Isotope dilution -TIMS technique

Isotope Dilution Mass Spectrometry (IDMS). Lead concentrations are only approximated with any analytical technique, since there is no method that can measure the true concentration of any element in any matrix. The most accurate concentration measurements are made with definitive methods, including isotope dilution mass spectrometry (IDMS) using TIMS. Isotope dilution TIMS is considered the definitive method because it is a yield-independent method of analysis, extremely sensitive, and precise (Webster 1960). The analysis is capable of distinguishing lead from false... 

An interesting approach is the application of multiple ion collector mass spectrometry (MC-TIMS and MC-ICP-MS) for the determination of Cd and T1 in high purity zinc metal after trace matrix separation by the certification of reference materials from the Bureau Communie de Reference (BCR).29 Accurate and precise element concentrations in high purity zinc metal have been obtained with both mass spectrometric techniques via precise isotope ratio measurements using the isotope dilution strategy the analytical data. 

Some of the most robust constraints on the tectonic provenance of greenstone belt successions come from U-Pb zircon geochronology and several examples have already been discussed. Ideally, ID-TIMS and SHRIMP techniques are applied in parallel, combining the superior precision (e.g. 1 Ma) of isotope dilution single grain analyses with the high spatial resolution and rapid... 

Isotope dilution as a quantitative technique for elemental analysis was first applied by Reynolds, in 1950, to determine the amounts of decay products after neutron irradiation of Cu, Br , Br, and I. TIMS was the mainstay of this type of analysis for many years until the advent of inductively coupled plasma mass spectrometry (ICP-MS), which allows more rapid determination of a wider range of elements. The technique of IDA is traceable to the mole and so is the method of choice whenever a high... 

Despite considerable improvements to the isotope dilution (ID)-TIMS technique to reduce the amount and size of the analyzed zircon grains, the minimum volume investigated by this method is about the size of a rather large single mineral grain (-100-200 tun in length). 

As seen in the specific examples given later, numerous analytical methods are used for the determination of uranium in environmental samples. The most popular among them are ICPMS and alpha spectrometry, but neutron activation analysis, gamma spectrometry, and XRF are often deployed and even simple spectrophoto-metric (like colorimetric aresnazo-III) techniques are sometimes still used. For the precise determination of total uranium and its isotopic composition, isotope dilution (ID) methods can be used. One example is a comparison of ID-TIMS and ID-SIMS for isotope ratios in soil standards where two separation and preconcentration chromatographic techniques were also compared (Adriaens et al. 1992). 

Thermal ionization mass spectrometry (TIMS) is a sensitive mass spectrometric technique that has been deployed in some cases to measure trace amounts of uranium in urine and its isotopic composition (Kelly et al. 1987). The authors report measurement of one freeze-dried urine standard sample (SRM 2670) and two actual urine samples collected from children. For TIMS measurements, chemical separation has to be performed prior to the analysis. In an earlier work by the same author (Kelly and Fassett 1983), a spike of was used to implement isotope dilution measurements of picogram quantities of uranium in biological tissues. As mentioned earlier, a single urine sample tested by TIMS gave 3.4 ng L (Wrenn et al. 1992). 

Ghidan, O.Y. and Loss, R.D. (2010) Accurate and precise elemental abundance of zinc in reference materials by an isotope dilution mass spectrometry TIMS technique. 

The advantages of lead concentration and isotopic composition measurements by TIMS have established an important niche for this technique in research. This has occurred in spite of the relatively high costs of the instrumentation and supplies, expertise required for analyses and equipment maintenance, and the time required for TIMS measurements (see discussions in the isotope dilution and the isotopic composition measurement sections following). Coincidentally, measurements by TIMS have benefited from recent advances that have substantially lowered the costs of the instrumentation, dramatically simplified the analyses, and greatly accelerated the rate of analysis (e.g., the development of multicollector instruments and multisample turrets). 

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