test portion

Synonym: analytical portion
https://doi.org/10.1351/goldbook.T06284
The amount or volume of the test sample taken for analysis, usually of known weight or volume.
Source:
PAC, 1989, 61, 1657. 'Nomenclature for automated and mechanised analysis (Recommendations 1989)' on page 1660 (https://doi.org/10.1351/pac198961091657)