High Temperature GPC (HT-GPC): A Complete Guide


What is High Temperature GPC?

High Temperature Gel Permeation Chromatography (HT-GPC) is a specialized form of GPC/SEC (Size Exclusion Chromatography) designed to analyze polymers that are insoluble at room temperature. By operating at elevated temperatures with high-boiling solvents, HT-GPC enables complete dissolution and accurate characterization of materials like polyolefins and other technical polymers.
Like conventional GPC, HT-GPC separates polymer molecules according to size (hydrodynamic volume) as they pass through porous gel columns, providing insights into molecular weight and molecular weight distribution. These parameters are essential to understand polymer performance, processing behavior, and end-use properties.

Why Use Gel Permeation Chromatography at High Temperatures?

Many polymers cannot be dissolved at room temperature in most common solvents. To achieve complete dissolution, high temperatures (often 140 °C or higher) and specialized solvents such as 1,2,4-Trichlorobenzene (TCB) or 1,2-Dichlorobenzene (o-DCB) are required. Once dissolved, the GPC analysis must also be performed at elevated temperatures so that the polymer remains in solution throughout the separation and detection process.

Specialized high-temperature instrumentation is therefore essential. Without full dissolution and stable thermal control, polymers may precipitate during analysis, making accurate molecular weight characterization impossible.
The most frequent materials analyzed by HT-GPC are polyolefins such as polyethylene (PE), polypropylene (PP), and their copolymers. For polyolefin producers, HT-GPC is a cornerstone technique for ensuring product consistency, optimizing processing, and developing advanced resins.

Key Applications in the Polymer Industry

HT-GPC is used in both R&D and Quality Control environments, with applications such as:

• Polyethylene and polypropylene resin development – tailoring molecular weight distribution and branching to achieve desired properties.
• Recycled polymer analysis – evaluating degradation, chain scission, or blending performance.
• Process optimization – linking molecular data to processing behavior and end-product performance.
• Specialty polymer characterization – analyzing high-molecular-weight elastomers or engineering plastics requiring high-temperature dissolution and analysis conditions.

Common Detectors Used in HT-GPC

Different detectors in High-Temperature GPC provide complementary insights into polymer properties:

• Refractive Index (RI): Measures changes in refractive index between the polymer solution and the solvent. It is a universal detector but has limited sensitivity for polyolefins due to their low refractive index increments (dn/dc) in typical high-temperature solvents.

• Infrared (IR): Particularly suited for polyolefins, IR detects specific absorbance bands associated with comonomer content or short-chain branching. This enables measurement of comonomer incorporation along the molecular weight distribution, in addition to concentration.

• Viscometer: Measures the intrinsic viscosity of each eluting fraction. When combined with molecular weight data, it provides valuable insights into polymer branching, molecular conformation, and chain structure.

• Light Scattering (MALS/LALS): Measures the intensity of scattered light at one or multiple angles to directly determine absolute molecular weight and radius of gyration, without relying on calibration standards.

Components of a High Temperature GPC System

Because HT-GPC must operate at high temperatures and with aggressive solvents, the system requires specialized components:

• Thermally controlled compartments: the entire system must be heated in a precise and uniform way to achieve the required dissolution and analysis temperatures, and to prevent polymer precipitation.

• High-temperature resistant components (valves, seals, tubing, etc.) built to withstand long-term exposure to solvents and heat.

• High-temperature GPC columns packed with thermostable porous gels compatible with high-temperature operation.

• Automated sample preparation module for solvent dispensing, and sample dissolution and injection at high temperatures, ensuring reproducibility and operator safety.

• Robust detectors capable of working at constant high temperatures.

High Temperature GPC vs Ambient GPC systems

High-Temperature GPC and Ambient GPC share the same fundamental principle – separating polymers by molecular size – yet their operating conditions and analytical challenges differ dramatically.

Although it may seem cost-effective to use a single instrument for both applications, the practical differences in columns, solvents, detectors, calibration, and temperature control make this approach inefficient and risky. Frequent switching increases downtime, maintenance needs, and the likelihood of data inconsistency or contamination.

This article explores the key differences between HT and Ambient GPC, and how to choose the right setup for your laboratory.

illustration of a GPC column comparing high temperature vs ambient temperature

 

Typical High Temperature Gel Permeation Chromatography Workflow 

High Temperature GPC follows a well-defined sequence to ensure complete dissolution of polymers and accurate molecular weight characterization. The typical workflow includes:

Calibration with Polymer Standards

  • Before analyzing unknown samples, the system must be calibrated with polymer standards of known molecular weight (e.g., polystyrene standards).
  • Calibration curves allow the elution volume to be related to molecular weight for the polymer under study.
  • For absolute molecular weight determination, calibration can be replaced or complemented by light scattering detection.
1. Sample Preparation and Dissolution
  • The polymer sample is weighed and combined with a high-boiling solvent according to the desired concentration.
  • The mixture is heated, typically at 140–160 °C, for a controlled period to ensure complete dissolution.
  • Automated dissolution units are often used to improve reproducibility, minimize polymer degradation, and enhance operator safety when handling hot solvents.
2. Filtration and Injection
  • Once dissolved, the solution is filtered to remove fillers, gel particles, or undissolved residues that could clog the columns. Some GPC systems automate this step by incorporating an inline filter.
  • A defined volume of the filtered solution is then injected into the HT-GPC system using a high-temperature autosampler.
3. Separation in HT-GPC Columns
  • The solution flows through thermostated gel permeation columns, packed with porous beads that act as the stationary phase.
  • Molecules are separated according to their hydrodynamic volume:
    1. Large molecules elute first because they cannot enter small pores.
    2. Small molecules elute later after accessing more pore volume.
  • Choosing the right column set is essential: different pore sizes and packing materials are optimized for specific polymers and molecular weight ranges.
4. Detection
  • Each eluting fraction passes through the detectors – Refractive Index, Infrared, Light Scattering, Viscometer – depending on the system’s configuration.
  • Combining detectors provides a comprehensive polymer characterization beyond molecular weight alone.
5. Data Analysis
  • Specialized GPC software calculates molecular weight averages (Mn, Mw, Mz), polydispersity, and full molecular weight distribution curves.
  • For polyolefins, Infrared detector data enables the study of chemical composition and short chain branching profiles along the molar mass distribution.

How to choose the Right HT-GPC Solution for Your Lab or Plant

Selecting a High Temperature GPC system is not just about buying an instrument, it’s about ensuring that the solution matches your polymer portfolio, analytical goals, and operational constraints. The following factors are key to making the right choice:

1. Polymer Types

a. Different polymers have different solubility and temperature requirements.

b. Some polymers, such as polyolefins, are susceptible to thermal, shear, and oxidative degradation. A reliable HT-GPC system must prevent degradation to deliver accurate, repeatable results.

c. Molecular architecture: consider if you need to analyze complex properties like branching. A multi-detector setup will be necessary to obtain this information. Enlace a blog detectores GPC
 
2. R&D vs QC Needs

a. Research and Development labs often:

  • Handle large sample sets and comparative studies, automation is therefore a must.
  • Require advanced multi-detector systems to capture detailed data on molecular weight distribution, chemical composition, and branching.
  • Depend on robust software capable of integrating inputs from several detectors and supporting flexible method development.

b. Production and Quality Control labs typically:

  • Prioritize speed, robustness, and ease of use.
  • Rely on fewer detectors and optimized column sets for faster analysis with lower solvent consumption.
  • Benefit from simplified, operator-friendly software that delivers consistent results in a routine environment.
  • Read more about the differences between GPC-IR and GPC-QC.
3. Safety and Reliability

a. HT-GPC requires handling hot solvents at 140ºC or higher. Built-in safety features such as solvent vapor management, leak detection, and automated solvent dispensing and sample dissolution are critical.

b. System durability matters: instrument components must be designed for long-term operation under high temperatures and aggressive solvents.

c. Choosing a specialized HT-GPC system ensures reliability and minimizes downtime.

 

4. Support and Expertise

a. Beyond hardware, access to application support, method development guidance, and service reliability should also be factored into the decision.

b. Since polyolefin analysis is a highly specialized field, partnering with a provider that focuses on polyolefin characterization can reduce risk and accelerate results.

GPC-IR by Polymer Char: Advanced High-Temperature GPC Analysis

Polymer Char’s GPC-IR system is the reference solution for high-temperature GPC of polyolefins. Designed specifically for HT applications, it can combine multiple detectors in one integrated platform:

• Infrared (IR) detection for molecular weight and chemical composition distribution analysis of polyolefins or other polymers with significant C-H or C=O content, and soluble in TCB or o-DCB.
• Viscometry for intrinsic viscosity and branching insights.
• Light scattering (MALS/LALS) for absolute molecular weight analysis.
• Refractive index (RI) for universal detection of non-polyolefin materials.

This combination delivers a complete microstructure characterization – molecular weight distribution, chemical composition, and chain structure – in a single workflow.

 

Other features include:

Full Automation and Operator Safety
  • Every step is automated: solvent dispensing, dissolution, filtration, injection, analysis, and instrument cleaning.
  • The system is completely closed, and no solvent vapours are released into the air.
Sample Care to Minimize Degradation
  • Thermal degradation: instead of dissolving all the samples at the same time, the autosampler controls the dissolution–analysis sequence of each vial. This way, each sample is only kept at high temperature for the exact time needed to dissolve it.
  • Shear degradation: gentle shaking is used instead of magnetic stirring to avoid mechanical damage to the polymer chains.
  • Oxidative degradation: each vial is purged with nitrogen to remove the oxygen and create an inert atmosphere.
Column Care to Extend Lifespan

A dedicated temperature-controlled oven keeps columns at high temperature, even if other compartments are cooled for maintenance.
Integrated in-line filter with automated backflush cleaning removes fillers or gels before they reach the columns.
A guard column provides additional protection and extends the column’s lifespan. Read more on this blog post.

Comprehensive Software
  • GPC One® Calculations Software, developed with leading experts in the polyolefin industry.
  • It integrates all detector signals into the most comprehensive GPC analysis package available.
By combining advanced detection, full automation, robust sample and column care, powerful software, and over three decades of dedicated expertise, Polymer Char’s GPC-IR stands as the most complete and reliable solution for high-temperature GPC of polyolefins.

FAQs about High Temperature GPC

Frequently Asked Questions

The most common and abundant polymers that require high-temperature GPC analysis are Polyolefins (polyethylene (PE), polypropylene (PP), and their copolymers). Other high-molecular-weight engineering and specialty polymers such as PEEK, PPS, fluorinated polymers (PVDF), and some elastomers such as cis-1,4-polyisoprene are also insoluble at room temperature and require HT-GPC analysis.

1,2,4-Trichlorobenzene (TCB) and 1,2-Dichlorobenzene (o-DCB) are the most common solvents for polyolefins. Other polymers may require other high-boiling solvents.

Typical injections require just a few milligrams of polymer. Highly sensitive detectors – such as Infrared – can work with as low as 1 mg of sample and still deliver good results.

Polystyrene standards are commonly used for conventional calibration.

Typically 1–2 hours per sample, including dissolution time. This depends on the column setup, detector configuration, and whether automated sample preparation is used.

With proper care – including filtration, guard columns, and stable temperature control – HT-GPC columns can last thousands of injections.

Because Infrared has significantly more sensitivity than Refractive Index for polyolefin detection, its baseline is more stable and lacks negative peaks, making it easier to set the integration limits for data calculation. Besides, IR can measure comonomer content across the molecular weight distribution.

Ensuring complete dissolution of the polymer, avoiding sample degradation (thermal, shear, oxidative), and protecting columns from fillers or gels are the main analytical challenges. Working with aggressive solvents at high temperatures is also a major challenge from the health and safety perspective. Purpose-built HT systems are designed to address these issues.

Yes. HT-GPC is increasingly applied to recycled polyolefins to assess molecular weight distribution and branching, both of which influence processing stability and final material performance.

Ambient GPC is suitable for polymers soluble in common room-temperature solvents. HT-GPC expands the range to polyolefins and other otherwise insoluble materials, but requires specialized instrumentation, solvents, and safety measures.