riffling

in analytical chemistry
https://doi.org/10.1351/goldbook.R05392
The separation of a free-flowing sample into (usually) equal parts by means of a mechanical device composed of diverter chutes.
Source:
PAC, 1990, 62, 1193. 'Nomenclature for sampling in analytical chemistry (Recommendations 1990)' on page 1204 (https://doi.org/10.1351/pac199062061193)