Transfer the EP/USP Method for Atorvastatin from a Traditional 5-μm Column to an Agilent Poroshell 120 Column

Importance of Topic

The accurate analysis of organic impurities in atorvastatin calcium is essential to ensure pharmaceutical safety, meet regulatory standards, and maintain product efficacy. Transferring existing EP/USP methods to modern, high-efficiency columns delivers faster results and reduces solvent consumption, supporting both quality control and green chemistry initiatives.

Study Objectives and Overview

This application note describes the transfer of the European Pharmacopeia (EP) and United States Pharmacopeia (USP) method for atorvastatin calcium impurity profiling from a conventional 5 µm column to Agilent’s Poroshell 120 superficially porous 2.7 µm columns. Performance was assessed according to USP Chapter 621 system suitability criteria, comparing runtime, resolution, and solvent use.

Materials and Methods

• Reagents and solvents (HPLC or analytical grade): acetonitrile, stabilizer-free tetrahydrofuran, ammonium acetate, glacial acetic acid, water.
• Columns evaluated:
  
  • ZORBAX Eclipse XDB-C8, 4.6 × 250 mm, 5 µm
  • ZORBAX SB-C8, 4.6 × 250 mm, 5 µm
  • InfinityLab Poroshell 120 EC-C8, 3.0 × 100 mm, 2.7 µm
  • InfinityLab Poroshell 120 SB-C8, 3.0 × 100 mm, 2.7 µm
• Instrumentation:
  
  1. Agilent 1290 Infinity Binary Pump (G4220A)
  2. Agilent 1290 Infinity Autosampler (G4226A)
  3. Agilent 1290 Infinity Thermostatted Column Compartment (G1316C)
  4. Agilent 1290 Infinity Diode Array Detector (G4212A)
• Chromatographic conditions: gradient of acetonitrile/THF/ammonium acetate buffer (pH 5.0) with ratios 21:12:67 to 61:12:27; flow rates 1.5 mL/min (5 µm) and 0.64 mL/min (2.7 µm); column temperature 35 °C; detection at 244 nm.

Key Results and Discussion

• ZORBAX SB-C8 5 µm achieved Rs=1.69 for atorvastatin and impurity B, exceeding the USP requirement of ≥1.5; XDB-C8 failed to resolve critical peaks.
• Poroshell 120 SB-C8 delivered Rs=1.67 in 40 minutes, representing a 60% reduction in runtime and corresponding solvent consumption compared with 115 minutes on the 5 µm column.
• All evaluated columns met USP criteria: tailing factor ≤1.6 and RSD ≤0.6% for replicate injections.
• Real atorvastatin samples showed no detectable impurities, confirming method suitability on both column formats.

Benefits and Practical Applications

• High-throughput impurity profiling accelerates laboratory workflows.
• Lower solvent usage reduces operational costs and environmental footprint.
• Moderate backpressures enable use on standard HPLC systems.
• Compliance with USP/EP monographs ensures regulatory acceptance.

Future Trends and Opportunities

Advancements in superficially porous particles will continue to enhance chromatographic efficiency. Future work may explore multi-component impurity panels, coupling with mass spectrometry for increased specificity, and development of greener mobile phases to further minimize solvent impact.

Conclusion

The EP/USP atorvastatin calcium impurity method was successfully transferred from a traditional 5 µm column to an Agilent Poroshell 120 SB-C8 column. The new method meets all USP system suitability requirements while providing significant reductions in analysis time and solvent consumption.

Used Instrumentation

• Agilent 1290 Infinity Binary Pump (G4220A)
• Agilent 1290 Infinity Autosampler (G4226A)
• Agilent 1290 Infinity Thermostatted Column Compartment (G1316C)
• Agilent 1290 Infinity Diode Array Detector (G4212A)

References

1. Anne Mack. USP Analysis of Diphenhydramine and Pseudoephedrine Using an Agilent Poroshell 120 EC-CN Column. Agilent Technologies Application Note, 2013.
2. USP-35. Atorvastatin Calcium. United States Pharmacopeial Convention, Rockville, MD, USA, 2013.
3. EP 04/2011:2191. Atorvastatin Calcium Trihydrate. Council of Europe, Strasbourg, France, 2011.