Characterization of Dextran Sulfate

Importance of the Topic

Dextran sulfate (DS) is a highly sulfated polysaccharide similar to heparin, widely used in biochemical separations and as an anticoagulant substitute. Accurate characterization of its molar mass distribution is essential for quality control, reproducible biological activity and consistent performance in protein fractionation, nucleic acid enrichment and two‐phase separation systems.

Objectives and Study Overview

This application note outlines a robust size‐exclusion chromatography (SEC) method for the characterization of DS. The primary goals are to establish a reliable calibration, define optimal sample preparation conditions, and demonstrate the method’s effectiveness in determining molar mass averages and polydispersity.

Methodology

Chromatographic separation was performed in aqueous SEC mode. Key parameters include:

• Mobile phase: water with 0.1 M sodium nitrate
• Column set: PSS SUPREMA columns selected according to target molar mass range
• Flow rate: 1.00 mL/min
• Temperature: 35 °C
• Detection: refractive index (Shodex‐RI71)
• Calibration: pullulan standards covering the desired molar mass range

Sample concentration guidelines were established to ensure narrow peak shapes and optimal signal‐to‐noise ratios:

• Narrow polydispersity (PDI ≤ 1.5):
   • 100 Da–10 000 Da: 2 g/L
   • 10 000 Da–1 000 000 Da: 1–2 g/L
   • > 1 000 000 Da: 0.5 g/L or lower
• Broad polydispersity (PDI > 1.5): all molar masses at 3–5 g/L
• Injection volume: 100 µL

Chromatographic separation examples and molar mass distribution profiles demonstrated the method’s ability to resolve DS fractions across a broad molecular weight range.

Used Instrumentation

The following hardware and software components were employed:

• Chromatography system equipped with PSS SUPREMA columns
• Refractive index detector: Shodex‐RI71
• Calibration kit: pullulan standards from PSS
• Data analysis: PSS WinGPC software

Main Results and Discussion

The SEC method provided clear elugrams with baseline resolution of DS fractions. Calibration with pullulan standards yielded a reliable correlation between elution volume and log(molar mass). Calculated number‐average (Mn) and weight‐average (Mw) molar masses, as well as PDI values, were consistent across replicate injections. The method’s reproducibility supports its use for routine QC of DS products.

Benefits and Practical Applications

This SEC approach offers:

• High reproducibility and accuracy for DS molar mass determination
• Simple sample preparation and injection protocols
• Flexibility to analyze a wide molar mass range by selecting appropriate column sets
• Compatibility with existing aqueous SEC workflows in pharmaceutical and biochemical labs

Future Trends and Possibilities

Continued advancements are expected in detector sensitivity (e.g., multi‐angle light scattering), integration of microfluidic SEC platforms, and coupling SEC to mass spectrometry for structural analysis. Improved software algorithms will facilitate automated peak deconvolution and more detailed polymer characterization.

Conclusion

The described SEC method using PSS SUPREMA columns and pullulan calibration provides a robust, reproducible, and versatile tool for the characterization of dextran sulfate. Its clear protocols and validated performance make it suitable for quality assurance in research and industrial environments.

References

1. Application Note #10090, Polymer Standards Service, July 2023. 2. Pullulan Calibration Kit Documentation, PSS.