AS 5009.1:2003 pdf free.Determination of particle size distribution by centrifugal liquid sedimentation methods Part 1: General principles and guidelines.
This correction is usually applied in the equipment software. The value of E is unity for large particles, rising to 2 as the particles pass through the Mie scattering region (about 0,5 him), and rapidly reducing as the particle size decreases into the Rayleigh scattering region (see reference [1] in the bibliography).
If E is assumed constant, then the method may be used as a comparison method only as there may be substantial errors in the 1 .tm size range. The value of E may be evaluated from theory or determined experimentally. Note that the value of the extinction coefficient depends on the wavelength of the light and can also depend on the detector configuration. Consequently, exact determinations of the extinction coefficient are not readily determined. For practical purposes, a value of unity might be assumed and should be stated. If an assumed correction is made by the manufacturer of the apparatus, then this should be stated.
The requirement for extinction coefficient corrections also applies to photosedimentation used in the homogeneous method.
4.3.3 Homogeneous suspension
The homogeneous technique is limited because of approximations which need to be made in the calculation of the results (see reference [3] in the bibliography).
4.3.3.1 Photosedimentation method
In the photosedimentation method, the extinction coefficient corrections detailed in 4.3.2.1 are also required in the homogeneous method.
4.3.3.2 Centrifugal X-ray method
In the centrifugal X-ray method, the attenuation of the X-ray beam is directly proportional to the mass of sample present in the beam and the result is presented automatically. The centrifugal X-ray method is used only in the homogeneous mode due to the requirement for a higher sample concentration than would be feasible using a line- start method.
4.3.3.3 Radial dilution correction
If two monosized spheres are released twenty radii apart at the surface of a gravity sedimentation apparatus, they will remain evenly spaced as they settle. If the same spheres are placed a similar distance apart on the inner surface of a centrifugal sedimentation apparatus, they will become more widely separated as they settle, since they sediment along radial lines. This effect leads to a dilution of the particles as they settle outwards in the centrifuge. The dilution is of concern in the homogeneous mode, since particles of the same diameter commence the analysis at different originating radii; it is of negligible significance in a line-start, since all particle sizes have effectively the same originating radius.AS 5009.1 pdf download.