Thermal Gradient Interaction Chromatography
For measuring Composition Distribution in Elastomers and Low Crystallinity Polyolefin Copolymers


TGIC Overview


High-Temperature, High-Performance Liquid Chromatography (HPLC) has become recently available for the analysis of polyolefins, a field that is better known under the name of Interaction Chromatography. It was first used in Solvent Gradient Interaction Chromatography mode (SGIC) and it is today extended with the use of a thermal gradient instead, also known as Thermal Gradient Interaction Chromatography (TGIC).

The TGIC technique using carbon-based adsorbents was developed by The Dow Chemical Company to characterize the composition distribution in polyethylene copolymers. This technique requires a cooling (adsorption) and a heating (desorption) step. Elution of the sample takes place in that last heating step, observing a linear dependence of comonomer content to desorption temperatures in a similar manner to TREF and Crystallization Elution Chromatography (CEF), and being molar mass-independent above 20,000 Da.

TGIC will adsorb polymer molecules by the level of molecular surface in contact with the surface of the adsorbent, thus it may discriminate polymers by the level of irregularities in the chain, in a similar approach to crystallization techniques. TGIC, however, separates by adsorption and no co-elution is expected.

Resolution in TGIC is lower than in crystallization techniques but it has the possibility to extend the range of polymers to be analyzed towards the amorphous region which is limited by crystallization techniques. Then, the analyses of elastomers and other amorphous polyolefins are the main application of TGIC.

TGIC is performed with a single solvent, typically o-DCB or 1, 2, 4 TCB in a Crystallization Elution Fractionation instrument with the standard autosampler, injection system, and an infrared detector, only requiring to replace the TREF column by a TGIC column.

TGIC is a technique developed and patented by The Dow Chemical Company and licensed to Polymer Char. 

TGIC Features

· Fully-automated operation with no manual solvent handling. Integrated vial solvent filling, sample dissolution, and in-line filtration
· Fast analysis time of around 2-3 hours including sample dissolution
· The dissolution time can be programmed individually for each vial, therefore, thermal degradation is minimized
· A gentle shaking movement inside of the autosampler oven helps in speeding up the dissolution process without the shear stress of the magnetic stirring bars
· Oxygen can be removed from the vial by the automated nitrogen vials-purge system, in order to prevent oxidation of the dissolving polymer molecules
· Analysis of up to 42 samples sequentially, with the possibility of using different methods each one
· Both TGIC and CEF analyses can be performed in the same instrument with dedicated software packages
· Easy incorporation of Polymer Char’s on-line Viscometer for composition molar mass interdependence
· Option of integrating infrared detector IR5 MCT or IR6 for maximum sensitivity in both concentration and composition signals

TGIC Detectors

The following are the detectors available for TGIC:



The IR4 is the standard Detector integrated by default in all the Polymer Char analytical instruments. IR4 is a dual-wavelength infrared detector, which uses the principle of infrared absorption spectroscopy to measure the concentration and composition in polyolefins.



The IR5 is a high sensitivity infrared detector designed for measuring concentration and short-chain branching with superb stability. It incorporates interference filters at five different wavelengths and a thermoelectrically cooled MCT detector with high sensitivity (no liquid Nitrogen required).



The IR6 Detector is the latest IR Detector developed by Polymer Char, with the same performance and sensitivity than IR5 Detector and the additional capability of measuring carbonyls group in the band of 1740 cm-1. We recommend the IR6 Detectors for users willing to analyze polyolefin type EVA, EBA, and others with carbonyls group present in the IR band above.



A high sensitivity capillary viscometer is an ideal complement to the Infrared detector in some polyolefin characterization instruments such as GPC-IR, TREF, CEF or CRYSTEX.
Viscometer configuration is optimized to achieve a better performance in each technique.

TGIC Software

The TGIC Software is specifically designed for controlling and automating the process; no manpower is required. The software deals with the whole process, including samples preparation with the vials filling and dissolution.

Up to 42 samples can be managed by the software to be run with no supervision. As each sample from the run-queue is injected and eluted, results can be accessed from the calculations database to be reviewed, overlaid with others, to generate a report, export to Excel even when the instrument is still running.




A wide range of the TGIC analytical process conditions are available to the user, to allow the flexibility needed for both routine analysis and research jobs.

Manual mode in the software is also incorporated as in the rest of Polymer Char’s instruments, so the autosampler, dispenser, ovens, pump, etc.; can be directly operated by the user by means of a powerful Virtual Instrumentation interface.





TGIC (Thermal Gradient Interaction Chromatography) technique using carbon based adsorbents was developed by The DOW Chemical Company to characterize composition distribution in polyethylene copolymers.
Polymer Char, the only licensee by The Dow Chemical Company to market this instrument, automates this technique by using simple and reliable hardware and an especially designed control software.

Yes, that is possible because TGIC technique is carried out in a CEF instrument that can perform CEF and TREF techniques.

Up to 42 vials can be handled by the instrument autosampler, and they can be dissolved and analyzed with no supervision required. Each sample can be analyzed with different conditions, so the total time will depend on the analysis method selected for each sample.

The standard amount used in TGIC analysis is 32mg per sample in 8 mL, therefore the instrument can be used both for research and also for quality control.

1,2,4-Trichlorobenzene (TCB) and Orto-Dichlorobenzene (oDCB) are the most commonly used solvents. To use other solvents please consult Polymer Char first.

No sample preparation is required by the user other than weighing the dry samples and putting them inside of the disposable glass vials. The rest of the steps are performed by the instrument automatically: vials filling, dissolution, filtration, injection, elution, etc.

Yes; different analysis conditions can be selected from the software for each vial within the same run, therefore, different samples can be analyzed unattended and with the appropriate dissolution time, crystallization ramp, elution ramp, pump flow, etc.

Solvents don't need to be handled at any time; the whole process is fully automated, the instrument is in charge of all the needed steps: vials filling, dissolution, filtration, injection, elution, etc.

No prefiltration step is required thanks to an in-line filter, which is integrated in the instrument as an option, connected before the TGIC column. Additionally, after each injection, this filter is automatically rinsed with a backflush to become ready and clean again for the next injection.

The instrument incorporates an infrared detector to measure the concentration of the solution that is being eluted and going out of the column. This detector can be Polymer Char's IR4, IR5 or the latest IR6, all in their integrated versions.

A capillary viscometer detector can be connected to the instrument, to obtain information on composition-molar mass interdependence.

After each injection, data can immediately be accessed and calculated through the software database. Polymer Char TGIC Calculations software integrates all detectors' signals in the same package. A reporting tool is available to generate reports in Excel adapted to each user's needs.

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