It is the largest particle size that determines the operative requirements of the riffle splitters. In general, it is obvious whether a target material is suitable for riffle splitting or not. Other than that, there are obvious requirements related to the largest particle size (in some less frequent cases also related to the sorting of the material). The sample material must be free-flowing in order to be able to pass through the riffles, driven by gravity. There are a few requirements in order for riffle splitting to be the perfect way to do mass reduction in the lab, by which is meant the most effective way to obtain representative mass reduction in the lab. Following directly this avenue, the present column deals exclusively with the by far most often used method for mass reduction in the lab-riffle splitting. The last column of 2016 1 dealt with some of these systematics in detail from the perspective of a particularly popular tool, the sampling spear, or the sampling thief. The objective of collecting an increment, or several, is in practice always related to only two possible objectives: to perform grab sampling or composite sampling (see previous columns). The choice of which sampling tool dimension to choose is only related to the lot size vs the desired increment size, all of which is strongly related to the grain size characteristics of the lot. Thus a spatula – is a laboratory spoon – is a shovel – is a spade – is a backhoe grabber – is a crane grabber… All these tools are used to select and extricate an increment, or a sample, it is only the scale that varies. It is very advantageous to view all sampling operations, spanning the entire “from lot-to-analysis” pathway, as a scale-invariant theatre in which the sampling operations are identical, in principle as well as in practice. As is shown below, it pays well to follow TOS’ universal application scope all the way to its ultimate stage, that of selecting (sampling for) the analytical aliquot (the analytical mass). Truth be told, for the many operations falling under the term “sample processing” or “sample preparation”, very nearly all contain straight-forward sampling processes-only writ small, but bona fide TOS operations nevertheless. However, if the systematics of TOS shall be in a position to be used to its full power and reach, this division needs careful attention-it is time to enter THE LAB (see also the last column of 2016 1). This is because many are of the opinion that applying the Theory of Sampling (TOS) at all such large(r) scales (primary sampling) is different from the work thought to belong the analytical realm, which indeed takes place at much smaller scales. While this series is presenting the universal principles behind representative sampling of all types of lots and composition, the focus has studiously been kept outside the analytical laboratory. AKHE Consulting, bSampling Consultant-Specialist in Feed, Food and Fuel QA/QC.
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