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Journal of Automated Methods and Management in Chemistry
Volume 2008, Article ID 504092, 6 pages
Research Article

The Effect of Isotopic Composition on the Uncertainty of Routine Metal Mass Concentration Measurements in Ambient Air

Analytical Science Team, National Physical Laboratory, Teddington, Middlesex TW11 0LW, UK

Received 20 October 2008; Accepted 9 December 2008

Academic Editor: Peter Stockwell

Copyright © 2008 Richard J. C. Brown et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The main sources of uncertainty encountered during the analysis of the mass concentration of metals in ambient air as part of the operation of the UK Heavy Metals Monitoring Network are presented. It is observed that the uncertainty contribution from possible variation in the isotopic composition of the sample depends on the element in question, but can be significant (e.g., for Pb, Cd, and Hg). The working curve method for the ICP-MS analysis of metals in solution, with a low resolution, high throughput instrument measuring at one 𝑚/𝑧 ratio per element, relies on the relative abundance of the isotopes under consideration being the same in both the sample and the calibration solution. Calculation of the uncertainty in this analysis assumes that the isotopic composition variation within the sample and calibration solution is limited to a defined range. Therefore, in order to confirm the validity of this quantification methodology and its uncertainty budget, the isotopic composition of the calibration standards used for quantification has been determined. The results of this analysis are presented here.