S. Barton, J.-L. Brousseau
Keywords: nanoparticle, sizing, SAXS, small angle X-ray
Summary:Future regulatory actions on Nanoparticles will likely require accurate reporting of particle sizes used in food, cosmetic and related products on a worldwide basis. While Light Scattering is often the default sizing tool, the resulting accuracy and precision is compromised for particle dimensions below 20nm. Small Angle X-ray Scattering (SAXS) demonstrably overcomes this limitation. We will show that SAXS provides accurate particle sizing distribution without any assumptions about the mathematical form taken by the distribution. The strength of the method is based on an Expectation Maximization algorithm that incorporates the measured characteristics of the x-ray beam in an automated fashion; this leads to a smooth workflow from sample loading to size distribution report. The methods described are appropriate for particle sizes from c.a. 340nm down to a few nm, including multimodal distributions. Most significantly, SAXS substantially extends the practicality of particle sizing to dry powders as well as solutions. This presentation will describe the basic relationship between scattering and particle size, with real-world examples.