Isotopic dilution radioimmunoassay

Radioactivity (17) Isotope dilution-radioimmunoassay (19) Ultraviolet (17) Thin-layer chromatography (16) Gas-liquid chromatography (16) Mass spectrometry (16) HPLC (20)... 

LE Hare, CA Ditzler, M Hichens, A Rosegay, DE Duggan. Analysis of sundilac and metabolites by combined isotope dilution-radioimmunoassay. J Pharm Sci 66 414, 1977. 

The first immunoassay technique was the isotopic dilution radioimmunoassay, developed by Rosalyn Yalow and Solomon Berson for the detection of insulin in human blood. This work gained Yalow a share of the 1977 Nobel Prize for Physiology and Medicine, but Berson was not honored because of Nobel rules stating that the prize cannot be awarded posthumously. The following passage, translated from the presentation speech, explains the technique in simple terms ...As a result of mixing in a test tube a known quantity of radioactive insulin with a known quantity of antibodies against insulin, a... 

The isotopic dilution radioimmunoassay is based on the principle of saturation analysis, which is outlined in Figure 1. A test compound (in this case insulin, represented by X) is quantified by its ability to progressively saturate a suitable reagent (in this case an antibody specific for insulin, represented by Y). In the first step, a known quantity of radioactively labeled tracer insulin (X ) is added to the sample. 

Study of chemical pathways in method development. Isotope dilution methods. Radioimmunoassay very important in biochemistry and medicine. Neutron activation analysis used for trace elements in geo-chemistry, semiconductor technology, pollution studies and forensic science. Relative precision of counting 1% if 104 counts are recorded. Assessment of pollution by radionuclides. 

A most important technique which has been developed as an extension of the isotope dilution principle is that of radioimmunoassay (RIA). Analyses by this method employ substoichiometric amounts of specific binding immuno-chemical reagents for the determination of a wide range of materials (immunogens) which can be made to produce immunological responses in animals such as sheep or rabbits. It is possible to combine the specificity of an immunochemical reaction with the extreme sensitivity of radiotracer detection. Analytical methods based upon these principles have achieved wide applicability in the determination of organic compounds at trace levels. 

Part—VI has been solely devoted to Miscellaneous Assay Methods wherein radioimmunoassay (RIA) (Chapter 32) has been discussed extensively. Various arms of theoretical aspects viz., hapten determinants and purity importance of antigenic determinants and analysis of competitive antibody binding of isotopically labeled compounds. The applications of RIA in pharmaceutical analysis, such as morphine, hydromorphone and hydrocordone in human plasma clonazepam, flurazepam in human plasma chlordiazepoxide in plasma barbiturates, flunisolide in human plasma have been described elaborately. Lastly, the novel applications of RIA-techniques, combined RIA-technique-isotope dilution and stereospecificity have also been included to highlight the importance of RIA in the analytical armamentarium. 

Johnson, L. P., McLeod, J. K., Summons, R. E., and Hunt, N. (1980). Design of a stable isotope dilution gas chromatography/mass spectrometric assay for cAMP Comparison with standard protein-binding and radioimmunoassay methods, Anal. Biochem. 106,285-290. 

A most important technique which has been developed as an extension of the isotope dilution principle is that of radioimmunoassay (R1A). Analyses by this method employ substoichiometric amounts of specific binding immuno ... 

Isotope dilution in combination with the substoichiometric principle is applied in various ways. The most important examples are radioimmunoassay for protein analysis and DNA analysis. In radioimmunoassay, radionuclides are used as tracers and immunochemical reactions for isolation. Radioimmunoassay was first described in 1959 by Yalow and Berson, and since then has found very broad application in clinical medicine, in particular for the measurement of serum proteins, hormones, enzymes, viruses, bacterial antigens, drugs and other substances in blood, other body fluids and tissues. Only one drop of blood is needed, and the analysis can be per-fonned automatically. Today more than 10 immunoassays are made annually in the United States. The most important advantages of the method are the high sensitivity and the high specificity. In favourable cases quantities down to 10 g can... 

Assays radioisotopes are used in several quantitative detection methods of value to chemists. Radioimmunoassay is a quantitative method for measurement of a substance (the analyte) using antibodies which bind specifically to that analyte. Isotope dilution analysis works on the... 

Radioimmunoassay (RIA) is a technique based on the formation of antigen-antibody complex. This technique essentially involves the application of isotope dilution analysis. An antigen is typically a protein of molecular weight greater than 10,000 that stimulates the production of antibody in an animal body. The antigen subsequently binds with the antibody. 

There are no convenient or reliable functional tests of pantothenic acid status, thus assessment is made by direct measurement of whole blood or urine pantothenic acid concentrations. Urine measurements are perhaps the easiest to conduct and interpret, and concentrations are closely related to dietary intake, Whole blood measurements are preferred to plasma, which contains only free pantothenic acid and is insensitive to changes in pantothenic acid intake. Concentrations of pantothenic acid in aU of the above fluids can be measured by microbiological assay, most commonly using Lactobacillus plantarum. Whole blood must first be treated with an enzyme preparation to release pantothenic acid fi om CoA. Other techniques that have been used to measure pantothenic acid in human samples include radioimmunoassay and gas chromatography, Other techniques that have been developed include gas chromatography-mass spectrometry and a stable isotope dilution assay. CoA and AGP can be measured by enzymatic methods. ... 

There are a number of different ways in which isotopes can be used in biological investigations. They can be classified under three main headings analytical techniques, tracer studies, and kinetic-isotope studies. Two important analytical techniques are isotope dilution and radioimmunoassay, both of which depend upon the fact that small amounts of isotopes are very conveniently determined by measurements of their radioactivity. In a tracer study one labels a compound by making ah isotope... 

In the isotope-dilution technique it is necessary to isolate, purify, and assay a sample of the substance under study, and this sometimes presents a difficulty. On the other hand, in the radioimmunoassay (RIA) technique it is not necessary to assay the substance, but only to measure the radioactivity. 

The first quantitation method based on this trapping procedure was developed for TXA 2 formed from exogenous precursor and was a double isotope dilution method [19]. Later a radioimmunoassay was developed for the major epimer of mono-0-methyl TXB2 [222]. This method allowed the assay of TXA2 formed from endogenous precursor [e.g. 223]. 

Radioimmunoassay (RIA) This is widely used to measure hundreds of substances of biological interest. The principle of classical RIA is to obtain the unknown concentration of the unlabeled antigen by comparing its inhibitory effect on the binding of radiolabeled antigen to a specific antibody with the inhibitory effect of known standards. The principle of RIA closely resembles the isotope dilution method. 

See also Archaeometry and Antique Analysis Dating of Artifacts. Bioassays Ovenriew. Drug Metabolism Metabolite Isolation and Identification Isotope Studies. Fertilizers. Food and Nutritional Analysis Meat and Meat Products. Immunoassays, Techniques Radioimmunoassays. Isotope Dilution Analysis. Pesticides. Pharmaceutical Analysis Drug Purity Determination. Process Analysis Overview. Radiochemical Methods Pharmaceutical Applications. Water Analysis Industrial Effluents. 

See also Immunoassays, Techniques Radioimmunoassays. Isotope Dilution Analysis. Radiochemical Methods Radiotracers. Titrimetry Overview. Water Analysis Overview. 

A radioimmunological method, developed by Salmon (1), has been selected for routine purposes and has recently been applied to measurements in total blood samples of endotoxin treated animals (2). Being aware of the discrepancies, often reported between radioimmunoassays (RIA) and chemical measurements (3), a reference method using isotope dilution (ID) and mass spectrometry (MS), i.e. selected ion monitoring (SIM) has been worked out in order to support RiA data. The technique of ID-MS may serve as a reference method as it can provide a specific and accurate means for determination in biological fluids. Ihe accuracy of ID-MS is based on the high specifi-... 

When the separation is not strictly stoichiometric, a cahhration curve determined from a series of known samples is used. Radioimmunoassay is based on this principle of suhstoichiometric isotope dilution analysis. 

Radionuclides are used in many subdivisions of analytical chemistry (see Table 1). Of major importance are radiotracers in methodological and pathway studies, isotope dilution analysis (IDA), radioimmunoassay, and nuclear activation analysis (AA) (- Activation Analysis) [66]. They are all especially suited to analyze the extremely small amounts of substances encountered in ultra-trace analysis or in trace analysis of microsamples. 

Recently Nexo and Hoffmann-Lucke (2011) reported three different methods devised for measuring holoTC, with reasonably similar results. The first method combined ionic precipitation of transcobalamin and measurement of the amount of vitamin B12 trapped in the precipitate (Begley and Hall 1975). Lindemans et al. (1983) improved this method by using antibodies against transcobalamin rather than ionic separation. The second method, proposed by Ulleland et al. (2002), consisted of measuring trapped vitamin B12 by an isotope dilution assay (holoTC radioimmunoassay, RIA). Refsum et al. (2006) used a third technique, a microbiological method, to measure vitamin B12 levels (Nexo and Hoffmann-Lucke 2011). 

Further development of quantitative methods is likely to be dominated by progress in radioimmunoassay and protein-binding methods. The rapidity with which these techniques have encouraged the demise of the classical isotope dilution and bioassay techniques implies that many drugs and their metabolites will eventually be measured by these methods. Progress along these lines, however, has been relatively slow and there are few instances. 

LC—MS/MS assays for 25-OHD [27] are now commonplace in clinical laboratories, especially larger reference laboratories. Often, the first step in the analysis is a liquid—liquid extraction of nonpolar 25-OHD and a deuterated internal standard from serum into an organic solvent, followed by evaporative concentration and injection into the LC—MS/MS. Additional reported metirods for specimen preparation include manual and online solid-phase extraction and simple protein precipitation with an organic solvent. The advantages of LC—MS/MS assays over traditional radioimmimoassays and more current chemiluminescent immunoassays include the use of an isotope dilution for precise quantitation, as well as the ability to distinguish and separately quantitate 25-hydroxy vitamin D2 and 25-hydroxy vitamin D3. There is considerable controversy as to which method of 25-OHD quantitation is the best, however, since many large scale population studies on vitamin D, such as the Women s Health Initiative (WHl) and the National Health and Nutrition Examination Survey (NHANES), utilized radioimmunoassays [28]. 

Radioimmunoassay is based on the chemical antigen-antibody reaction, which obeys the law of mass action, and on the principle of isotopic dilution. 

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