Molecular Weight Determination of Dextran According to USP/EP Monograph

Significance of the Topic

Dextran polymers with defined molecular weights are critical in pharmaceutical applications as they act as plasma volume expanders and influence blood coagulation. Accurate molar mass determination ensures therapeutic efficacy and safety, reducing risks associated with inappropriate molecular weight distributions.

Objectives and Study Overview

This application note describes the implementation of a USP/EP-compliant GPC/SEC method for dextran molecular weight characterization. It outlines the calibration procedure, data acquisition, and analysis workflow using Agilent WinGPC software to meet monograph requirements for dextran 40, 60, and 70.

Methodology and Instrumentation

The study uses aqueous size exclusion chromatography with five dextran standards (4 000–250 000 g/mol), glucose marker (180 g/mol), and determination of column void volume (V0). An iterative nonlinear regression fitting function correlates elution volumes to molar masses. The WinGPC e-workflow guides users through:

• Calibration of dextran standards and glucose sample
• Selection between USP and EP calibration methods
• Automatic fitting validation and report generation
• Evaluation of unknown dextran samples for full, 10%, and 90% eluted mass

Instrumentation Used

• Isocratic pump
• Autosampler with EP/USP specified loading
• SEC columns as described by USP/EP monographs
• Refractive index detector
• Agilent WinGPC software

Main Results and Discussion

• Successful calibration of five dextran standards (4 k to 250 k g/mol), glucose, and V0 using WinGPC overlay and Quick Analysis
• Validation of calibration via the Dextran Monograph Calibration dialog, supporting both USP and EP criteria
• Automated determination of weight-average molar mass (Mw), number-average molar mass (Mn, USP), dispersity (Đ), and fractional masses at 10% and 90% elution
• Generation of compliance reports with pass/fail status based on predefined acceptance limits

Benefits and Practical Applications of the Method

The described e-workflow enables regulated laboratories to perform dextran molecular weight testing efficiently, ensuring compliance with multiple pharmacopeial standards (USP, Pharm. Eur., British, Chinese, Japanese). Features include audit trails, electronic signatures, and customizable reporting for QA/QC and R&D settings.

Future Trends and Opportunities

• Integration of advanced detectors (e.g., multi-angle light scattering) for absolute molecular weight measurements
• Enhanced automation and real-time data analytics to reduce manual intervention
• Extension of the workflow to other biopolymers and complex macromolecules
• Broader acceptance of unified SEC methods across global pharmacopeias

Conclusion

Agilent GPC/SEC systems, combined with WinGPC software, provide a fully integrated solution for dextran molecular weight determination in accordance with USP and EP monographs. The automated calibration, evaluation, and reporting capabilities support regulatory compliance and streamline pharmaceutical testing workflows.

Reference

• Isbister J. P.; Fisher M. Adverse Effects of Plasma Volume Expanders. Anaesth. Intens. Care, 1980, 8, 145.