Parkinson, I. J.; Bonnand, P.; Pearce, C. R. and Fehr, M.
(2010).
URL:  http://www.agu.org/cgibin/wais?ss=V51B2190 

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Abstract
It is now well established that instrumental mass fractionation on MCICPMS instruments does not always adhere to the exponential mass fractionation law and can be better described by the generalised power law (GPL). However, existing doublespike equations assume exponential mass fractionation behaviour. Therefore, deviations from the exponential law become important because of the large amount of fractionation in the MCICPMS. We have collected Cr and Mo doublespike standard data over a number of years. These data plot with small but measurable mass dependent differences from zero per mil, which vary between analytical sessions. We interpret that these deviations are due to small variations in the mass fractionation behaviour of the MCICPMS and are related to differences in the type of nebuliser and cone geometry. The GPL relies on deriving a value for the exponent term, n, and its value can be derived from the slope of the natural logarithms of the measured isotope ratios. However, the instrumental mass fractionation on modern MCICPMS is very stable within an analytical session, so the spread in the isotope ratios of a standard is not very large, making it difficult to derive any statistically valid information on the value of the slope. For Cr, which only has four isotopes, we adopt a numerical technique for deriving the value of n. Offsets in the δ^{53}Cr values can be reproduced by varying n between 0.058 and 0.090. Molybdenum has seven isotopes and is therefore possible to incorporate the GPL into the doublespike equations and solve directly for n, using four isotope ratios. The advantage of this technique is that allows the correct mass fractionation behavior to be applied to standards and samples within and between analytical sessions. This provides a means to generating highprecision data without recourse to ad hoc daily corrections.
Item Type:  Conference Item  

Copyright Holders:  2010 American Geophysical Union  
Project Funding Details: 


Extra Information:  American Geophysical Union, Fall Meeting 2010, abstract #V51B2190  
Academic Unit/Department:  Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences Faculty of Science, Technology, Engineering and Mathematics (STEM) 

Interdisciplinary Research Centre:  Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)  
Related URLs:  
Item ID:  30763  
Depositing User:  Ian Parkinson  
Date Deposited:  06 Jan 2012 10:04  
Last Modified:  02 Aug 2016 14:08  
URI:  http://oro.open.ac.uk/id/eprint/30763  
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