Silicon isotope ratio measurements

Van den Boom et al.150 have reported on the determination of silicon isotope ratio measurements in silicate materials by MC-ICP-MS (at a mass resolution of 2500 to resolve isobaric interferences) after sodium hydroxide sample digestion and purification of silicon. 829Si and 830Si have been determined for several silicon isotope standard reference materials. A precision for 830Si of 0.18-0.41 %o was achieved. Precise and accurate measurements of isotope ratios on transient signals by HPLC-MC-ICP-MS for nuclear application was performed by Giinther-Leopold et al.151... 

Silicon isotope ratios have been generally measured by fluorination (Douthitt 1982 Ding et al. 1996). However, the method is time consuming and potentially hazardous, therefore, more recently MC-ICP-MS techniques have been introduced (Cardinal et al. 2003 Engstrom et al. 2006). Determinations with SIMS have been carried out by Robert and Chaussidon (2006). Very recently, Chmeleff et al. (2008) have shown that a UV-femtosecond laser ablation system coupled with MC-ICP-MS gives S Si and 5 °Si-values with very high precision. 

Betti (1996) and co-workers used GD-MS for sample screening in isotopic measurements of zirconium, silicon, lithium, boron, uranium, and plutonium in nuclear samples. The results obtained from the GD-MS were compared with results from thermal ionization mass spectrometry (TIMS). For boron and lithium concentrations from //g/g to ng/g levels, isotopic ratios determined by GD-MS were comparable to TIMS in terms of accuracy and precision. Uranium isotopic ratios determined by GD-MS were also in good agreement with values measured by TIMS with regards to accuracy. Chartier et al. (1999) used GD-MS to analyze erbium and uranium in molybdenum-uranium fuel samples. The ratio of 166Er to 238U was then compared to numbers determined by thermal ionization mass spectrometry. The ratio of erbium to uranium was accurate to within 3% of the number determined by TIMS. 

The first few decades of space exploration went by without any MS better than m/Am 4 because understanding the solar wind flow, its density, its pressure, or its temperature did not require mass resolution. Not until 1984 did a space MS fly with a resolution of about 10 [10], and it was 1994 before that increased to 100 [11], Suddenly for the first time, the solar wind isotopes of carbon, oxygen, magnesium, silicon, and iron were known, and the models could be tested. Even then, space MS had difficulty measuring rare isotopes, so that it wasn t until 2005 that solar wind samples were returned to Earth inside ultra-pure silicon wafers (the ill-fated Genesis mission [12]) to determine the important triple ratios of ieO 170 lsO. 

Similarly, rates of cleavage of the silicon compounds (165)-(168) by methanolic NaOMe have been measured (76JCS(P2)925). Isotope effects (Kuboh/KMeoD) and the ratio of products (ArH/ArD) in 1 1 MeOH-MeOD have been determined. From these values it is clear... 

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