Advanced SEC-MALS Analysis of Sodium Hyaluronates

Significance of the Topic

Hyaluronic acid and its sodium salts are key biopolymers in pharmaceutical and cosmetic applications due to their viscoelastic and water-retaining properties. Accurate determination of their molar mass and distribution is essential for understanding structure–property relationships and for ensuring consistent product quality in research, development, and quality control environments.

Objectives and Study Overview

This study demonstrates how size-exclusion chromatography (SEC) using Agilent SUPREMA ultrahigh columns, coupled with a Multi-Angle Light Scattering (MALS) detector, enables absolute molar mass determination of ultrahigh molar mass sodium hyaluronates without relying on calibration standards. Key goals include extending the molar mass range beyond that of available polymer standards and improving repeatability of molar mass results.

Methodology and Instrumentation

The analytical setup consisted of the following components:

• Agilent 1260 Infinity III isocratic pump, vial sampler, column thermostat, variable wavelength detector and refractive index detector
• Agilent 1260 Infinity II Multi-Angle Light Scattering Detector (20 angles)
• Three Agilent SUPREMA Linear Ultrahigh columns (8×300 mm, 10 µm) with guard column
• Agilent WinGPC software for data acquisition and processing

Sample and solvent preparation:

• 10 mM phosphate-buffered saline (pH 7.4) as mobile phase
• Sodium hyaluronate solutions at 0.5 g/L, filtered through 1 µm PTFE filters
• Flow rate of 0.5 mL/min, injection volume 100 µL, column temperature 35 °C, run time 120 min

Key Results and Discussion

SEC alone with pullulan calibration fails to cover the elution range of high molar mass hyaluronates, resulting in analyte peaks eluting outside the calibrated region. Coupling with MALS provides:

• Absolute molar mass determination without column calibration curves
• Detection of molar mass and radius of gyration at each elution volume by angular extrapolation to zero degrees
• Clear differentiation between sodium hyaluronate and pullulan standards due to differing coil expansion in solution
• Extension of reliable molar mass assessment into the ultrahigh range (>1×106 g/mol)

Angular dependence plots highlight the necessity of multi-angle data: single-angle analysis can underestimate true molar mass by up to 40%.

Benefits and Practical Applications

The SEC-MALS approach offers:

• Improved repeatability and reduced uncertainty compared to relative calibration methods
• Capability to analyze samples lacking suitable high-molar-mass standards
• Absolute molar mass data for regulatory comparability and quality control

Future Trends and Opportunities

Advances may include higher-throughput SEC-MALS systems, novel column chemistries for even larger molecules, integration with orthogonal detectors (e.g., viscometry), and real-time data analytics powered by machine learning to further streamline macromolecular characterization.

Conclusion

Agilent SUPREMA ultrahigh columns combined with a 1260 Infinity II MALS detector allow reliable, absolute molar mass and size determination of ultrahigh molar mass sodium hyaluronates without conventional calibration standards. This method enhances reproducibility, extends analytical range, and supports consistent quality assessment across laboratories.

References

1. Striegel AM, Yau WW, Kirkland JJ, Bly DD. Modern Size-Exclusion Liquid Chromatography, Chapter 8 Calibration. John Wiley & Sons, 2009.
2. Radke W. Chromatography of Polymers, Macromolecular Engineering, Chapter 13. Wiley-VCH, 2007.
3. Striegel AM, Yau WW, Kirkland JJ, Bly DD. Modern Size-Exclusion Liquid Chromatography, Chapter 9 Physical Detectors. John Wiley & Sons, 2009.