Isotope ratio measurements by LA-ICP

LA-ICP-MS will develop into a dominant solid-state analytical technique in the sensitive bulk analysis of homogeneous non-conducting materials (insulators, ceramics and glasses) in the future. The state-of-the-art, challenges and limitations with respect to isotope ratio measurements by LA-ICP-MS using different instrumentations have been reviewed in reference 131. 

Selected applications in isotope ratio measurements by LA-ICP-MS using different equipment are summarized in Table 8.4.50,126 136... 

Table 8.4 Selected applications in isotope ratio measurements by LA-ICP-MS. 

Table 9.39 Results of determination of uranium concentration and isotope ratio measurements by LA-ICP-SFMS on several urine samples (n = 3).

It is widely accepted that the precision or reproducibility of isotope ratio measurements can be improved dramatically by using an MC instrument. However, further correction or careful procedural protocols are required to also improve the trueness of the resulting isotopic data. There are two major considerations for better quality isotope ratio measurements using LA-ICP-MS analysis the isotope fractionation during the LA and/or ionization process in the ICP, and the contribution of the matrix effect (non-spectral interference) to the mass bias effect. The latter is discussed in Section 4.6. First, the level of isotope fractionation during LA or ionization processes is discussed in this section. 

Figure 8.4 54 Fe/56Fe isotope ratios in selected protein spots of Alzheimer s brain samples measured by LA-ICP- MS (isotopic-enriched 54 Fe spike solution was doped to the gel after 2D gel electrophoresis), (j. Su. Becker et al., Int. ]. Mass Spectrom., 242, 135 (2005). Reproduced with permission of Elsevier.)...

Figure 9.25 Tracer studies on tau protein (a) ID gel, (b) 65Cu/63Cu isotope ratios in gel bands measured by LA-ICP-MS, (c) MALDI-FTICR mass spectrum of splice isoform tau F (). Su. Becker, M. Zoriy, M. Przybylski, ]. S. Becker, ]. Anal. At. Spectrom., 22, 63 (2007). Reproduced by permission of the Royal Society of Chemistry.)...

Becker, J. S. 2002. State-of-the-art and progress in precise and accurate isotope ratio measurements by ICP-MS and LA-ICP-MS—plenary lecture. J Anal Atom Spectrom 17(9), 1172-1185. 

Of all the different mass spectrometric techniques for isotope analysis (such as ICP-MS, LA-ICP-MS, TIMS, GDMS, AMS, SIMS, RIMS and isotope ratio mass spectrometry of gases), the greatest proportion of pubhshed papers today concern ICP-MS with single and multiple ion collection.19 Due to its benefits, ICP-MS has now become a widely accepted method for isotope analysis and allows isotope ratios to be measured in a short time with good accuracy and precision.9,19,75 78 As discussed above, as a powerful and universal tool, ICP-MS has opened up new applications for isotope ratio measurements of elements with a high first ionization potential, which are difficult to analyze with TIMS (such as Mo, Hf, Fe). Of all the heavy metals studied, uranium was favoured by ICP-MS and LA-ICP-MS. 

An analytical procedure has been proposed for precise uranium isotope ratio measurements in a thin uranium layer on a biological surface by LA-ICP-MS using a cooled laser ablation chamber.125 One drop of uranium isotope standard reference materials NIST, 350, NIST 930, of our isotopic laboratory standard CCLU 500 (20p.l, U concentration 200 ng 1) and of uranium with natural isotopic pattern were deposited on the leaf surface and analyzed by LA-ICP-MS at well defined laser crater diameters of 10, 15, 25 and 50 p.m. A precision for measurements of isotope ratios in the range of 2.1-1.0% for 235U/238U in selected isotope standards was observed whereby the precision and the accuracy of isotope ratios compared to the non-cooled laser ablation chamber was improved.125... 

Further applications of LA-MC-ICP-MS using the Plasma 54 by Zr isotope ratio measurements in zircon and baddeleyite samples are described by Hirata.147 The isotope ratios 92Zr/90Zr = 0.333 94 0.000 02 and 96Zr/90Zr = 0.054 63 0.000 01 have been determined on a Merck reagent with a precision of 0.01-0.02% and 0.03-0.04%, respectively. Neither isotopic variation in the... 

Selected apphcations of isotope ratio measurements for plutonium by ICP-MS and LA-ICP-MS are summarized in Table 8.8.97,155,171,181 183... 

Plutonium at a concentration level of 0.3 pgg" 1 in contaminated soil samples was determined directly by LA-ICP-SFMS using the isotope dilution technique and 240Pu/239Pu isotope ratios were measured by Boulyga et al.126... 

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