Shodex Catalogue 2013-2015.pdf - Analytics Shop

Precautions for Polar Polymer AnalysisSize exclusion chromatography analysis of polar polymers can be influenced by unexpected interactions in the column.These interactions may change elution patterns and results in an invalid molecular weight calculation.It is important to reduce them in order to obtain the accurate molecular weight distribution.Interfering interactions likely to be observedStandard AnalysisColumnsInteractions between the analyte and the packing materialsHydrophobic interactionThe analyte is adsorbed into the packing material.This delays the analyte elution, and thus results inunderestimation of its molecular weight (Figure B, D).Ionic interaction(1) Ion ExclusionThe analyte is repelled from the packing material.This accelerates the analyte elution, and thus resultsin overestimation of its molecular weight (Figure A, C).(2) Ion ExchangeThe analyte is adsorbed onto the packing material.This delays the analyte elution, and thus results inunderestimation of its molecular weight (Figure B, D).Interaction within and between the analyteIonic repulsion effects observed within the multivalentmacromolecules causes structure expansionThis accelerates the analyte elution, and thus results inover estimation of its molecular weight (Figure A).Association between the moleculesAssociated molecule detected as a larger molecule(Figure A).Exclusion limitmolecular weightlog MWElution will beacceleratedExclusionlimit volume(C)(A)Elution will beretarded(B)Permeationlimit volume(D)Precautions for Polar Polymer AnalysisInteractions between the analyte and the solventThe multivalent ion of the solvent works as a bridge tobind ionic molecules (analyte).Methods to reduce interactionsAqueous SEC (GFC)Organic solvent SEC (GPC)Ionic InteractionAdd saltHydrophobic interactionIncrease dissociation of the analyteCationic polymer Lower the pHAnionic polymer Higher the pHLower the eluent polarity(Example) Add acetonitrile or methanolIonic InteractionAdd salt(Example) Add LiBr to DMFAdd CF 3 COONa to HFIPHydrophobic interactionLower the polarity of the eluent(Example) Change the eluent from DMF to THFHydrophillic interactionIncrease the polarity of the eluent(Example) Change the eluent from THF to DMF27