Gel Permeation Chromatography
Gel permeation chromatography (GPC) was discovered in 1964 by J.C. Moore. Moore’s work involved the use of cross-linked polystyrene “gels” for separating synthetic polymers soluble in organic solvents. GPC is normally used as an analytical procedure for separating molecules by their difference in size and to obtain molar mass averages (Mn, Mw, and Mz) or information on the molar mass distribution (MMD) of the polymers. The raw-data GPC curve is a molecular size distribution curve. If a concentration-sensitive detector, such as a refractive index detector (RI) is used, the GPC curve is really a size distribution curve in weight concentration. Conversely, if a calibration curve or static light scattering detection is used, the raw data are converted to a molar mass distribution curve and the respective molar mass averages can be calculated.
A multi-detector GPC experimental set-up composed of a refractive index detector (RI), light scattering detector (MALS), and differential viscometer (VISC) facilitates three independent modes of determining the molar mass averages and molar mass distributions of a sample. RI and VISC determine the molar mass by peak position and universal calibration respectively, while MALS determines absolute molar mass. Each of these methods has its own advantages and disadvantages, and often produces varying results. GPC coupled to various detection methods (RI, MALS, UV, VISC, QELS) also allows for the characterization of a variety of polymer properties such as co polymer composition, intrinsic viscosity, polymeric size (viscometric radius, radius of gyration or root-mean-square radius, or hydrodynamic radius), and confirmation or architecture through Mark-Houwink plots or dimensionless ratios.
EcoSEC GPC Systems
For over 35 years Tosoh scientists have been perfecting GPC instrumentation through the progression of the EcoSEC GPC System (for polymer analysis up to 50 ºC) and the EcoSEC High Temperature GPC System (for polymer analysis up to 220 ºC). The foundation of both EcoSEC GPC Systems is an all-in-one system designed with: a dual flow refractive index detector (RI) for unmatched baseline stability, temperature controlled dual pumps for excellent flow rate precision independent of changes in laboratory temperature, and an all-in-one design controlled by intuitive software.