Characterization of Xanthan

Importance of the topic

Xanthan gum is a high molecular weight heteropolysaccharide extensively used as a thickening agent and stabilizer in food, cosmetics, paints and oil recovery. Accurate characterization of its molecular weight distribution is critical for ensuring consistent performance in formulations and meeting quality control requirements.

Objectives and overview of the study

This application note describes a size-exclusion chromatography method for determining the molar mass distribution of xanthan polymers. It aims to present optimized chromatographic conditions, sample preparation guidelines and instrument settings to achieve reliable and reproducible results.

Methodology and instrumentation

The separation was performed on PSS SUPREMA columns using an aqueous mobile phase of water with 0.07 M disodium hydrogen phosphate. Key parameters include:

• Flow rate: 0.33 mL/min
• Column temperature: 25 °C
• Detection: Refractive index detector (Shodex RI71)
• Calibration: Pullulan standards kit
• Data processing: PSS WinGPC software

Recommended sample concentrations were adjusted by molecular weight range and polydispersity index to maintain narrow peaks and adequate detector response. Injection volume was set to 100 µL.

Main results and discussion

Chromatograms obtained on the SUPREMA columns demonstrated clear separation across a wide molar mass range. Calibration curves based on pullulan standards provided a reliable relationship between elution time and molar mass. The method supports:

• Low molecular weight range (100–10 000 Da)
• Medium range (10 000–1 000 000 Da)
• High range (>1 000 000 Da)

Column sets and individual linear columns were recommended for each range to optimize resolution. The results confirm that column choice, sample concentration and standardized calibration are critical factors for reliable distribution profiles.

Benefits and practical applications of the method

The described SEC method enables quality control laboratories to:

• Monitor batch-to-batch consistency of xanthan gums
• Optimize formulation viscosities in food and cosmetic products
• Assess polymer stability and degradation during processing

Reproducible molar mass data support regulatory compliance and product performance validation.

Future trends and opportunities

Advances in multi-detection SEC (e.g. coupling light scattering or viscometric detectors) will enhance molecular characterization by providing absolute molar mass and branching information. Automated on-line sample preparation and integration with advanced data analytics are expected to improve throughput and data quality. Emerging ultra-high-performance SEC columns may further reduce analysis time while maintaining resolution.

Conclusion

This application note establishes a robust SEC protocol for xanthan gum characterization. By selecting appropriate columns, calibrating with pullulan standards and following concentration guidelines, analysts can obtain accurate molar mass distributions that support product development and quality assurance.

References

• PSS Polymer Standards Service. Column Application Note #10011: Characterization of Xanthan. July 1, 2023.