sample pre-treatment 

Synonym: sample preparation
https://doi.org/10.1351/goldbook.08042
Collective noun for all procedures used for conditioning a sample to a defined state which allows subsequent chemical analysis or long-term storage (see material stability).
Note:
Sample pre-treatment includes, for example, mixing, splitting, drying, crushing, stabilization, dissolving, extracting, diluting, precipitating, and derivatizing.
Source:
PAC, 2021, 93, 997. 'Metrological and quality concepts in analytical chemistry (IUPAC Recommendations 2021)' on page 1016 (https://doi.org/10.1515/pac-2019-0819)