Scope

This method is for determining the particle size distribution of powders and slurries using laser light scattering. Most applications are for particle sizes in the 1 to 100 μm range, but the instrument is capable of measuring particles from 0.02 to 2800 μm. Samples are analyzed as received or prepared using sonication to disperse agglomerated particles.

Outline of Method

Forward light scattering is used as the basis for measurement of particle size distribution. The instrument incorporates three lasers to measure the particles over the entire size range. A beam of laser light is projected through a circulating stream of particles and the intensity of the resultant diffraction patterns is measured by a photodetector. The intensity of the detected light at various angles is proportional to the number and size of the particles. The diffraction patterns are processed using optical models selected by the operator. The particle size distribution is presented in histogram format. The data are also summarized to include mean and median diameter and other particle characteristics. 

Apparatus

References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used.

• Beaker, polypropylene, 30-ml

• Bottle, wash, polyethylene, 1000-mL

• Ultrasonic Probe, Branson, Model S-250D

• Particle size analyzer

• Spatula, double blade, flat end

• Stir plate

• Stir bar

Procedure

The analyst is expected to be familiar with general laboratory practices and the equipment being used. This Procedure section gives specific instructions for the analyzer listed in Apparatus. If a differernt analyzer is used, use these instructions as a guide, along with the instructions from the instrument manufacturer, to perform the analysis. 

1. Install the analyzer according to the manufacturer’s instructions. Complete the initial operating check and startup procedure as described in the Instrument Operating Manual to verify instrument operation. Once this is completed, it need not be done again unless service is required. The analyzer software is entirely automated.

2. Standard analysis methods can be developed for each material type that will reduce the set up and analysis time. Enter the parameters listed in Table 1 for the typical “UOP Standard Analysis.” Enter other parameters in different analytical method files as needed for the sample types to be analyzed. See the Instrument Operating Manual for instructions on how to set up

and store multiple analysis methods. 

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