Introduction

LIGHT-SCATTERING measurements are capable of providing particle-size analysis on a broad range of particle sizes in a rapid, convenient fashion. Current technology is capable of measuring from several tens of nanometers to several millimeters in less than one minute. The instruments have proven themselves capable of solving a variety of problems associated with the production and handling of these powders.

Previous versions of these instruments had much more limited size range capabilities (Ref 1). The advent of modern microprocessors has led to the development of more advanced hardware and software designs. These advances have led to many new features that can be beneficial to the user of the equipment. Table 1 lists some of the more important benefits. The positive benefits have led to increasing use of this technique.

Table 1 General features of light-scattering particle-size analysis

Feature

Possible range of features

User benefit

Expanded range

0.02-2000 |,;m

More types of samples can be analyzed

Automatic analysis

Autosampler for 24 samples

Unattended operation of the instrument

Dry analysis

Samples can be run wet or dry

Samples can be run as they are normally used

PC control of the instrument

All standard programs, such as Windows, can be used

Easy storage, retrieval, and analysis of data

Flexible analysis of data

Narrow modes, multimodes, or broad distributions can be analyzed

Broader range of samples can be analyzed quickly

Mie scattering equations can be used

More complicated algorithms are used to analyze data

More correct particle size data are presented

Light-scattering instruments are now capable of determining subtle differences in distributions that are not reflected in a change of the median size of the distribution (Ref 2). In many cases these subtle changes can be correlated to a change in the performance of the particles of interest. This is an important characteristic of the generated data. As correlations are understood and are related back to the processing conditions in the plant, knowledge is gained about process variations. This knowledge can be used in process control and is one reason for the continuing use of the technique.

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