In analytical chemistry, sub-sampling is a procedure by which a small, representative sample is taken from a larger sample. Good sub-sampling technique becomes important when the large sample is not homogeneous.
Coning and quartering
Coning and quartering is a method used by analytical chemists to reduce the sample size of a powder without creating a systematic bias. The technique involves pouring the sample so that it takes on a conical shape, and then flattening it out into a cake. The cake is then divided into quarters; the two quarters which sit opposite one another are discarded, while the other two are combined and constitute the reduced sample. The same process is continued until an appropriate sample size remains. Analyses are made with respect to the sample left behind.
- "IUPAC Gold Book". Retrieved 2007-11-09.
- "IUPAC Coning and Quartering (in analytical chemistry)". Retrieved 2007-11-09.