Oxygen heterocyclic compounds profile evaluation in cold-pressed Citrus essential oils using supercritical fluid chromatography coupled to photodiode array detector

Importance of the Topic

The non-volatile fraction of cold-pressed Citrus essential oils contains oxygen heterocyclic compounds such as coumarins, psoralens and polymethoxyflavones that impact oil quality, authenticity and safety, particularly in cosmetic applications due to potential photoactivity.

Objectives and Study Overview

This study aimed to develop a rapid, environmentally friendly supercritical fluid chromatography method with photodiode array detection (SFC-PDA) to profile 37 oxygen heterocyclic compounds in seven cold-pressed Citrus essential oils within a 10-minute run time.

Instrumentation Used

The analysis employed a Shimadzu Nexera UC SFC-PDA system comprising dual LC pumps, a CO₂ pump, backpressure regulator, column oven, autosampler and photodiode array detector, configured for HILIC separations.

Methodology

A fused-core HILIC column (150 × 2.1 mm, 2.7 μm) was used with supercritical CO₂ and ethanol (0.6 % water, 0.07 % TFA) gradient. Flow rate was 1.0 mL/min, column temperature 60 °C, backpressure 120 bar and detection at 315 nm. Samples of lime, lemon, bergamot, grapefruit, sweet and bitter oranges, and red mandarin oils were analyzed after 1:1000 dilution in hexane.

Main Results and Discussion

The SFC-PDA method achieved baseline separation of 37 target compounds in under 10 minutes. Comparison via AGREE metrics demonstrated significant green benefits over traditional RP-HPLC-PDA, including a 20-fold reduction in organic solvent waste, lower energy use and replacement of toxic solvents with ethanol from renewable sources.

Benefits and Practical Applications

• Rapid profiling for quality control and authentication of Citrus oils in cosmetics and food industries
• Enhanced laboratory sustainability through reduced solvent consumption and waste
• High sensitivity and reproducibility suitable for routine analysis

Future Trends and Potential Applications

Further work could integrate mass spectrometry detection to expand compound identification, extend SFC-PDA profiling to other plant matrices and drive broader adoption of green chromatographic techniques in industrial laboratories.

Conclusion

The developed SFC-PDA approach provides a fast, sensitive and eco-friendly tool for comprehensive analysis of oxygen heterocyclic compounds in cold-pressed Citrus essential oils, supporting quality control and regulatory compliance in cosmetic and related sectors.

References

1. European Parliament and Council Regulation (EC) No. 1223/2009 on cosmetic products, Official Journal of the European Union L 342 (2009) 59.
2. International Fragrance Association, IFRA Standard 48th Amendment – Citrus oils and furocoumarin-containing essential oils (2015).
3. International Fragrance Association, IFRA HPLC-DAD method for quantitative furocoumarin determination (2013).
4. European Parliament and Council Regulation (EC) No 1334/2008 on flavorings and food ingredients (2008) L 354 (34).
5. Russo M., Rigano F., Arigò A., Dugo P., Mondello L., Coumarins, Psoralens and Polymethoxyflavones in Cold-pressed Citrus Essential Oils: a Review, Journal of Essential Oil Research (2021), DOI:10.1080/10412905.2020.1857855.
6. Pena-Pereira F., Wojnowski W., Tobiszewski M., AGREE – Analytical Greenness Metric Approach and Software, Analytical Chemistry (2020), DOI:10.1021/acs.analchem.0c01887.
7. Russo M., Bonaccorsi I., Costa R., Trozzi A., Dugo P., Mondello L., Reduced Time HPLC Analyses for Fast Quality Control of Citrus Essential Oils, Journal of Essential Oil Research (2015), DOI:10.1080/10412905.2015.1027419.