diluter

https://doi.org/10.1351/goldbook.D01738
A device used to add a measured volume or amount of the sample to a measured volume of a diluent.
Source:
PAC, 1989, 61, 1657. 'Nomenclature for automated and mechanised analysis (Recommendations 1989)' on page 1661 (https://doi.org/10.1351/pac198961091657)