Geochronology isotope ratio measurements

Instrumental developments (e.g., of sector field instruments with multiple ion collection, introduced in 1992, or the insertion of collision and reaction cells in order to reduce disturbing isobaric interferences), the progress in applications for ultratrace analysis, also in combination with on line hyphenated separation techniques (HPLC, CE), especially routine capability as well as decreasing price and user friendly maintenance mean that sales are increasing by 10 % every year. To improve the analytical performance of ICP mass spectrometers for precise isotope ratio measurements (e.g., for geochronology or for the study of fine isotope variation in nature) powerful instrumentation with high mass dispersion and multiple ion collector systems instead of single ion collection are commercially available on the analytical market. 

For direct isotope ratio measurements on solid samples, laser ablation ICP-MS (LA-ICP-MS) is applied to an increasing extent in geology, geochronology, biology and environmental research.6... 

Applications of Isotope Ratio Measurements in Geochemistry and Geochronology... 

Isotope dilution mass spectrometry (ID-MS) is widely accepted as a quantification procedure of proven accuracy in elemental analysis and isotope ratio measurements [4]. Several areas of research in nuclear science, geochronology, medicinal chemistry, environmental science, and agricultural science have benefited from this technique. ID-MS is applicable to all elements that have at least two stable isotopes. Monoisotopic elements can be analyzed only if they have a long-lived natural or artificial radioisotope. For example, iodine and thorium have been determined with spikes of the long-lived isotopes 29i and 25 Th, respectively [44]. TI-MS and ICP-MS are the methods of choice for accurate ID-MS analysis. ICP-MS has the advantage that several elements can be analyzed simnltaneously under the same experimental conditions. Other ionization techniqnes discussed in this chapter have also been coupled with ID-MS. 

Geochronology for age dating of minerals is a major field in earth sciences, includes measurements of isotope ratios and requires advanced sensitive, precise and accurate mass spectrometric techniques. The determination of the age of the Earth has been of significant interest for hundreds... 

For example, accurate and reproducible U and Th isotope ratios for the geochronology of carbonates were obtained when analyzing small sample sizes (0.05-0.34 ng of Th measured by MC-ICP-MS in comparison to 0.3-1.4 ng Th for TIMS to obtain comparable precision).An analytical technique for the measurement of Ra- °Th- U disequilibria in volcanic rocks is MC-ICP-MS. MC-ICP-MS, which is much less time-consuming than TIMS, also yields a better precision (2-3 times) for Th/ °Th isotope ratios, was proposed by Pietruska et... 

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