Isotope ratios, use

In isotope dilution inductively coupled plasma-mass spectrometry (ID-ICP-MS) the spike, the unspiked and a spiked sample are measured by ICP-MS in order to determine the isotope ratio. Using this technique, more precise and accurate results can be obtained than by using a calibration graph or by standard addition. This is due to elimination of various systematic errors. Isotopes behave identically in most chemical and physical processes. Signal suppression and enhancement due to the matrix in ICP-MS affects both isotopes equally. The same holds for most long-term instrumental fluctuations and drift. Accuracy and precision obtained with ID-ICP-QMS are better than with other ICP-QMS calibration... 

The previous equations do not require that the isotopic ratio used for normalization (x-axis) and the ratio to be measured (y-axis) have to be for the same element. It is therefore possible to normalize the isotopic composition of Cu to that of a standard Zn solution without any assumption made on the particular mass-fractionation law. The original formulation of this property by Longerich et al. (1987) calls for identical isotopic fractionation factors for the two elements, but this is not at all a necessary constraint and Albarede et al. (2004) show that, in fact, this very assumption may lead to significant errors. For a Cu sample mixed with a Zn standard, in which the Zn/ Zn ratio of the standard solution is used for normalization, we obtain the expression ... 

The fractionation laws relating two or more isotope ratios are described by a relationship between the fractionation factors for the isotope ratios. Using Mg as an example, the three isotopes Mg, Mg, and Mg define two fractionation factors... 

M. W. Todd, J. Glasser, A. A. Kachanov, B. A. Paldus, T. G. Spence, and R. N. Zare, "Stable Isotope Ratios Using Cavity Ring-Down Spectroscopy Determination of, C/I2C for Carbon Dioxide In Human Breath,"... 

Furutu, N.J. (1991) Optimization of the mass scanning rate for the determination of lead isotope ratios using an inductively coupled plasma mass spectrometer J. Anal. Atomic Spectrom. 6, 199-203. 

The increase of the isotope ratio Ca/ Ca and Ca/ Ca in the solution compared with the intial isotope ratio using [2.2.1] means that the Ca -cryptate complex is enriched in the exchanger resin. As one can see from the results in Table 16, the effect is inverse for [2.2.2]. Of course, one has to take into account that the analyzed isotopic separations are in the range of the measuring errors. 

The orientation of the HD molecule, on the other hand, has been found to have little effect on the isotope ratio. George and Suplinskas [123] have calculated the isotope ratio using their kinematic model [115] for the reaction with and without taking this effect into account. Both calculations have given equally reasonable predictions of the isotope ratio at Ar" energies higher than 30 eV (LAB). Below 30 eV, their results have no quantitative significance. 

Kendall, C. E. Grim, 1990. Combustion tube method for measurement of nitrogen isotope ratios using calcium oxide for total removal of carbon dioxide and water. Anal. Chem. 62 526-529. 

Clearly, these considerations necessitated initial chemical work using appropriate standards and various isotopic geochemical laboratories employ different reference gases or working standards in order to measure relative isotopic ratios using mass spectrometers. In Table 16.1 there is a list of the most important isotopes involved. 

Taylor, R.N., Wameke, T., Milton, J.A., Croudace, I.W., Warwick, P.E., and Nesbitt, R.W. (2003) Multiple ion counting determination of plutonium isotope ratios using multi-collector ICPMS, J. Anal. At. Spectrom., 18, 480-484. 

The isotopic abundances of the tracee or the tracer can be obtained from measured isotope ratios using Eqs. (16.2) and (16.3), while atomic masses can be taken from the literature (10]. Based on IDMS principles, measured isotope ratios can be converted into tracer to tracee ratios in the sample analyzed. The amount of tracee can then be calculated if the amount of tracer in the sample is known. The latter can be determined either by IDMS using an additional tracer or by non-IDMS techniques for quantitative analysis employing external calibration or standard addition techniques. 

Becker, J.S., Fiillner, K., Seeling, U.D., Fornalczyk, G., and Kuhn, A.J. (2008) Measuring magnesium, calcium and potassium isotope ratios using ICP-QMS with an octopole collision cell in tracer studies of nutrient uptake and translocation in plants. Anal. Bioanal. Chem., 390, 571-578. 

Hosoe, M., Fujii, Y., and Okamoto, M. (1988) Mass-spectrometric measurements of copper isotopic-ratios using low-temperature thermal ionization. Anal. Chem., 60, 1812-1815. 

Dzurko et al. [12] determined compound-spedfic Hg isotope ratios using GC interfaced with MC-ICP-MS (Table 17.1). The procedure consists of (i) species extraction based on ethylation, followed by preconcentration of the species thus obtained on a Tenax trap, (ii) thermal desorption of these Hg species and separation using a home-made GC unit, and (iii) registration of the isotope ratios in Hg species using a Neptune MC-ICP-MS instrument. Thallium was introduced... 

The determination of PN is also performed in concomitance to the automated bulk sample analysis of isotope ratio, using elemental analyzers coupled with isotopic... 

Doucet et described the determination of isotope ratios using LIBS in air at atmospheric pressure for partially resolved uranium-235-uranium-238 and hydrogen-deuterium isotope shift lines. A PLSl regression model could accurately predict the isotopic ratio under conditions where the application of traditional univariate approaches for hydrogen and uranium would not be achievable. 

F. R. Doucet, G. Lithgow, R. Kosierb, P. Bouchard and M. Sabsabi, Determination of isotope ratios using Laser-Induced Breakdown Spectroscopy in ambient air at atmospheric pressure for nuclear forensics, J. Anal. At. Spectrom., 2011, 26(3), 536-541. 

Roehl, R., Gomez,]., and Woodhouse, L. R. (1995). Correction of mass bias drift in inductively coupled plasma mass spectrometry measurements of zinc isotope ratios using gallium as an isotope ratio internal standard./. Ana/. Xt. Spectrom. 10(1), 15. 

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