Golden Rules of Sampling

For the many possible situations in which sampling has to be performed, two principles can be given that will decrease segregation  

Rule 1. A powder should be sampled when in motion. 

Rule 2. The whole stream of powder should be taken for many short increments of time in preference to part of the stream being taken for the whole time. 

In many possible situations a sample has to be obtained under conditions that often necessitate the use of inferior sampling techniques, however, observance of these Golden Rules will lead to the best sampling procedure. 

Once a representative sample has been obtained, the particle size distribution and other powder characteristics can be determined. 

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These principles are embodied in The golden rules of sampling... 

With large tonnages, samples taken from conveyors can represent large quantities of material that need to be further reduced. Often, a traversing cutter is used as a primary sampler, and the extracted sample is further cut into a convenient quantity by a secondary sampling device. It must be borne in mind that the secondary sampler must also conform to the golden rules of sampling. This equipment is satisfactory for many applications but it has limitations, which restrict its use. These are ... 

The rotary sample divider or spinning riffler was first described in 1934 [20] and conforms to the golden rules of sampling. The preferred method of using this deviee is to fill a mass flow hopper in such a way that segregation does not occur. The table is then set in motion and the hopper outlet opened so that the powder falls into the collecting boxes. The use of a vibratory feeder is recommended to provide a constant flowrate... 

To satisfy the above requirements, the following basic golden rules of sampling should be followed whenever practicable. 

The principle of the spinning riffler is shown in Fig. 1 and it embodies both golden rules of sampling. The sample is slowly conveyed by a vibratory feeder from the feed hopper onto a... 

USP 429) stress the importance of sampling and advise that a representative sample be prepared using a sample splitting technique. The golden rules of sampling suggested by Allen 1990 are ... 

One must follow the two Golden rules of sampling as proposed by Allen (1981) ... 

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