1.1 This test method is an analytical procedure using transmission electron microscopy (TEM) for the determination of the concentration of carbon nanotube structures in ambient atmospheres. 1.1.1 This test method is suitable for determination of nanotubes in both ambient (outdoor) and building atmospheres. 1.2 This test method is defined for polycarbonate capillary-pore filters or cellulose ester (mixed esters of cellulose) filters through which a known volume of air has been drawn and for blank filters. 1.3 The upper range of concentrations that can be determined by this test method is based on the particulate loading on the filter. The maximum nanotube particle loading that can be analyzed is 7000 nanotube structures/mm2. The air concentration represented by this value is a function of the volume of air sampled and the effective area of the filter analyzed. For example, with a 10-L sample on a 385-mm2 filter, the maximum concentration is 270 000 nanotube structures per litre of air (0.27 nanotube structures per cubic metre). The lower range of concentrations that can be determined by this test method is dependent on the amount of air that can be collected without overloading the filter with particulate and the amount of filter that is analyzed. For example, with a 1000-L sample on a 385-mm2 filter on which 0.2 mm2 is analyzed, the concentration determined if five nanotube structures were detected is approximately ten nanotube structures per litre of air (0.000 01 nanotube structure per cubic metre). Collection of more air volume or the analysis of more of the filter area would result in a lower value. 1.3.1 There is no lower limit to the dimensions of carbon nanotubes that can be detected. In practice, microscopists vary in their ability to detect very small carbon nanotubes. Therefore, a minimum length of 250 nm has been defined as the shortest nanotube to be incorporated in the reported results. 1.4 The direct analytical method cannot be used if the general particulate matter loading of the sample collection filter as analyzed exceeds approximately 25 % coverage of the collection filter by particulate matter. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Currently, no standard method exists for the analysis of carbon nanotubes collected from air membrane filters. This test method will be used by those attempting to monitor for nanotubes in the air both occupationally and in the ambient environment.
Keywordsair; ambient air; nanotubes; electron microscopy; indoor atmospheres; microscopy
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top