LECO Accurate Mass Library

Importance of the Topic

Mass spectral databases are essential tools for compound identification in analytical chemistry. The development of accurate mass libraries leverages high-resolution mass spectrometry to enhance confidence and specificity in identifying known and unknown compounds.

Objectives and Study Overview

The primary goal is to present LECO's Accurate Mass Library (AML) for the Pegasus GC-HRT+ system. This effort combines expert curation and novel algorithms to exploit high-resolution data and improve library search results beyond conventional nominal mass comparisons.

Methodology and Instrumentation

Sample analyses were carried out on the Pegasus GC-HRT+ high-resolution gas chromatograph–time-of-flight mass spectrometer. Spectral acquisition at sub-ppm mass accuracy enables pairing of spectral peaks based on mass confidence intervals. The AML contains approximately 760 compounds, including alkanes, polycyclic aromatic hydrocarbons, essential oils, pesticides, and semivolatile organics. Curation was performed in collaboration with academic experts.

Main Results and Discussion

When applied to a complex sample such as extra virgin olive oil, the AML delivers high similarity scores (up to 1000) reflecting precise mass alignment. The AML Rank metric quantifies match quality by summing weighted scores of matched peak pairs, independent of abundance differences. This contrasts with conventional NIST similarity, which relies on nominal masses and relative abundance patterns. Results demonstrate improved discrimination of coeluting or isobaric species.

Benefits and Practical Applications

The accurate mass library enhances routine GC-MS workflows in environmental, food, and forensic laboratories by:

• Increasing confidence in compound identification
• Reducing false positives in screening applications
• Facilitating non-targeted analysis of complex matrices

Future Trends and Opportunities

Expansion of high-resolution spectral libraries and integration with machine learning will enable rapid, automated identification in large-scale screening. Development of cloud-based databases and inter-laboratory sharing will further accelerate method development and regulatory compliance.

Conclusion

LECO’s Accurate Mass Library for the Pegasus GC-HRT+ represents a significant advance in exploiting high-resolution MS data for robust, routine compound identification. The AML Rank metric provides a complementary approach to traditional similarity scoring, offering greater specificity and reliability.

Reference

LECO Accurate Mass Spectral Library. Part Number 359-011-111. LECO Corporation, 2018.