High-precision isotope ratio measurement

Being a valuable isotope analytical technique in routine work for high precision isotope ratio measurements, TIMS is applied in many laboratories worldwide for isotope ratio measurements especially for elements with ionization potentials < 7 eV,7 such as alkali and earth alkali elements, rare earth elements (REE), uranium and plutonium. It is advantageous that the interference problem occurs relatively seldom in TIMS, especially if the negative thermal ionization technique for elements and molecules with electron affinities > 2eV (Ir, W, Os, Re, Pt, Cl and Br) is applied. TIMS with multiple ion collectors achieves a precision of up to 0.001 % thus permitting the study... 

Multiple Ion Collector Mass Spectrometry for High Precision Isotope Ratio Measurements... 

High-precision isotopic ratio measurements with MC-ICP-MS have now been made on a large range of elements with high first ionization potential, including Cu and Zn (Blichert-Toft et al., 1996 Marshal et al., 1997) Ga and Ge (Hirata, 1997) Mo (Lee and Halliday, 1995a) Ru, Pd, and Ag (Rehkamper and... 

However, elemental ratios can be fractionated due to gas loss from the samples through microfractures or crystal imperfections, which is governed by differences in molecular volumes (Craig et al. 1988 Bender et al. 1995). This process does not significantly affect isotope ratios. For this reason, much of the work on fractionation of trapped gases in ice has focused on high-precision isotope ratio measurements. 

Allen, L. A. Georgitis, S.J. High Precision Isotope Ratio Measurements by the LECO Renaissance TOF-ICP-MS, LECO Technical Brief, available at www.leco.com. 

Truong QS, Keeffe R, Ellacott T, Desson K, Herber N (2001) In IAEA symposium on international safeguards, IAEA-SM-367/8/08/P Tuttas D, Schwieters JB, Quaas N, Bouman C (1998) Improvements in TIMS high precision isotope ratio measurements for small sample sizes. Application note 30136, Thermo Eisher Scientific, Bremen Tuttas D, Schwieters JB, Bouman C, Deerberg M (2005) New compact discrete dynode multipliers integrated into the thermo scientific TRITON variable multicollector array. Application note 30192, Thermo Fisher Scientific, Bremen United Nations Security Council (1991) Text of UNSC Resolution 687. Available at http //www.fris.org/ news/un/iraq/sres/sres0687.htm... 

High-precision isotope ratio measurements require critical control of the background and interference suppression using high mass resolution is regarded as the most unambiguous way to eliminate spectral interferences. 

Hintelmann, H. and Lu, S.Y. (2003) High precision isotope ratio measurements of mercury isotopes in cinnabar ores using multicollector inductively coupled plasma mass spectrometry. Analyst, 128, 635-638. 

There also is a small dependence of sensitivity on the mass of the analyte ion being measured. The relationship is a complex combination originating from many sources. For this reason it is universally determined empirically. This effect is of particular importance in isotope ratio measurements. Typically, when highly precise isotope ratio measurements are required, a known certified isotope standard is used to establish the mass bias, which is then used to correct the sample ratio. Usually this technique is only appropriate over a small mass range. 

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