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Journal of Automated Methods and Management in Chemistry
Volume 2008 (2008), Article ID 179498, 14 pages
http://dx.doi.org/10.1155/2008/179498
Research Article

A Study of the Critical Uncertainty Contributions in the Analysis of PCBs in Ambient Air

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

Received 21 December 2007; Accepted 29 April 2008

Academic Editor: Peter Stockwell

Copyright © 2008 Andrew S. Brown and Richard J. C. Brown. 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.

Abstract

The measurement of polychlorinated biphenyls (PCBs) in ambient air requires a complex, multistep sample preparation procedure prior to analysis by gas chromatography—mass spectrometry (GC-MS). Although routine analytical laboratories regularly carry out these measurements, they are often undertaken with little regard to the accurate calculation of measurement uncertainty, or appreciation of the sensitivity of the accuracy of the measurement to each step of the analysis. A measurement equation is developed for this analysis, and the contributory sources to the overall uncertainty when preparing calibration standards and other solutions by gravimetric and volumetric approaches are discussed and compared. For the example analysis presented, it is found that the uncertainty of the measurement is dominated by the repeatability of the GC-MS analysis and suggested that volumetric (as opposed to gravimetric) preparation of solutions does not adversely affect the overall uncertainty. The methodology presented in this work can also be applied to analogous methods for similar analytes, for example, those used to measure polycyclic aromatic hydrocarbons (PAHs), pesticides, dioxins, or furans in ambient air.