Chromatography
Gel permeation chromatography (GPC) is an analytical technique used to separate molecules based on size.
Gel permeation chromatography (GPC), also known as size exclusion chromatography (SEC), is used to measure the molecular weight distribution of polymer samples. Both absolute and relative molecular weight measurements can be obtained. Absolute molecular weight measurements are performed using multi-angle light scattering (MALS) combined with refractive index (RI) measurement.
Relative molecular weight measurements are performed by comparing the refractive index response of a sample to a calibration curve constructed from a range of molecular weight polymeric standards.
Approaches
There are many analytical uses for GPC Analysis. Some of the most common ways we use GPC/SEC to meet our clients’ needs include:
- The analysis of polymer materials to determine molecular weight distributions
- Measurement of absolute molecular weights using light scattering
- Relative molecular weight measurements using refractive index or UV/vis absorbance detector
- Molecular weight analysis of polymers in organic solvents
- Analysis of water-soluble polymers in aqueous mobile phases
Instrument and Sample Considerations
Wyatt Technology TREOS and HELEOS II multi-angle light scattering (MALS) detectors for measurement of absolute molecular weight
Wyatt Technology Optilab T-rEX refractive index detectors for online measurement of polymer concentration and offline dn/dc measurements
Tosoh EcoSEC HT High Temperature GPC system for analysis of polyolefins
We can provide GPC analysis using virtually any solvent system, including hexafluoroisopropanol (HFIP), which is the preferred GPC solvent for polyamides, polyesters, and nylons. As stated by Jason Todd, one of our Chromatography Experts, “The use of HFIP as a GPC solvent allows us to provide high quality molecular weight data on commercially important polymers. HFIP is advantageous because it allows the GPC analysis to be performed at room temperature. Other solvents for these plastic materials typically require high temperatures for solubility. Higher temperatures increase the risk of sample degradation during analysis. HFIP also provides higher quality GPC results compared to the high temperature solvents.”
Samples submitted for GPC/SEC testing must be soluble in an organic solvent or in water. The minimum sample size for GPC Analysis is 20 mg.
Contact us to talk through your specific sample considerations and analysis needs.
Experience
Examples of our experience with SEC Analysis/GPC Analysis include:
- Size Exclusion Chromatography in Hexafluoroisopropanol for engineering polymers (GPC in HFIP)
- Determining the change in molecular weight due to processing conditions, sterilization conditions, or after synthesis
- Failure Analysis Testing
- Analysis of implantable medical devices
- Analysis of packaging materials, to include medical packaging materials