Development of Vitamin E Analysis in Palm Oil

Significance of the Topic

Vitamin E homologues (tocopherols) play a vital role as antioxidants in palm oil and are key quality markers in food production. Traditional normal phase HPLC methods for quantifying these compounds involve lengthy runs and high consumption of toxic organic solvents. Supercritical Fluid Chromatography (SFC) using carbon dioxide offers a faster, more cost-effective, and environmentally friendly approach, aligning with the growing demand for high-throughput, green analytical methods in the food industry.

Aims and Study Overview

This work aimed to develop and validate an SFC method on the Shimadzu Nexera UC system for rapid quantification of four tocopherol homologues (alpha, beta, gamma, delta) in various palm oil samples. The performance of the SFC protocol was benchmarked against conventional normal phase HPLC in terms of analysis time, solvent usage, sensitivity, and reproducibility.

Methodology and Instrumentation

Sample Preparation:

• Palm oil types: crude, two refined extracts, and palm kernel oil.
• Dilution with n-hexane, vortex mixing for 3 min, followed by centrifugation (5 000 × g, 5 min).
• Filtration through 0.22 μm PTFE before analysis.

Instrumentation Used:

• SFC system: Shimadzu Nexera UC.
• Column: Shim-pack UC-X NH2 (250 mm × 2.1 mm I.D., 5 μm).
• Mobile phase: CO2 and methanol; gradient from 1.5 % to 20 % methanol (2.5–2.9 min), then return to 1.5 %.
• Flow rate: 4 mL/min; column temperature: 40 °C; back pressure: 15 MPa at 50 °C.
• Injection volume: 5 μL; detection by PDA at 292 nm (reference 500 nm).

Calibration and Validation:

• Alpha-tocopherol: 0.8–500 mg/L; other homologues: 0.8–100 mg/L.
• Repeatability: RSD ≤ 0.65 % (n = 6 at 100 mg/L).
• Linearity: correlation coefficients of 0.9999 for all four homologues.
• LOD: 0.4–0.7 mg/L.

Main Results and Discussion

The optimized SFC method achieved baseline separation of all four tocopherol homologues within 3 minutes, compared to over 15 minutes for normal phase HPLC. Calibration curves exhibited excellent linearity (r > 0.9999), and LOD values were below 1 mg/L. Quantitative analysis across four palm oil samples revealed that crude palm oil contained the highest alpha-tocopherol concentration (358.6 mg/L), with trace levels of beta, gamma, and delta forms in refined oils. The rapid run time and high sensitivity demonstrate the method’s suitability for routine quality control.

Benefits and Practical Applications

• Reduction of analysis time by approximately 80 % (3 min vs. 15 min).
• Substantial decrease in organic solvent use (n-hexane consumption from ~30 mL to negligible; CO2 cost is minimal).
• Lower operating costs due to inexpensive CO2 and reduced waste disposal.
• High throughput makes it ideal for large-scale screening in R&D and QC laboratories.
• Compatibility with mass spectrometry and fraction collectors for advanced applications.

Future Trends and Potential Applications

Integration of SFC with tandem mass spectrometry will enhance detection of minor lipophilic compounds in complex matrices. Automation of sample prep and coupling with online fraction collection can further streamline workflows in food analysis and pharmaceutical research. Expansion of SFC platforms to monitor other vitamin classes and plant-derived antioxidants will support broader adoption of green chromatography in industry.

Conclusion

The developed SFC method on the Shimadzu Nexera UC enables rapid, sensitive, and eco-friendly analysis of tocopherol homologues in palm oil. With superior throughput and dramatically reduced solvent use, this approach represents a practical alternative to normal phase HPLC for routine quality assessment in the food industry.