Abstract: The present invention relates to a computer implemented method (600) performed by a chromatography apparatus (400) configured to separate molecules, having varying size, from an eluent, the method comprising obtaining (610) reference data for a chromatography column of the chromatography apparatus, wherein the reference data is indicative of elution characteristics for a set of molecular sizes, obtaining (620) an elution progress measure and a corresponding quantitative measure indicative of a concentration of molecules in an eluate of the chromatograph) apparatus, estimating (630) a size measure indicative of molecular size of the molecules in the eluate, rendering (640) a representation (300) indicative of the quantitative measure and the size measure, controlling (650) a display to display the representation to a user of the chromatography apparatus.