If we want to know physical or chemical properties of materials we can employ a variety of analytical methods but no matter how refined, organised or well thought out the analytical technique is, if the sample is not a representative sample of the bulk we will learn nothing of value or even worse, base our judgement on wrong data. It is important to understand that particles will naturally segregate, and that segregation becomes worse when materials are moved, handled or transported. A robust sampling methodology is therefore an essential part of any particle analysis regime.
While most industrial processes work with large scale bulk materials, most testing techniques will test only a small quantity of material, with weights in grams or milligrams. This small quantity should posses the same statistical characteristics as the bulk of the material. Properly conducted Representative Sampling, a type of statistical sampling, will allow us to achieve the goal of small samples closely representing the characteristics of the larger quantities.
For example, if a sample is 6kg, only a small portion of the 6kg will be used for the chosen analytical method. To make the sample representative, the sample needs to be sub-divided into separate aliquots until obtaining the quantity required for the analyser. This process of sub-division needs to be conducted in a certain way to guarantee success. The most accurate sample subdivisions are achieved by using rotary rifflers or spinning rifflers.
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