Tracer compound

Radiochemical tracers, compounds labeled with radioisotopes (qv), have become one of the most powerful tools for detection and analysis in research, and to a limited extent in clinical diagnosis (see Medical IMAGING TECHNOLOGY). A molecule or chemical is labeled using a radioisotope either by substituting a radioactive atom for a corresponding stable atom in the compound, such as substituting for H, for or for P, and for for... 

Decay products of the principal radionuclides used in tracer technology (see Table 1) are not themselves radioactive. Therefore, the primary decomposition events of isotopes in molecules labeled with only one radionuclide / molecule result in unlabeled impurities at a rate proportional to the half-life of the isotope. Eor and H, impurities arising from the decay process are in relatively small amounts. Eor the shorter half-life isotopes the relative amounts of these impurities caused by primary decomposition are larger, but usually not problematic because they are not radioactive and do not interfere with the application of the tracer compounds. Eor multilabeled tritiated compounds the rate of accumulation of labeled impurities owing to tritium decay can be significant. This increases with the number of radioactive atoms per molecule. 

Because exposure to radiation is a health risk, the administration of radioactive isotopes must be monitored and controlled carefully. Isotopes that emit alpha or beta particles are not used for Imaging, because these radiations cause substantial tissue damage. Specificity for a target organ is essential so that the amount of radioactive material can be kept as low as possible. In addition, an Isotope for medical Imaging must have a decay rate that is slow enough to allow time to make and administer the tracer compound, yet fast enough rid the body of radioactivity in as short a time as possible. 

Analysis of the halohydrocarbons, halocarbons, and sulfur hexafluoride is usually achieved by gas chromatography that is equipped with an electron capture detector. Complex metal anions, such as cobalt hexacyanide, are used as nonradioactive tracers in reservoir studies. The cobalt in the tracer compound must be in the complex anion portion of the molecule, because cationic cobalt tends to react with materials in the reservoir, leading to inaccurate analytic information [1226]. 

Uncommon elements may be used as tracer compounds. Tracers are being used increasingly by... 

In the case of a facility that has multiple tanks in close proximity to each other, different tracer compounds can be used so that sample analysis will rapidly identify a specific leaking tank. 

XIV, R = CH3 and C2H5, respectively, Fig. 10b), whereas the sediment contains additional friedelin, i-friedelanol and ursolic acid. Furthermore, the friedelin photoproducts, i.e. dihydroputranjivic acid (3,4-r c<7-friedelan-3-oic acid, XV) and 4a- and 4P-3-norfriedelane (XVI) are dominant sedimentary components. Thus, characterizing photoproducts from terpenoids may provide additional biomarker tracer compounds for environmental studies. 

Tracer compound Physical process or function Typical application... 

P 9.4 Estimating the Retardation of Organic Compounds in an Aquifer from Breakthrough Data of Tracer Compounds... 

Wagener S, Langner M, Hansen U (2012) Spatial and seasonal variations of biogenic tracer compounds in ambient PM10 and PM1 samples in Berlin, Germany. Atmos Environ 47 33-42... 

Experiments were conducted involving the addition of tracer compounds to the propellant, followed by an examination of the discharge particles to determine if any of the particles and which type contained the tracer.173 The tracer was found in primer particles only, which supports the proposition that they should be found dissolved in the oxides and salts originating from the primer and not in the bullet particles. A similar experiment involving the coating of bullets with metals not normally associated with firearms ammunition, followed by examination of the discharge particles, supported the proposition that the bullet material makes a contribution to the primer particles. 

Fluorescent tracer techniques hold the promise of improved accuracy in assessing dermal exposures, as they require no assumptions regarding the distribution of exposure across skin surfaces. However, this approach also has several limitations. First, it requires introduction of the tracer compound into the agricultural spray mix. Secondly, there must be demonstration of a correspondence between pesticide deposition and deposition of the fluorescent compound for the production, such that the fluorescence can indeed be considered a tracer of chemical deposition. Thirdly, range-finding and quality assurance studies may be needed to ensure the accuracy of tracer measurements. Fourthly, when protective clothing is worn by workers, the relative penetration of the pesticide and tracer needs to be characterized. All of these limitations make fluorescent tracer methods technically challenging. 

Water color blocks, washing blue, dye blocks Insulators, collector brushes, carbon contacts Gun powder, flare/tracer compounds, varied uses in ordnance and pyrotechnics... 

To ensure that photolysis is the only loss process for the aldehyde experiments can be carried out in the presence of an excess concentration of a radical scavenger such as cyclohexane. In cases where the high concentration of a scavenger is undesirable, e.g. because it causes saturation in the infrared absorption spectrum, a tracer compound, such as di-n butyl ether, can be used to correct for the measured decay of the aldehyde in order to obtain the j value. Typical starting concentrations used in photolysis experiments at EUPHORE are [aldehyde] = 0.5-1.5 ppmv, [scavenger] = 10-50 ppmv or [tracer] = 0.1-02. ppmv (Wenger et ai, 2004 and Magneron et al, 2002). 

Monitoring of groundwater contaminations caused by a leaking waste deposit landfill using organic tracer compounds ... 

G Gill Street Woburn, MA Fax 781-932-6775 E-mail mstrace ix.netcom.com Internet site www.masstrace.com custom synthesis of tracer compounds labeled with stable isotopes... 

Several hundred organic compounds have been identified in primary organic aerosol emissions. In spite of this these studies have been able to identify compounds representing only 10-40% of the emitted organic mass depending on the source. Even if our knowledge of the molecular composition of OC has increased significantly, the complexity of the mixture is such that tracer compounds are still necessary to unravel the contributions of the various sources. 

A set of tracer compounds have been proposed for the identification and quantification of the contributions of a number of sources to ambient aerosol concentration levels. These sets of compounds are summarized in Table 14.9. For example, cholesterol concentrations can be used to estimate the contribution of meat cooking operations to the ambient OC aerosol in a given area (see Problem 14.1). 

TABLE 14.9 Tracer Compounds for Atmospheric Primary Organic Aerosol Sources... 

Schulz et al. observed that during the cobalt normal-pressure synthesis, 2-propanol and acetone tracer compounds were interconverted by fast hydrogenation/dehydrogen-ation reactions thus, both acetone and 2-propanol initiated chain growth. With either acetone or 2-propanol, propane was found to be one of the major products. 

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