sampling unit

https://doi.org/10.1351/goldbook.10059
Defined quantity of material having a boundary which may be physical or temporal.
Notes:
  1. Examples of physical boundaries are capsules, containers, and bottles.
  2. A number of sampling units may be gathered together, for example in a package or box.
Source:
PAC, 2016, 88, 407. 'Vocabulary of concepts and terms in chemometrics (IUPAC Recommendations 2016)' on page 412 (https://doi.org/10.1515/pac-2015-0605)