Radiotracer label

Positron emission tomography (PET) is another tomographic technique using radiotracers, labeled with... 

Fowler, S. A., J. La Rosa, M. Heyraud, and W. C. Renfro. 1975. Effect of different radiotracer labelling techniques on radionuclide excretion from marine organisms. Mar. Biol. 30(4) 297-304. 

Besides the application of radiotracer labeling, he has studied many systems with traditional and other combined electrochemical techniques [100-104]. Some of his results are considered fundamental ones, e.g., the application of nickel oxide electrodes for the oxidation of organic species, open-circuit electrochemical... 

Electrochemical quartz crystal microgravimetry AC impedance spectroscopy Spectroelectrochemistry Potentiometry Radiotracer labeling Miscellaneous methods Polythiophene Polyaniline Polyacetylene... 

Synthetic chemical approaches to the preparation of carbon-14 labeled materials iavolve a number of basic building blocks prepared from barium [ CJ-carbonate (2). These are carbon [ C]-dioxide [ CJ-acetjlene [U— C]-ben2ene, where U = uniformly labeled [1- and 2- C]-sodium acetate, [ C]-methyl iodide, [ C]-methanol, sodium [ C]-cyanide, and [ CJ-urea. Many compHcated radiotracers are synthesized from these materials. Some examples are [l- C]-8,ll,14-eicosatrienoic acid [3435-80-1] inoxn. [ CJ-carbon dioxide, [ting-U— C]-phenyhsothiocyanate [77590-93-3] ftom [ " CJ-acetjlene, [7- " C]-norepinephrine [18155-53-8] from [l- " C]-acetic acid, [4- " C]-cholesterol [1976-77-8] from [ " CJ-methyl iodide, [l- " C]-glucose [4005-41-8] from sodium [ " C]-cyanide, and [2- " C]-uracil [626-07-3] [27017-27-2] from [ " C]-urea. All syntheses of the basic radioactive building blocks have been described (4). 

Other methods of sensitive detection of radiotracers have been developed more recently. Eourier transform nmr can be used to detect (nuclear spin 1/2), which has an efficiency of detection - 20% greater than that of H. This technique is useful for ascertaining the position and distribution of tritium in the labeled compound (14). Eield-desorption mass spectrometry (fdms) and other mass spectral techniques can be appHed to detection of nanogram quantities of radiolabeled tracers, and are weU suited for determining the specific activity of these compounds (15). 

Isotope Dilution Assay. An isotope dilution assay for biotin, based on the high affinity of avidin for the ureido group of biotin, compares the binding of radioactive biotin and nonradio active biotin with avidin. This method is sensitive to a level of 1—10 ng biotin (82—84), and the radiotracers typically used are p C]biotin (83), [3H]biotin (84,85) or an I-labeled biotin derivative (86). A variation of this approach uses I-labeled avidin (87) for the assay. 

Fowler, J S, Wolf, A P The Synthesis of Carbon-II, Fluorine 18 and Nitrogen 13 Labeled Radiotracers for Biomedical Applications, Mono graph NAS-NS-3601, Technical Information Center, U S Department of Energy... 

A correlation between the amount of adsorbed ions and the electrode potential, in particular E. , has been identified apparently for the first time by Frumkin and Obrutschewa [26Fru]. A minimum of ionic adsorption was found at E, this is equivalent to the absence of specific adsorption at Ep c- The measurement of the amount of adsorbed ions was performed by measuring the ionic concentration in the solution as a function of the electrode potential or by measuring the surface concentration of adsorbed ions by e.g. radiotracer techniques (see also 4.2). (Data obtained with this method are labelled lA). 

Applications Radiotracer measurements, which combine high sensitivity and specificity with poor spatial resolution, have been used for migration testing. For example, studies have been made on HDPE, PP and HIPS to determine effects of manufacturing conditions on migration of AOs from plastic products into a test fat [443]. Labelled antioxidant was determined radio-analytically after 10 days at 40 °C. Acosta and Sas-tre [444] have used radioactive tracer methods for the determination of styrene ethyl acrylate in a styrene ethyl acrylate copolymer. 

Mineral Oil Hydraulic Fluids. Absorption of a mineral oil in an emulsion was apparently very slow in female rats injected subcutaneously with 0.1 mL and in squirrel monkeys injected intramuscularly with 0.3 mL (Bollinger 1970). The emulsion contained 1 volume mannide monoleate, 9 volumes mineral oil, and 9 volumes water [14C]labeled hexadecane, a major component of the mineral oil, was added to the emulsion as a radiotracer. At 1 week and 10 months after treatment, radioactivity remaining at the sites of injection accounted for 85-99% and 25-33%, respectively, of the administered radioactivity. 

This synthetic approach is attractive because the trialkyltin group can be removed rapidly and cleanly under mild reaction conditions and because the expensive label, which invariably has a short half-life, is not added until the last step in the synthesis. Because of these advantages, this synthetic approach has been widely used by several research groups to prepare radiohalogenated labelled hormones, neurohormones, neurotransmitter receptors, etc. for radiotracer and therepeutic uses123. 

The resulting device has demonstrated both FDG and FLT labelling at yields of 98% and 90%, respectively, in 100 s compared to typical macro-scale labelling of 65% in 45 min for FDG and 30% in 90 min for FLT. The use of acetonitrile, DMSO and HC1 have shown no degrading effect on the system. Extremely efficient labelling illustrates the effectiveness of flow-based micro-reactors for PET biomarker synthesis. Multiple biomarkers can be produced in 1-2 min, while using only micro-litres of precursor and can revolutionise the production of radiotracers. Small reaction volumes, improved yields, and the ability to synthesise small quantities of a variety of new compounds will allow preclinical and clinical evaluation of new PET agents with potential for clinical utilisation. 

The pulsed field gradient nuclear magnetic resonance (PFG NMR) technique is experimentally distinct from the radiotracer technique but the principle is very similar. A fraction of the nuclei of each constituent is labelled by flipping their spins and monitoring the diffusion of these species. Both techniques are influenced by the presence of neutral associates unlike the Hittorf/Tubandt method. 

---