A rapid fenoprofen USP assay method

Importance of Topic

Modernization of pharmacopeial assays is critical to meet current demands for rapid, cost-effective, and environmentally responsible quality control in pharmaceutical analysis. Fenoprofen, an NSAID commonly used in generics manufacture, serves as an ideal candidate to demonstrate how USP <621> guidelines can enable substantial improvements in throughput and solvent usage without compromising method performance.

Goals and Study Overview

The primary objective was to adapt the official USP fenoprofen chromatographic assay to a high-throughput UHPLC format while remaining within—or judiciously extending—the USP <621> modernization criteria. Specific aims included:

• Comparing legacy C18 and modern core-shell C8 columns for equivalence in selectivity and resolution.
• Applying scaled flow rate and column dimension adjustments to reduce run time and solvent consumption.
• Further optimizing temperature and flow to push assay time below USP minimum without losing acceptance criteria.

Methodology and Instrumentation

Sample Preparation:
Primary and working standards of fenoprofen and gemfibrozil were prepared in methanol/water (70:30 v/v) at 1 mg/mL and 0.1 mg/mL, respectively. Vials were labeled via an automated Virtuoso system.

Chromatographic Conditions:
Mobile phase A: Water/0.1% phosphoric acid (92:8 v/v)
Mobile phase B: Acetonitrile
Isocratic elution with on-pump mixing varied per column dimensions.

Použitá instrumentace

• Vanquish Flex Quaternary UHPLC system (SmartInject technology)
• Diode Array Detector with LightPipe flow cell (10 mm path)
• Quaternary Pump F, Split Sampler FT, Column Compartment H, Active Pre-heater
• Accucore C8 columns (150 × 4.6 mm, 100 × 4.6 mm, 100 × 2.1 mm and 50 × 2.1 mm; 2.6 µm core-shell)
• LC-MS grade solvents: water, acetonitrile, formic acid, orthophosphoric acid

Main Results and Discussion

1. Legacy Method Baseline:
150 × 4 mm, 5 µm Hypersil GOLD C8 at 2 mL/min gave a 6 min run time.
2. Core-Shell Equivalence:
150 × 4.6 mm (4 µm) and 100 × 4.6 mm (2.6 µm) Accucore columns achieved similar selectivity (resolution > 2) with run times of 4.5 min.
3. Column Scaling:
Switching to 100 × 2.1 mm at 0.417 mL/min reduced solvent consumption seven-fold without changing elution profile.
4. Flow and Temperature Optimization:
Increasing flow to 0.7 mL/min (within ±50% USP limit) cut run time to 2.5 min. Pushing to 1.0 mL/min and raising temperature to 45 °C yielded a 1.5 min assay with resolution > 20.
5. Repeatability:
24 replicates at optimized conditions showed RSD ≤ 0.2% for retention time and ≤ 1.6% for peak area.

Benefits and Practical Applications

• Four- to five-fold increase in sample throughput.
• Eight- to ten-fold reduction in mobile phase consumption and waste, lowering per-sample costs.
• Maintenance of USP quality criteria (resolution, plate count, repeatability).
• Reduced method complexity with isocratic elution and simple mobile phases.

Future Trends and Opportunities

Continued method modernization may include automated column switching, integration of green solvent alternatives, and expansion to other small-molecule assays. Advances in detector sensitivity and UHPLC hardware could further compress analysis times and enhance lab productivity.

Conclusion

This work demonstrates practical application of USP <621> modernization principles to fenoprofen assay, delivering a robust UHPLC method that dramatically increases throughput, reduces costs, and aligns with current analytical demands without compromising pharmacopeial standards.

Reference

1. Accucore HPLC Columns Technical Guide, Thermo Fisher Scientific