Scientists working at Malvern Instruments have published experimental protocols for measuring hydrodynamic particle diameters of less than 1nm, with a precision of 0.1nm.
These protocols were presented in a paper called 'Measuring Sub Nanometre Sizes using Dynamic Light Scattering', which appeared in the Journal of Nanoparticle Research (volume 10, number five, May 2008).
The researchers used a Malvern Zetasizer particle-characterisation system, which uses dynamic light scattering (DLS) for particle-size measurement.
Its optical configuration, comprising of a sensitive detector combined with an optimised fibre-optic configuration, was critical for the sensitivity achieved.
The paper is currently available online, with open access.
A related application note can be downloaded for free from Malvern's website.
The technology is useful for drug development, in which proteins are often used as active pharmaceutical ingredients and there is a growing need for techniques sensitive enough to characterise particles in the nanometre size range.
Sucrose was chosen as an extreme example, to give confidence in the system and technology at the limits of the specification.
DLS analyses time-dependent fluctuations in the intensity of scattered laser light to measure the diffusion co-efficient and particle size.
This study research shows that, with careful sample preparation and an appropriate optical configuration, the Zetasizer Nano S can accurately measure particle size at the sub-nanometre scale.
These results are significant for applications requiring quality control of small molecules.
