Gel permeation chromatography is a well-developed technique for determining the molecular weight distribution of polymers. Dr Greg Saunders reports.
Traditionally, gel permeation chromatography (GPC) has been performed on modular liquid chromatography equipment composed of separate pump, injection and detection modules.
Integrated instruments, where all these components are contained within a single system, have been typically high cost systems for use in the analysis of difficult samples, such as polyolefins at high temperature.
This article discusses a new cost-effective integrated GPC instrument, the PL-GPC 50, designed for routine laboratory applications, as shown in Fig. 1. The versatility of the instrument shall be explored and the operation discussed for suitability in analytical laboratories.
Instrument versatility
The PL-GPC 50 integrated system is composed of a pump, an electronically actuated injection valve, a column oven capable of heating to 50°C and a differential refractive index detector, all of which are controlled through a software interface.
The instrument can be expanded by additional modules such as an on-line degasser mounted within the unit or an autosampler situated to the side.
The PL-GPC 50 can also accommodate ultra-violet and viscometer detectors and a static light scattering detector may also be connected to the system, allowing multiple detector analysis. These additional modules are controlled within the PL-GPC 50.
The heating capacity along with the wide array of detector modules and peripherals make the PL-GPC 50 a versatile instrument capable of handling the majority of GPC applications, including multi detector analysis.
Reliability
The PL-GPC 50 with a differential refractive index detector was assessed for reliability of operation.
The instrument was set up in the following manner:
* Columns: 2xPLgel 5µm MIXED-C, 300x7.5mm.
* Eluent: THF (stabilised).
* Flow Rate: 1.0ml/min.
* Inj Vol: 100µl.
The PL-GPC 50 then was used to analyse five separate injections of a broad polystyrene, as shown in Fig. 2. Again, the high level reproducibility obtained for the analysis is illustrated by the quality of the overlay.
Conclusions
The variety of module options available illustrates the versatile nature of the PL-GPC 50 as a very cost-effective instrument for gel permeation chromatography.
With integral control software and the capability to do triple detection, the PL-GPC 50 can accommodate most commercial gel permeation chromatography.
Results of the analysis of broad polystyrene demonstrate the suitability of the instrument for applications that rely upon robust operation and reproducible results, such as research and development and quality control.
Overall, the PL-GPC 50 from Polymer Laboratories represents a significant advance in integrated instrumentation for gel permeation chromatography.
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Dr Greg Saunders is Manager, Polymer Characterisation Technical Support, Polymer Laboratories Ltd, Church Stretton, Shropshire, UK. www.polymerlabs.com
