Optimizing Aggregate Analysis – Pore Size

Significance of the Topic

Size exclusion chromatography (SEC) is a fundamental analytical technique in biopharmaceutical development and quality control. By separating biomolecules based on their hydrodynamic size, SEC provides critical information on monomeric forms, fragments, and aggregates of therapeutic proteins. Monitoring aggregate levels is essential to ensure product efficacy, safety, and regulatory compliance.

Objectives and Study Overview

This study evaluates the impact of stationary-phase pore size on SEC performance using Shim-pack Bio Diol columns (60 Å, 120 Å, 200 Å, 300 Å) on a Nexera Bio UHPLC system. A standard gel filtration mixture of thyroglobulin aggregates, thyroglobulin, γ-globulin, ovalbumin, myoglobin, and vitamin B12 was analyzed to determine optimal column selection for target molecular weight ranges.

Methodology

Ultrapure water-diluted Bio-Rad gel filtration standards were injected (8 µL) into the UHPLC under isocratic conditions. The mobile phase consisted of 0.1 M sodium phosphate buffer (pH 7) with 0.1 M NaCl at a flow rate of 0.5 mL/min. Columns (300 mm × 4.6 mm, 3 µm) were operated at 25 °C. Retention times and resolution values between adjacent protein peaks were recorded.

Instrumentation

• Nexera Bio UHPLC system (Shimadzu)
• Shim-pack Bio Diol columns: Diol-60 (60 Å), Diol-120 (120 Å), Diol-200 (200 Å), Diol-300 (300 Å)
• UV detector at 280 nm

Key Results and Discussion

Resolution between high-molecular-weight components improved with larger pore sizes. The 60 Å column failed to resolve large proteins, while 120 Å provided partial separation of mid-range proteins. The 200 Å and 300 Å columns achieved baseline resolution for aggregates, thyroglobulin, and γ-globulin. Conversely, resolution of small proteins (ovalbumin, myoglobin, vitamin B12) decreased as pore size increased, as smaller analytes could penetrate larger pores more readily. Repeatability studies on the 300 Å column showed relative standard deviations below 0.3% for retention times and peak areas over six injections, indicating robust performance.

Benefits and Practical Applications

• Guides column selection based on molecular weight targets: Diol-60 for <10 kDa, Diol-120 for 1–100 kDa, Diol-200 for 5–300 kDa, Diol-300 for 20–1,000 kDa.
• Facilitates rapid method development for monoclonal antibodies, oligonucleotides, and carbohydrate conjugates.
• Ensures high resolution and reproducibility for aggregate quantification in biopharmaceutical QC.

Future Trends and Potential Applications

Ongoing advances may include coupling SEC with multi-angle light scattering (MALS) or mass spectrometry for absolute molecular weight determination. Automated column screening and advanced data analysis tools will further streamline method development. Novel stationary phases tailored for ultra-high-throughput and micro-scale SEC formats are emerging for process analytical technology (PAT) applications.

Conclusion

Pore size selection in SEC critically influences the separation of protein aggregates and fragments. Shim-pack Bio Diol columns with varied pore diameters offer flexible options to match analyte size ranges, delivering high resolution and repeatability. This approach simplifies method optimization in biopharmaceutical characterization workflows.

References

No formal references were cited in the original document.