Working Within Allowable Changes to the U.S. Pharmacopoeia Naproxen Sodium Tablet Method

Importance of the Topic

Pharmaceutical quality control relies on robust analytical methods to ensure drug safety and efficacy. The official USP assay and impurity test for naproxen sodium tablets is a critical tool for routine testing of raw materials and finished products. However, conventional HPLC setups with 5 µm fully porous columns involve long run times and high solvent consumption. Adapting these methods within allowable USP adjustments can enhance laboratory productivity and reduce costs while maintaining compliance.

Objectives and Study Overview

This application note evaluates the use of superficially porous InfinityLab Poroshell 120 EC-C8 columns and fully porous ZORBAX RR Eclipse Plus C8 columns to accelerate the USP naproxen sodium tablet assay within permissible method changes. The aim is to demonstrate significant reductions in analysis time and solvent usage without requiring full revalidation of the method.

Methodology and Instrumentation Used

The method was run on an Agilent 1260 Infinity II LC system configured with a binary pump, multisampler, multicolumn thermostat, and diode array detector controlled by OpenLab CDS. Sample preparation followed the USP tablet assay protocol (0.1 mg/mL in acetonitrile:water:acetic acid 500:490:10). Columns evaluated included:

• ZORBAX RR Eclipse Plus C8, 4.6×150 mm, 5 µm
• InfinityLab Poroshell 120 EC-C8, 4.6×75 mm or 4.6×50 mm, 2.7 µm

Allowed method adjustments followed USP General Chapter 621, applying L/dp and efficiency-based scaling rules for column length, particle size, flow rate, and injection volume.

Key Results and Discussion

• Switching from 150×5 µm to 75×2.7 µm columns at 1.2 mL/min reduced run time by 52% and solvent use by 50%, maintaining resolution and system suitability (tailing factor <1.1, RSD <0.05%).
• At higher flow (1.8 mL/min), throughput increased by 64%, with analysis complete in ~1.0 minute and acceptable column efficiency and pressure.
• Further miniaturization to 50 mm length yielded up to 76% time savings and 66% solvent reduction at 1.8 mL/min.
• Comparative tests with fully porous 3.5 µm C8 columns confirmed superficially porous particles deliver faster separations while meeting USP criteria.

Benefits and Practical Applications of the Method

• Higher sample throughput in QC laboratories without hardware upgrades.
• Reduced operational cost by lowering solvent consumption.
• Compliance with USP compendial requirements without full revalidation.
• Scalable approach for method transfer across CROs and manufacturing sites.

Future Trends and Applications

Looking ahead, further adoption of superficially porous and sub-2 µm particle UHPLC columns is expected to drive even faster compendial assays. Integration with automated workflows and smaller diameter columns may enable microflow HPLC, supporting greener and more efficient pharmaceutical analysis.

Conclusion

Applying USP‐allowed adjustments to column dimensions and flow parameters enables rapid, cost-effective analysis of naproxen sodium tablets while preserving method integrity. Superficially porous Poroshell 120 EC-C8 columns deliver significant throughput gains and solvent savings on existing Agilent 1260 Infinity II systems, facilitating high‐performance compendial testing.

References

• USP Naproxen Sodium Tablet Method, United States Pharmacopeia 42(4) Proposed IRA, Rockville, MD, 2017.
• USP General Chapter 621, USP 37-NF32 First Supplement.