Introduction; Representative Sampling - Malvern Mastersizer Series Getting Started

Introduction

Now that you have successfully made a measurement and analysed the result, we
shall return to the important subject of sample preparation.
The preparation of the sample before it is added to the system can be critical.
Over half the problems encountered when measuring a sample are caused by bad
sample preparation. If your sample is sticking together, dissolving, floating on the
surface or if you have failed to get a representative sample you will not get a
correct result.
There are many techniques available to ensure that the sample is prepared
successfully. Once you have found a suitable dispersion technique for your
sample you can standardise the procedure so that comparisons can be made
between samples.
The information given in this chapter does not assume you are using an
Automated Sample Dispersion Unit - information is given on wet and dry
measurements.

Representative sampling

When taking a sample for a measurement it is most important to ensure that the
sample you are using is representative of the whole sample. If the sample is taken
from a bottle or container then care must be taken to ensure that the sample is
thoroughly mixed. When the sample is a powder large particles tend to rise to the
top of the container, as smaller ones fall to the bottom (as can be seen in the
diagram below).
The large particles in the bottle of powder migrate to the top in transit À.
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G E T T I N G
C H A P T E R 9
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P a g e 9 . 1
S T A R T E D