Identification and Characterization of an Isolated Impurity Fraction: Analysis of an Unknown Degradant Found in Quetiapine Fumarate

Significance of the Topic

Impurity profiling in drug development is essential to ensure safety and efficacy of pharmaceutical compounds. Characterizing unknown degradation products guides formulation strategies and regulatory compliance

Objectives and Study Overview

This study focuses on isolating and elucidating an unknown impurity that appears during forced degradation of quetiapine fumarate. The aim was to determine its elemental composition and molecular structure using advanced liquid chromatography and high-resolution mass spectrometry

Methodology and Instrumentation

Ultra performance liquid chromatography was performed on a C18 column at elevated temperature with a rapid acetonitrile gradient under basic aqueous conditions

• System ACQUITY UPLC with BEH C18 column
• Mobile phases ammonium bicarbonate buffer pH 9.0 and acetonitrile
• Flow rate 0.8 mL per minute, column temperature 65 °C

Mass spectrometric analysis employed a SYNAPT Q-Tof system in positive electrospray mode

• Accurate mass acquisition for MS and MS/MS
• Mass range 100–1000 m/z
• Collision energy ramping 15–30 V
• Lock mass correction with leucine enkephalin

Data processing leveraged MassLynx software with MassFragment for automated fragment assignment

Main Results and Discussion

Accurate mass measurement of the impurity (m/z 402.1838) yielded a best‐fit formula C21H28N3O3S after isotopic and elemental filtering. Three structural hypotheses were generated including sulfoxide, nitroso and amino/ketone variants. MS/MS fragmentation patterns supported the amino/ketone structure by matching key product ions at m/z 137.0063, 199.0454, 228.0464, 253.0803 and 309.1260. MassFragment analysis further ruled out alternative structures by identifying chemically plausible bond cleavages only consistent with the amino/ketone candidate. NMR analysis of the isolated fraction confirmed the proposed hydrolytic degradation mechanism

Benefits and Practical Applications

The combined use of high‐resolution Q‐Tof data and intelligent fragment assignment accelerates impurity identification and increases confidence in structural assignments. This approach supports rapid decision making in formulation development, quality control and regulatory submissions

Future Trends and Opportunities

Integration of machine learning with high‐accuracy mass spectrometry and automated fragmentation tools will further streamline impurity profiling. Emerging hybrid instruments and enhanced software algorithms promise deeper structural insight and reduced analysis time in pharmaceutical research

Conclusion

The study demonstrates a robust workflow for unknown impurity characterization using UPLC Q‐Tof MS and MassFragment software. Accurate mass data combined with targeted MS/MS and NMR validation provided unambiguous structural identification of a quetiapine degradant

Used Instrumentation

• Waters ACQUITY UPLC with BEH C18 column
• Waters SYNAPT Q-Tof MS system
• MassLynx with MassFragment plugin

References

1. Ahuja and Alsante Handbook of Isolation and Characterization of Impurities in Pharmaceutical Compounds Elsevier 2003
2. Jones et al Method Development of an Impurity Profile for Quetiapine Fumarate Waters 2009
3. Jones et al Impurity Isolation and Scale-up from UPLC Methodology Waters 2009