Analysis of Sodium Chondroitin Sulfate by ELSD-LT III

Importance of the Topic

Chondroitin sulfate is a key glycosaminoglycan found in cartilage and cell tissues and is widely used in eye drop formulations for corneal protection and in supplements for joint health. Because sodium chondroitin sulfate (SCS) lacks significant UV absorption, sensitive and robust detection methods are required for its quantification in pharmaceutical products.

Study Objectives and Overview

This study evaluates a high-performance liquid chromatography (HPLC) method with evaporative light scattering detection (ELSD-LT III) for the analysis of SCS in standard solutions and commercial eye drops. A comparison is made with refractive index detection (RID) to highlight the advantages of ELSD in gradient elution applications.

Materials and Methods

The calibration curve was constructed using SCS standard solutions at four concentrations (250, 500, 750 and 1000 mg/L). A non-porous C18 column was employed under a gradient program of water/triethylamine/acetic acid and acetonitrile. Eye drop samples were diluted tenfold and filtered prior to analysis.

Instrumentation

• HPLC System: Nexera lite with Mixer MR 20 µL
• Column for ELSD: Imtakt Presto FF-C18 (150 mm × 4.6 mm I.D., 2 µm)
• Detector: ELSD-LT III (wide function mode, drift tube 100 °C, N₂ at 350 kPa)
• RID Comparison: Shodex OHpak SB-806M HQ (300 mm × 8.0 mm I.D., 13 µm) with RID-20A

Results and Discussion

The ELSD response plotted on double-logarithmic axes yielded an excellent calibration linearity (r² = 0.99996). Repeatability at 250 mg/L showed RSDs of 0.11 % for retention time and 2.08 % for peak area (n = 6). Analysis of diluted eye drops determined an SCS content of 629.4 mg/L. In contrast, RID analysis under isocratic conditions using a size-exclusion column failed to resolve the sample matrix and required larger injection volumes.

Benefits and Practical Applications

• ELSD allows gradient elution for improved separation of complex matrices.
• High sensitivity and broad compound compatibility without UV chromophores.
• Shorter analysis times and robust quantification for quality control in pharmaceutical production.

Future Trends and Opportunities

Advancements may include integration of ELSD with mass spectrometry, miniaturized and automated detection modules, and AI-driven method optimization. Such developments will further streamline the analysis of non-UV absorbing biomolecules in regulatory and research laboratories.

Conclusion

The HPLC method with ELSD-LT III on a non-porous C18 column provides a reliable, sensitive and rapid approach for quantifying sodium chondroitin sulfate in eye drop formulations. It outperforms RID in separation capability and analytical performance under gradient conditions.

References

• Shimadzu Corporation. Application Note No. L567: Analysis of Sodium Chondroitin Sulfate by ELSD-LT III. First Edition, September 2020.