sample

in analytical chemistry
https://doi.org/10.1351/goldbook.S05451
A portion of material selected from a larger quantity of material. The term needs to be qualified, e.g. @B00756@, @R05303@, @P04841@, bulked sample, @T06285@. The term 'sample' implies the existence of a @S05463@, i.e. the results obtained on the portions taken are only estimates of the concentration of a @C01281@ or the quantity of a property present in the parent material. If there is no or negligible @S05463@, the portion removed is a @T06284@, aliquot or specimen. The term 'specimen' is used to denote a portion taken under conditions such that the sampling variability cannot be assessed (usually because the population is changing), and is assumed, for convenience, to be zero. The manner of selection of the sample should be prescribed in a sampling plan.
Sources:
PAC, 1989, 61, 1657. (Nomenclature for automated and mechanised analysis (Recommendations 1989)) on page 1660 [Terms] [Paper]
PAC, 1990, 62, 1193. (Nomenclature for sampling in analytical chemistry (Recommendations 1990)) on page 1200 [Terms] [Paper]