modulator

in comprehensive chromatography
https://doi.org/10.1351/goldbook.09958

Interface device between the two columns in a system for comprehensive two-dimensional chromatography that accumulates or samples narrow bands from the effluent of the first column for fast re-injection into the second column.

Source:
PAC, 2017, 90, 181. 'Terminology of separation methods (IUPAC Recommendations 2017)' on page 209 (https://doi.org/10.1515/pac-2017-0111)