August 14, 2009: Standards body ASTM International has updated its guidelines for a common technique to measure nanoparticles in solutions, to now include statistically evaluated data on the measurement precisions achieved by a wide variety of laboratories.

The study, organized by researchers from the National Institute of Standards and Technology (NIST) and the National Cancer Institute’s Nanotechnology Characterization Laboratory, looks at data from 26 different laboratories to provide a benchmark for measuring sizes and size distribution of nanoparticles suspended in fluids, a measurement especially key in bio applications such as cancer therapies where nanoparticle sizes affect cell response, according to NIST materials researcher Vince Hackley, according to a press release. One of these is photon correlation spectroscopy (PCS) or dynamic light scattering, in which a laser beam is passed through a solution, and its scattered light fluctuations measured; that, plus knowing parameters such as the fluid’s viscosity and temperature, can come up with size values for the particles.

That’s the type of work the ATSM standard E2490 aims to support, states Hackley. “The study really assesses, in a sense, how well people can apply these techniques given a fairly well-defined protocol and a well-defined material,” he says. Key is to start with a “well-defined material,” a task helped by NIST’s own recently released standard for biomed research, targeting gold nanoparticles.

The new study requires labs to measure particle size distribution in five samples (three from NIST reference materials and two dendrimer solutions), using not only PCS but also electron- and atomic-force microscopy. Results were factored into precision and bias tables that are now a part of the ASTM standard.