Sterols in rapeseed oil - Analysis of sterols in rapeseed oil as silyl derivatives

Significance of the Topic

Analysis of sterol profiles in rapeseed oil is essential for verifying oil authenticity, assessing nutritional value, and ensuring compliance with quality and safety regulations. Sterols also serve as biomarkers for oil processing, refinement stage, and origin verification.

Objectives and Study Overview

This study presents a streamlined gas chromatographic method for the rapid separation and quantification of major free sterols in rapeseed oil. The aim is to achieve baseline resolution of six endogenous sterols and one deuterated internal standard within an 11-minute run time, suitable for routine quality control laboratories.

Methodology

The sample preparation involves:

• Saponification of 1 g oil with aqueous NaOH at 120 °C.
• Addition of internal standard (avenasterol-D5) in 1-butanol.
• Liquid-liquid extraction and cleanup on neutral alumina.
• Evaporation and silylation with MSTFA/TMCS in MTBE.

Chromatographic conditions:

• Column: Agilent VF-5ht, 30 m × 0.25 mm, 0.1 μm film.
• Temperature program: 240 °C to 260 °C at 4 °C/min, then to 300 °C at 8 °C/min, hold 8 min.
• Injector: Split 1:20 at 320 °C, 1 μL injection.
• Carrier gas: Helium.
• Detector: Flame ionization (FID).

Main Results and Discussion

The method achieved clear separation of cholestane, cholesterol, brassicasterol, campesterol, stigmasterol, sitosterol, and avenasterol-D5 within 11 minutes. Retention times were reproducible with low relative standard deviations. The use of a high-temperature VF-5ht column enabled efficient elution of high-boiling sterol derivatives.

Benefits and Practical Applications

This rapid GC-FID approach offers:

• High throughput suitable for large sample batches.
• Robust quantification with an internal standard.
• Minimal solvent and reagent use after cleanup.
• Applicability in food testing, nutritional labeling, and authenticity screening.

Future Trends and Potential Applications

Emerging directions include coupling to mass spectrometry for structural confirmation, automated sample preparation for higher throughput, expansion to minor sterols and stanols, and adoption of greener extraction reagents. Integration with chemometric tools can enhance adulteration detection and origin classification.

Conclusion

The described GC-FID method provides a fast, reliable, and reproducible tool for sterol analysis in rapeseed oil. It meets routine analytical demands for quality control, authenticity verification, and regulatory compliance in the edible oil industry.

References

1. Agilent Technologies, Inc. Application Note A02423, “Sterols in Rapeseed Oil: Analysis as Silyl Derivatives,” 2011.