Improved identification of extractable and leachable substances with the Orbitrap Exploris GC 240 MS

Significance of the Topic

High-resolution accurate-mass (HRAM) gas chromatography–mass spectrometry (GC-MS) is crucial for identifying extractable and leachable (E&L) compounds in pharmaceutical products. These impurities may arise from contact materials during manufacturing or storage and pose potential safety risks. Leveraging HRAM GC-MS enhances selectivity and sensitivity for a diverse range of volatile and semi-volatile analytes that are challenging for liquid chromatography (LC) alone.

Objectives and Study Overview

This study aimed to evaluate the Thermo Scientific Orbitrap Exploris GC 240 MS, combined with Compound Discoverer software, for comprehensive untargeted analysis of E&L substances. Key goals included:

• Assessing detection sensitivity and structural elucidation in both electron impact (EI) and positive chemical ionization (PCI) modes.
• Comparing GC-HRAM performance to LC-HRAM techniques.
• Demonstrating unknown compound discovery and prioritization workflows.

Methodology

Rubber stoppers were extracted with isopropanol and dichloromethane under ISO 10993-12 conditions. A screening standard mixture of known E&L compounds provided retention time and HRAM spectral references. Chromatographic separation used a TRACE 1610 GC with a TG-5SilMS capillary column and splitless injection. The Orbitrap Exploris GC 240 MS acquired full-scan data at 120,000 FWHM resolving power (m/z 200) with sub-ppm mass accuracy. EI and PCI (methane reagent gas) modes were run sequentially, enabled by NeverVent technology for rapid ion-source switching. Data processing and unknown analysis employed Chromeleon 7.3.2 CDS and Compound Discoverer 3.3 SP2, integrating NIST and custom E&L HRAM libraries.

Used Instrumentation

• Thermo Scientific TRACE 1610 GC with TG-5SilMS (30 m × 0.25 mm × 0.25 µm)
• Thermo Scientific TriPlus RSH SMART autosampler
• Orbitrap Exploris GC 240 MS with ExtractaBrite ion source
• Chromeleon 7.3.2 Chromatography Data System
• Compound Discoverer 3.3 SP2 software

Main Results and Discussion

• GC-HRAM exhibited up to 127-fold greater sensitivity for certain E&L compounds (e.g., di-tert-butyl methylphenol) compared to LC-HRAM.
• Dual-sequence comparison in Chromeleon facilitated direct overlay of GC and LC data sets for compound verification.
• Spectral deconvolution in Compound Discoverer identified 695 unknowns out of 929 detected features after blank subtraction.
• High resolution and mass accuracy enabled discrimination of coeluting species and confident elemental composition assignment (e.g., 3,5-di-tert-butyl-4-hydroxybenzaldehyde at Δ0.03 ppm).
• PCI mode provided clear [M+H]+ and adduct ions for molecular weight confirmation without venting the instrument.

Contributions and Practical Applications

• Enhanced E&L coverage by combining GC and LC platforms for diverse physicochemical profiles.
• Streamlined unknown identification using dedicated HRAM spectral libraries and automated deconvolution workflows.
• Rapid molecular ion confirmation via NeverVent switching to PCI mode, accelerating structure elucidation.
• Improved confidence in safety assessment workflows by detecting low-abundance leachables in complex matrices.

Future Trends and Potential Applications

Advances may include expanding HRAM spectral libraries with emerging polymer additives, integrating machine-learning algorithms for automated identification scoring, and coupling ion-mobility separations for additional selectivity. Continuous development of software workflows will further streamline E&L risk assessment in pharmaceutical quality control.

Conclusion

The Orbitrap Exploris GC 240 MS, in combination with Compound Discoverer software, provides unmatched sensitivity, selectivity, and confidence for untargeted E&L analysis. Its HRAM capability and seamless EI/PCI switching enhance detection of challenging analytes, supporting robust safety evaluations in pharmaceutical development.

References

• ISO 10993-12:2021. Biological evaluation of medical devices — Part 12: Sample preparation and reference materials.
• Pinedo-Gonzalez P, Liu C, Hower D, Lu D, Hackbusch H, Lamb A, Bardsley J. Multi-detector platform for comprehensive identification and quantitation of extractables and leachables. Thermo Scientific Application Note 001401, 2022.