High Speed GPC Analysis by Nexera™ GPC System: Calculation of Molecular Weight and Quantitative Analysis of Additives

Importance of the Topic

The distribution of molecular weight in polymers is a critical parameter for predicting material performance in applications ranging from plastics processing to quality control in manufacturing. Gel permeation chromatography is a standard technique for determining polymer molecular weight averages and distribution. Accelerating this analysis without compromising accuracy addresses industry demands for high throughput and rapid decision making.

Study Objectives and Overview

This study demonstrates a high speed GPC workflow using a small particle size column and a UHPLC based system to reduce cycle time while ensuring reliable molecular weight data. A further aim is to integrate direct detection of low molecular weight additives in a single run by combining a photodiode array detector with deconvolution software, eliminating the need for preparative fractionation and secondary chromatography.

Methodology and Used Instrumentation

A UHPLC system equipped for GPC analysis was employed under the following conditions:

• System Nexera XR GPC
• Column Shodex GPC HK-404L 150 mm x 4.6 mm, 3.5 µm
• Mobile phase Tetrahydrofuran at 0.8 mL per minute
• Temperature Column and detectors held at 40 °C
• Detection Refractive index detector RI-504 and photodiode array SPD-M40 covering 190 to 400 nm
• Sample 0.2 percent polystyrene solution, injection volume 5 µL
• Analysis time Approximately 3.5 minutes per injection

Calibration was performed with nine polystyrene standards spanning molecular weights from about 1,200 to 2.48 million daltons. Repeatability was evaluated over five consecutive injections.

Main Results and Discussion

A linear log molecular weight versus retention time calibration curve was established with high correlation across the full standard range. High speed GPC runs exhibited an elution window of approximately 1.6 to 2.0 mL, enabling a three and a half minute cycle time with stable baselines. Calculated averages for a test polystyrene sample yielded a number average molecular weight of 2.73 x 10⁴ and a weight average molecular weight of 4.67 x 10⁴ with polydispersity of 1.71. Relative standard deviations were under 1 percent for both averages.

Simultaneous detection of the polymer additive standards Irganox 1010 and Tinuvin 144 by the PDA showed overlapping peaks at 254 nm. Applying the i-PDeA II deconvolution algorithm separated these contributions into individual chromatographic traces. Quantitative analysis based on this deconvolution delivered additive contents of 26.9 milligrams per gram and 3.9 milligrams per gram respectively.

Benefits and Practical Applications

This high speed GPC approach reduces analysis time by more than half compared to conventional methods without sacrificing data quality. The integration of spectral deconvolution into routine GPC provides a powerful tool for laboratories needing both polymer characterization and additive quantification in a single rapid analysis.

Future Trends and Possibilities

Advances in column technology and UHPLC instrumentation will widen the accessible molecular weight range at high throughput. Further developments in multivariate deconvolution algorithms may enable the analysis of more complex additive mixtures. Coupling high speed GPC with mass spectrometry or automated sample preparation could yield comprehensive polymer profiling platforms for research and quality control.

Conclusion

The Nexera XR GPC system with a 3.5 µm column demonstrates reliable high speed molecular weight determination and simultaneous low molecular weight additive analysis. The use of PDA spectral data and intelligent peak deconvolution unlocks new efficiency in polymer testing workflows.

References

• Shimadzu Technical Report No. C191-E042