When high polymers are analyzed by SEC, peak tops tend to elute later when the concentration is high. This is called concentration dependency, and caused partly because molecular chains will be easily cut at a high concentration. This figure shows the absolute molar mass by GPC/MALS in different concentrations of standard polystyrene (Mw: 3,800,000). In this analysis, 2 pieces of organic SEC (GPC) KF-806L (particle size: 9 µm) were used, and the flow rate was 1.0 mL/min. As a result, almost the same molecular weights were calculated between 0.02 % and 0.4 %, which means molecular chains are not cut in these concentrations. The chromatogram indicates the signals by RI. The plots of x and + are the molar mass and elution volumes by MALS detection.


Sample : Polystyrene (MW: 3,800,000), 200 μL

Result :
Conc.      Av.Mw (g/mol)
0.02 %       3.795e+6
0.10 %       3.723e+6
0.30 %       3.732e+6
0.40 %       3.723e+6

Columns   : Shodex GPC KF-806L (8.0 mm I.D. x 300 mm) x 2
Eluent    : THF
Flow rate : 1.0 mL/min
Detector  : MALS + RI