Centrifugal liquid sedimentation particle testing standards are published by ISO. This includes the ISO 13318 series on determination of particle size distribution by centrifugal liquid sedimentation methods. This includes topics from general principles, photocentrifuge methods, and centrifugal x-ray methods.
This document specifies the principles of particle size analysis by centrifugal liquid sedimentation (CLS). It also: — defines the relevant terms; — describes the various measurement techniques; — gives guidance for sample preparation, conducting measurements as well as data analysis; — establishes rules for method validation, determination of the uncertainty budget as well as representation of results. An important part of this document deals with the derivation of particle size distributions from CLS data, including discussions on: — the impact of Brownian motion; — the parallel determination of particle concentrations; — the working range with respect to size and concentration; —the handling of non-spherical and porous particles. This document applies to samples composed of dispersions of low particle concentration, so that the particles’ motion can be considered as that of fully isolated particles. This document does not cover particle migration by gravity, electric or magnetic forces. It also does not cover deriving particle properties other than size, sedimentation velocity and sedimentation coefficient. NOTE This document can involve hazardous materials, operations and equipment. It does not purport to address all the safety problems associated with its use. Regulations regarding explosion-proof analysers can apply when examining volatile liquids with a low flash point. It is the responsibility of the user of this document to establish appropriate safety and health practices and to determine the applicability of the regulatory limitations prior to its use.
ISO 13318-2:2007 covers methods for determining the particle size distribution of particulate materials by means of centrifugal sedimentation in a liquid. Solids concentrations are determined by the transmission of a light beam. The resulting signal enables conversion to a particle size distribution. The method of determining the particle size distribution described in ISO 13318-2:2007 is applicable to powders that can be dispersed in liquids, powders that are present in slurry form and some emulsions. Typical particle size range for analysis is from about 0,1 µm to 5 µm. The method is applicable to powders in which all particles have the same density and comparable shapes and do not undergo chemical or physical change in the suspension liquid. It is usually necessary that the particles have a density higher than that of the liquid.
ISO 13318-3:2004 describes a method for determining the particle size distributions of homogeneous particulate material using centrifugal sedimentation in a liquid. Solids concentrations are determined by the attenuation of an X-ray beam. The resulting signal enables conversion to a particle size distribution. The method of determining the particle size distribution described in this standard is applicable to powders which can be dispersed in liquids or powders which are present in slurry form. The typical particle size range for analysis is from 0,1 m to 5 m. The method is applicable to powders in which all particles have the same effective density, chemical composition and comparable shapes. Materials possessing elements with an atomic number greater than about 12 can be expected to produce adequate X-ray opacity. Particles should not undergo chemical or physical change in the suspension liquid. It is necessary that the particles have a higher density than that of the liquid.
