Analysis of Aroma Components in Essential Oils with AOC™-30i

Significance of the Topic

Essential oils contain valuable aroma compounds used in cosmetics, foods and fragrances. Their high viscosity and complex matrices pose challenges for gas chromatography, often requiring dilution that can hinder detection of trace components. Efficient, reproducible direct analysis methods are vital for quality control, research and industrial applications.

Objectives and Study Overview

This study evaluated the performance of Shimadzu Nexis GC-2030 coupled with the AOC-30i autosampler and its Sampler Navigator presets to enable direct injection of undiluted essential oils. Lemon and peppermint oils served as test samples to assess injection stability, reproducibility and prevention of carryover.

Methodology and Instrumentation

The analysis employed the following setup:

• Gas chromatograph: Nexis GC-2030
• Autosampler: AOC-30i with Sampler Navigator, using the “Inject Viscous Sample” preset
• Microsyringe: Xtra Life, 10 µL
• Column: SH-Rtx™-Wax (30 m × 0.32 mm I.D., 1.0 µm)
• Carrier gas: Helium at linear velocity 40 cm/s
• Injector temperature: 260 °C, split ratio 1:100, injection volume 0.5 µL
• Oven program: 90 °C initial, ramp 8 °C/min to 240 °C, hold 15 min
• Detector: FID at 300 °C, H₂ 32 mL/min, Air 200 mL/min, makeup He 24 mL/min
• Wash solvents: prewash acetone; postwash ethanol, acetone, hexane in four 4 mL vials to minimize carryover
• Sampler Navigator settings: middle plunger speed for injection/suction, 3 s viscosity compensation, no extra presolvent wash

Results and Discussion

Under default settings, high-viscosity lemon oil injections showed incomplete sample delivery by the 8th injection. Switching to the “Inject Viscous Sample” preset ensured full sample transfer and stable chromatograms over consecutive runs. Analysis of peppermint oil identified 17 key aroma compounds with area reproducibility below 0.8% RSD (n=5), demonstrating robust performance without dilution. The multi-solvent wash strategy effectively prevented carryover and solvent depletion.

Benefits and Practical Applications

The described approach offers:

• Direct analysis of undiluted essential oils, preserving trace components
• One-click preset application via Sampler Navigator for rapid method setup
• Enhanced reproducibility and reduced carryover through multi-solvent syringe washing
• Reduced sample preparation time and complexity for QA/QC and research

Future Trends and Opportunities

Advancements may include integration of AI-driven injector parameter optimization, expansion to other viscous matrices (e.g., vegetable oils, resins), further miniaturization of autosampler designs, and coupling with mass spectrometry for comprehensive aroma profiling and identification.

Conclusion

The combination of Nexis GC-2030 and AOC-30i with the “Inject Viscous Sample” Sampler Navigator preset enables reliable, reproducible gas chromatographic analysis of undiluted essential oils. This method simplifies workflow, maintains sensitivity for trace aroma compounds, and minimizes carryover, meeting the demands of modern analytical laboratories.