BSI 19/30376087 DC:2019 Edition

Small-angle X-ray scattering (SAXS) is a well-established technique that allows structural information to be obtained about inhomogeneities in materials with characteristic lengths typically ranging from 1 nm to 100 nm. Under certain conditions (narrow size distributions, appropriate instrumental configuration, and idealised shape) the limit of 100 nm can be significantly extended. This International Standard specifies a method for the application of SAXS to the estimation of mean particle sizes in dilute dispersions where the interaction and scattering effects between the particles are negligible. This International Standard describes several data evaluation methods: the Guinier approximation, model-based data fitting, Monte-Carlo–based data fitting, the Indirect Fourier Transform method and the Expectation Maximization method. The most appropriate evaluation method shall be selected by the analyst and stated clearly in the report. While the Guinier approximation only provides an estimate for the mean particle diameter, the other methods also give insight in the particle size distribution.