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Journal of Analytical Methods in Chemistry
Volume 2016, Article ID 3834292, 10 pages
http://dx.doi.org/10.1155/2016/3834292
Research Article

Determination of Metal Impurities in Carbon Nanotubes Sampled Using Surface Wipes

1Environmental Health Science and Research Bureau, HECSB, Health Canada, 50 Columbine Driveway, Tunney’s Pasture 0803C, Ottawa, ON, Canada K1A 0K9
2Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, ON, Canada K1N 6N5

Received 11 August 2016; Accepted 12 October 2016

Academic Editor: Ana María Díez-Pascual

Copyright © 2016 Mary-Luyza Avramescu 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.

Abstract

Residual metal impurities in carbon nanotubes (CNTs) provide a means to distinguish CNT from non-CNT sources of elemental carbon in environmental samples. A practical and cost-effective analytical approach is needed to support routine surface monitoring of CNT metal tracers using wipe sampling. Wipe sampling for CNT metal tracers is considered a qualitative indicator of the presence of CNTs, not a quantitative exposure metric. In this study, two digestion approaches (microwave-assisted nitric acid/H2O2 digestion and ultrasonic nitric/HF acid digestion) in conjunction with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) determination were evaluated for their ability to extract metal impurities from CNT particles captured on wipe substrates. Aliquots of different carbon nanotubes (including NIST 2483 single-wall CNT) with and without GhostWipes™ (ASTM E-1792 compliant) were used to compare the performance of the digestion methods. The microwave digestion method accommodated the bulky wipe sample and also eliminated potential ICP-MS signal interferences related to incomplete digestion. Although quantitative recoveries requiring lengthy multistep digestion protocols may be necessary in other applications, the near-total recoveries achieved in the present study for CNT catalyst elements were adequate for identifying surface contamination of CNTs in the workplace using wipe sampling.