparent instability of osteocalcin in serum as measured with different commercially available immunoassays. Clin. Chem. 41,318-319 (1995). 

Unfortunately, the dose-survival times for the DSP toxins in the mouse assay fluctuate considerably and fatty acids interfere with the assay, giving false-positive results consequently, a suckling mouse assay that has been developed and used for control of DSP measures fluid accumulation after injection of the shellfish extract. Considerable effort has been applied recently to development of chemical assays to replace these bioassays. As a result a good high performance liquid chromatography (HPLC) procedure has been developed to identify individual PSP toxins (detection limit for saxitoxin = 20 fg per 100 g of meats 0.2 ppm), an excellent HPLC procedure (detection limit for okadaic acid = 400 ngg 0.4 ppm), a commercially available immunoassay (detection limit for okadaic acid=lfg per 100 g of meats 0.01 ppm) for DSP, and a totally satisfactory HPLC procedure for ASP (detection limit for domoic acid = 750 ngg 0.75 ppm). 

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

The discussion that follows describes the adaptation of commercially available immunoassay kits for digoxin and phenytoin which were originally intended for use in such a spectrophotometric assay. 

Commercial Immunoassay Kits. Most commercially available immunoassay kits have been developed for determination of pesticides in water. At a minimum, appropriate residue extraction procedures must be developed before these kits can be applied to pesticide residue analysis of foods. Encouraging results have been obtained in preliminary FDA evaluations of several kits (12). For example, in studies of a kit for detection of triazine herbicides, a typical residue extraction solvent (acetonitrile) was used and then diluted with water to levels tolerated by the immunoassay. Visual comparison of color developed for extract, standard, and reagent blank was made for qualitative analysis. Spectrophotometric readings of the color were made for quantitative analysis. 

Some commercially available immunoassay kits are applied to the analysis in forensic biology. Most of them are for qualitative/semiquantitative analysis. Although they are manufactured for clinical purposes and materials, they are also useful for forensic biological analysis with different purposes and materials. For example, an immunoassay kit for detecting prostate-specific antigen (PSA) in serum as a marker of prostate cancer is also applicable for... 

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