When to use a Light Scattering in High Temperature GPC for Polyolefins
- April, 16 2026
- Category: Intrinsic Viscosity Analysis, GPC/SEC
A Light Scattering detector is as powerful as it is challenging to use for high-temperature applications, such as GPC/SEC. It is the only detector that can provide absolute molar mass results and Long Chain Branching calculations without depending on columns or calibrations. However, its fragility and difficulties for routine analysis are a significant drawback to consider when elaborating your business case and deciding the best configuration in terms of desired performance, usage, and cost during a purchase decision.
In that sense, the winner configuration with the best balance result and robustness is a dual detection system that combines a concentration detector (such as an Infrared Detector IR4 or IR6, or a differential Refractive Index Detector), with a Viscometer detector. This combination allows the calculation of the Long Chain Branching without the inherent inconveniences of using a Light Scattering Detector. This is possible by comparing the Mark-Houwink graphs of the sample to be analyzed against those of linear reference samples, based on measured intrinsic viscosity and molar mass determined by universal calibration. Polymer Char’s One Software allows the LCB analysis in this configuration with the viscosity contraction factor g’, branching number, and branching frequency distributions and averages.
The dual-detector configuration is the most widely used among HT GPC users due to its reliable performance in most of the samples, plus its strong balance between potential technical issues, price and practicality. As a result, it is often preferred over triple-detector configurations, which are significantly more complex, costly and difficult to afford for routine analysis.
When a Triple Detection Configuration is Recommended
When assessing the decision of including a light scattering detector in the HT GPC configuration, this should be considered alongside a thorough review of the types of samples to be characterized. For cases in which the Long Chain Branching content is extremely low, the dual detection configuration might show limitations, and a triple detection configuration is recommended instead.
A triple detection configuration (concentration detector, viscometer and light scattering detector) allows obtaining the Mark-Houwink plot based both on measured intrinsic viscosity and also on absolute molar mass, as well as the Conformation plot when a MALS is used. In this case, Polymer Char’s One Software will provide LCB calculations including both contraction factors g (radius of gyration) and g’ (viscosity), branching number, branching frequency distributions and averages as well as the viscosity ratio, molar mass ration and gpcBR coefficient.
Finally, another particular case in which a light scattering detector may play a significant role in the results, is concretely for UHMWPE samples. These specific samples will challenge the GPC technique separation power itself, and having a MALS detector will help overcome those difficulties with the relative column calibrations in the very high molar mass range (beyond the columns separation range) thanks to its capability of measuring the absolute molar mass.