本文件规定了小角X射线散射（SAXS）用于估算1nm至100nm粒径范围内平均粒径的方法。它适用于粒子之间的相互作用和散射效应可以忽略的稀释分散体。本文介绍了几种数据评估方法:吉尼尔近似法、基于模型的数据拟合、蒙特卡罗？基于数据拟合，采用了间接傅里叶变换法和期望最大化法。分析员将选择最合适的评估方法，并在报告中明确说明。虽然吉尼尔近似法仅提供平均粒径的估计值，但其他方法也提供了对粒径分布的洞察。

This document specifies a method for the application of small-angle X-ray scattering (SAXS) to the estimation of mean particle sizes in the 1 nm to 100 nm size range. It is applicable in dilute dispersions where the interaction and scattering effects between the particles are negligible. This document 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 is intended to 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.