The discrete identifiable portion suitable for taking as a sample or as a portion of a sample. These units may be different at different stages of sampling.
Source:
PAC, 1988, 60, 1461. 'Nomenclature, symbols, units and their usage in spectrochemical analysis-X. Preparation of materials for analytical atomic spectroscopy and other related techniques (Recommendations 1988)' on page 1463 (https://doi.org/10.1351/pac198860091461)