Sniff, sniff, take a whiff - Accurate determination of flavours and fragrances

Importance of the Topic

Gas chromatography mass spectrometry is a central technique for analyzing flavours and fragrances but often struggles to distinguish structural isomers due to similar fragmentation patterns. Linear retention indices provide an orthogonal parameter based on retention behavior, improving confidence in compound identification for essential oils and related samples.

Study Objectives and Overview

This work presents the integration of automatic linear retention index calculation into GCMSsolution software, combined with a tailored FFNSC 1.2 library for quantitation and identification of flavour and fragrance compounds. The study aims to enhance library search accuracy and streamline method adaptation after column changes.

Methodology and Instrumentation

The linear retention index is calculated from retention times of n alkane standards under a linear temperature program using the formula LRI = 100 n + 100 (RTT – RTCn) / (RTCn+1 – RTCn). Shimadzu GCMS QP2010 with GCMSsolution software acquires both reference and sample runs. The FFNSC version 1.2 library contains approximately 1200 electron impact mass spectra with corresponding LRIs measured on a quadrupole system. An Auto Adjustment of Retention Times function updates target analyte retention times based on measured LRI, maintaining method parameters after column cutting or replacement.

Main Results and Discussion

Automatic LRI calculation enabled direct linkage of n alkane reference runs to sample data, generating LRIs for all unknown peaks. Implementing an LRI filter in library searches reduced false positive identifications among isomeric terpenes. A case example demonstrates accurate assignment of sabinene by combining mass spectral match with retention index agreement. Retention time lists for quantitative targets are automatically updated via the AART feature, preserving chromatographic performance.

Benefits and Practical Applications

Integrating LRI calculation within the acquisition software streamlines method development and quality control in flavor and fragrance analysis. The combined mass spectral and retention index matching enhances selectivity and reduces manual data review. The AART function simplifies column maintenance workflows by updating retention parameters from a single alkane run.

Future Trends and Applications

Continued expansion of retention index spectral libraries will further improve analytical coverage for natural and synthetic compounds. Integration with two dimensional gas chromatography and machine learning based spectral deconvolution may offer enhanced resolve of complex mixtures. Novel stationary phase technologies could refine retention index reproducibility across platforms.

Conclusion

Automatic linear retention index calculation in GCMSsolution software, combined with the FFNSC 1.2 library, offers a robust approach for reliable identification of flavor and fragrance compounds. The adoption of LRI filters and automatic retention time adjustment streamlines workflows and enhances confidence in isomer differentiation.

References

• Luigi Mondello, Paola Dugo, Annamaria Basile, Giovanni Dugo, Keith D Bartle Interactive Use of Linear Retention Indices on Polar and Apolar Columns with a MS Library for Reliable Identification of Complex Mixtures J Microcol Sep 7 6 581-591 1995
• Robert Shellie, Luigi Mondello, Philip Marriott, Giovanni Dugo Characterisation of lavender essential oils using gas chromatography mass spectrometry with correlation of linear retention indices J Chromatogr A 970 225-234 2002
• Robert Shellie, Giovanni Zappia, Luigi Mondello, Giovanni Dugo, Philip Marriot Interactive use of Linear Retention Indices on Polar and Apolar Columns with a MS Library for Characterisation of Australian Tea Tree Oils J Essent Oil Res 15 305-312 2003