Quantitative Analysis of Tocopherols in Vegetable Oils

Significance of the topic

The quantitative determination of tocopherols (vitamin E analogs) in vegetable oils is critical for nutritional labeling, quality control, and assessing antioxidant capacity. Traditional normal-phase liquid chromatography methods require extensive run times and high volumes of organic solvents. Supercritical fluid chromatography (SFC) offers faster separations and lower solvent usage, aligning with green analytical chemistry goals.

Objectives and study overview

This application note demonstrates a rapid SFC-based method for the simultaneous quantification of α-, β-, γ- and δ-tocopherol in various vegetable oils. Using Shimadzu’s Nexera UC system, the study aims to achieve baseline resolution of all four homologs within four minutes while reducing solvent consumption and operational costs.

Methodology and Instrumentation

500 μL aliquots of sunflower, olive, palm and sesame oils were diluted in n-hexane and vortex-mixed prior to analysis. A mixed standard solution (50 mg/L each homolog) in n-hexane served for calibration.

Used instrumentation

• System: Shimadzu Nexera UC SFC
• Column: Shim-pack UC-NH2 (250 mm × 4.6 mm I.D., 5 μm)
• Mobile phase: CO2 (A) and methanol (B) with a gradient from 3% to 50% B over 5 minutes, returning to 3% at 7.01 minutes
• Flow rate: 5.0 mL/min
• Column temperature: 40 °C; back-pressure regulator (BPR) at 15 MPa and 50 °C
• Injection volume: 20 μL
• Detection: UV at 295 nm (high-pressure flow cell)

Main results and discussion

Calibration curves for all tocopherol forms exhibited excellent linearity (r2 ≥ 0.9995) across concentration ranges tailored to expected sample levels. Chromatographic resolution allowed full separation of four peaks within four minutes.

Quantitative analysis of oils revealed:

• Sunflower oil: high α-tocopherol (~53 mg/100 g) and low β-tocopherol (~1.3 mg/100 g)
• Olive oil: moderate α-tocopherol (~13 mg/100 g)
• Palm oil: detectable γ- and δ-tocopherol (5–8 mg/100 g) with lower α-tocopherol (~8 mg/100 g)
• Sesame oil: significant γ- (33 mg/100 g) and δ-tocopherol (~13 mg/100 g), plus ~10 mg/100 g α-tocopherol

The SFC approach reduced analysis time by >60% compared to conventional NPLC while maintaining comparable peak resolution. CO2 as the primary mobile phase component dramatically lowers organic solvent usage and disposal costs.

Benefits and practical applications

• High throughput: complete tocopherol profile in ~4 minutes per run
• Cost savings: minimal methanol and elimination of large-volume hexane use
• Environmental advantage: CO2 is a greener alternative reducing hazardous waste
• Quality control: robust method suitable for routine analysis in research, production and regulatory laboratories

Future trends and potential applications

Emerging developments may include coupling SFC with mass spectrometry for enhanced sensitivity and selectivity, expanding applications to other lipid classes and fat-soluble vitamins. Continuous improvements in column chemistries and instrument automation will further streamline high-throughput, green analyses in food and nutraceutical industries.

Conclusion

The Nexera UC SFC method provides a rapid, reliable, and eco-friendly solution for tocopherol quantification in vegetable oils. Its speed, solvent reduction, and excellent chromatographic performance make it an attractive alternative to traditional NPLC techniques.