THE PROBLEM:

A government agency had asked a manufacturer to determine if carbon nanotubes (CNTs) were released from their filtration product during normal use. The product contained both carbon nanotubes and activated carbon particles. We were asked to measure the concentration of carbon nanotubes being released by the product into the liquid that flowed through it.

THE ANALYSIS:

MVA Scientific Consultants received several product units and MVA scientists constructed parallel product operation lines from which a known volume of liquid could be collected at specific flow intervals. The collected liquid samples were filtered through membrane filters and the filters were prepared and analyzed for carbon nanotubes following analytical procedures modified from those commonly used for asbestos fiber analysis. Transmission electron microscopy (TEM) was necessary so that the physical morphology of the particles could be observed and activated carbon and carbon nanotubes could be differentiated.

THE OUTCOME:

During the analyses of the filtered liquid, carbon nanotubes were not observed individually or associated with the carbon-rich particles found on the filters. Government agency review of the data produced by MVA Scientific Consultants determined that carbon nanotubes were not being released from the product at the benchmark level the agency had established for the testing.