Analysis of Carboxymethyl Cellulose Using an Integrated HPLC System

Significance of the Topic

Carboxymethyl cellulose is a widely used water-soluble polymer employed in pharmaceuticals, food, and cosmetics. Accurate determination of its molecular weight distribution is essential for quality control and performance evaluation in industrial and research settings.

Objectives and Study Overview

This study explores the measurement of CMC molecular weight distribution using an integrated HPLC system. It compares the performance of sodium nitrate and sodium sulfate as eluents, highlighting their impact on analysis stability and hardware corrosion.

Methodology and Instrumentation

• HPLC System: Shimadzu LC-2050C integrated high performance liquid chromatograph
• Columns: Two Shodex OHpak SB-803 HQ and SB-805 HQ columns in series (300 mm × 8.0 mm I.D.)
• Eluents: 100 mmol/L sodium nitrate and 100 mmol/L sodium sulfate
• Flow Rate: 1.0 mL/min; Column Temperature: 40 °C
• Detection: Refractive index detector (RID-20A) at 40 °C
• Sample: 0.1 % CMC solution; Injection Volume: 50 µL

Main Results and Discussion

Comparison of eluents showed that sodium nitrate provided a higher detector response and effectively suppressed electrostatic interactions without corroding stainless steel components. A calibration curve built with pullulan markers (M.W. 342 to 1 600 000) enabled precise molecular weight estimation. Reproducibility tests (n=6) produced Mn ~78 000, Mw ~263 000, and Mw/Mn ~3.37 with relative standard deviations below 0.7 %.

Benefits and Practical Applications

This approach delivers reliable molecular weight profiles using mild, less corrosive salts, reducing maintenance and extending column life. The integrated HPLC platform also supports non-GFC analyses, improving overall laboratory versatility and throughput.

Future Trends and Potential Applications

Emerging developments may include expanded high molecular weight calibration standards, adoption of metal-free flow paths, enhanced data processing with dedicated GPC software, and real-time monitoring for inline quality control in polymer manufacturing.

Conclusion

The integrated HPLC system coupled with refractive index detection and mild eluent conditions enables stable, reproducible measurement of CMC molecular weight distribution. This versatile setup offers significant advantages for polymer analysis across research and industrial laboratories.