Analysis of Impurities in Atorvastatin Using Single Quadrupole Mass Spectrometer

Significance of the Topic

Pharmaceutical products contain active ingredients and trace impurities such as side products, residual reagents, and degradation molecules. Regulatory guidelines require identification and quantification of impurities above threshold levels for safety assurance.

Objectives and Study Overview

This study demonstrates the application of Shimadzu LCMS-2050 single quadrupole mass spectrometer coupled to Nexera XR HPLC for analysis and identification of impurities in atorvastatin calcium. Key goals include obtaining molecular weight data, overlaying mass signals on UV chromatograms, and using in-source CID for structural elucidation.

Methodology and Instrumentation

• Sample Preparation: 1 mg/mL atorvastatin calcium solution (purity ≥ 98%).
• Liquid Chromatography:
  • System: Nexera XR with Shim-pack XR-ODS column (50 mm × 2.0 mm I.D., 2.2 µm).
  • Mobile Phases: A = 10 mM ammonium acetate aqueous, B = acetonitrile.
  • Gradient: B conc. 10 % (0–2 min) → 30 % (4–6 min) → 100 % (20 min).
  • Flow Rate: 0.3 mL/min; Column Temperature: 40 °C; Injection Volume: 1 µL.
  • Detection: PDA 190–800 nm with direct mass overlay (Mass-it™ function).
• Mass Spectrometry:
  • Ionization: ESI/APCI dual ion source.
  • Scan Mode: SCAN m/z 100–1000.
  • Nebulizing Gas Flow: 2.0 L/min; Drying Gas Flow: 5.0 L/min; Heating Gas Flow: 7.0 L/min.
  • DL Temperature: 200 °C; Desolvation Temperature: 450 °C; Interface Voltage: 3.0 kV.
  • Qarray Voltage: 20/120 V; In-source CID to obtain pseudo-MS/MS spectra for fragment analysis.

Main Results and Discussion

UV chromatograms revealed two impurity peaks (Impurity 1: 0.20 %, Impurity 2: 0.78 %) eluting near the atorvastatin peak at 10.5 min. Total ion chromatograms confirmed these peaks in the LCMS-2050 data. Average mass spectra provided monoisotopic masses of m/z 541.3 and 573.4. In-source CID produced fragment ions at m/z 422.2 and 454.2, respectively. Comparison with theoretical values and predicted fragmentation patterns led to assignment as EP10.4 impurities H and G.

Benefits and Practical Applications of the Method

• Simultaneous UV and mass detection accelerates impurity profiling and confirmation.
• Overlay of mass signals on UV chromatograms simplifies peak identification and reveals low-absorbance components.
• In-source CID provides rapid structural insights without additional MS/MS hardware.

Future Trends and Potential Applications

Emerging high-resolution and ion mobility mass spectrometry will further enhance impurity characterization. Improvements in automated data processing, integration with HRMS workflows, and increased sensitivity are expected to broaden applications in drug development, quality control, and regulatory compliance.

Conclusion

The coupling of Nexera XR HPLC with LCMS-2050 single quadrupole mass spectrometry enables efficient detection, identification, and structural elucidation of pharmaceutical impurities. Mass overlay on UV chromatograms combined with in-source CID supports comprehensive impurity analysis and robust safety assessments.