Lemongrass Oil on Rtx-Wax

Importance of the Topic

Lemongrass oil is widely used in food, fragrance and pharmaceutical industries for its characteristic aroma and bioactive properties. Reliable profiling of its volatile components ensures consistent quality, authenticity verification and compliance with regulatory standards. Gas chromatography on polar stationary phases like Rtx-Wax offers high resolution for oxygenated terpenes and related compounds, making it a key method for essential oil analysis.

Objectives and Overview

This study aimed to develop and demonstrate a gas chromatographic method for the separation and identification of major volatile constituents in lemongrass oil. The focus was on achieving baseline separation of monoterpenes, sesquiterpenes and their oxygenated derivatives within a short analysis time using a polar column.

Methodology and Instrumentation

The sample (5 % lemongrass oil in acetone) was injected (1 µL, split 100:1) onto an Rtx-Wax column (30 m × 0.32 mm, 0.25 µm). The inlet temperature was set at 230 °C with a wool-packed liner. The oven program started at 100 °C (0.5 min), ramped to 250 °C at 16 °C/min, then held for 10 min. Hydrogen served as carrier gas (2 mL/min), and nitrogen was used as makeup gas. Detection was performed by FID at 250 °C with constant column plus makeup flow of 52 mL/min. Data were acquired at 50 Hz on an Agilent 7890A GC. Peak identification was confirmed against the NIST MS EI spectra library (2005).

Main Results and Discussion

Thirteen compounds were resolved with retention times ranging from 1.54 min to 5.00 min:

• Camphene (1.543 min)
• D-Limonene (1.806 min)
• β-Ocimene (1.858 min)
• α-Ocimene (1.916 min)
• 4-Nonanone (2.180 min)
• Methyl heptenone (2.212 min)
• Linalool (3.179 min)
• Caryophyllene (3.636 min)
• Z-Citral (4.038 min)
• E-Citral (4.340 min)
• Geranyl acetate (4.490 min)
• α-Amorphene (4.588 min)
• Geraniol (4.997 min)

The Rtx-Wax phase provided clear separation of isomeric compounds such as Z- and E-citral and both ocimene isomers within a 6-minute window. Peak shapes remained sharp and symmetric under the selected conditions.

Benefits and Practical Applications

This rapid GC-FID method enables routine quality control of lemongrass oil batches, detection of adulteration and standardization of aroma profiles. Laboratories can implement it for raw material screening, batch release testing and comparative studies of essential oil chemotypes.

Future Trends and Opportunities

• Two-dimensional GC (GC×GC) with time-of-flight MS for deeper compositional insights
• Hyphenated techniques (GC–MS/MS, GC–Olfactometry) for odor-active compound characterization
• Automated data processing and chemometric approaches for authentication and fingerprinting
• Miniaturized and portable GC systems for in-field oil quality assessment

Conclusion

The described GC-FID method on Rtx-Wax achieves efficient separation and reliable identification of key volatile constituents in lemongrass oil within a short runtime. Its simplicity, reproducibility and sensitivity make it suitable for routine analytical laboratories focused on essential oil quality control.

References

• NIST Mass Spectral Library, Version 2005.
• Restek Corporation. Application Note: Analysis of Lemongrass Oil on Rtx-Wax, 2019.