Antioxidants in Edible Oils by AOAC 983.15 on a Thermo Scientific™ Acclaim™ 120 C18 Column

Importance of the Topic

The analysis of synthetic antioxidants in edible oils is critical to ensure product quality, shelf life and consumer safety. Rancidity in oils not only degrades flavor and aroma but can also generate harmful byproducts. A standardized, reliable method for quantifying these preservatives supports regulatory compliance and industrial quality control.

Objectives and Study Overview

This work evaluates a modified AOAC 983.15 assay for the simultaneous determination of nine approved antioxidants in wheat germ oil using high-performance liquid chromatography. The goal is to demonstrate complete separation and confident identification of each compound in a complex oil matrix.

Methodology and Instrumentation

The sample consisted of wheat germ oil spiked with the following antioxidants:

• Propyl gallate
• Trihydroxybutyrophenone (THBP)
• t-Butylhydroquinone (TBHQ)
• Nordihydroguiaretic acid (NDGA)
• Butylated hydroxyanisole (BHA)
• Ionox-100
• Octyl gallate
• Butylated hydroxytoluene (BHT)
• Dodecyl gallate

The chromatographic system employed a Thermo Scientific™ Acclaim™ 120 C18 column (4.6 × 150 mm, 5 μm). The mobile phase consisted of (A) 0.75% acetic acid in water and (B) a 50:50:0.5 mixture of methanol, acetonitrile and acetic acid. A gradient program from 30% A/70% B to 100% B over 9.6 minutes, with a flow increase to 4.0 mL/min at 12.0 minutes, was used. Injection volume was 10 μL. Detection was performed at 280 nm UV with diode array confirmation to verify peak identity.

Main Results and Discussion

Under the optimized conditions, all nine antioxidants were baseline-separated within a 15-minute run time. The diode array detector provided spectral confirmation even in the presence of co-extractives from wheat germ oil. Ethoxyquin, although not shown in the chromatogram, was also resolved under the same conditions. Peak elution order matched the standard sequence:

1. Propyl gallate
2. THBP
3. TBHQ
4. NDGA
5. BHA
6. Ionox-100
7. Octyl gallate
8. BHT
9. Dodecyl gallate

The method exhibited sharp peaks and reproducible retention times, demonstrating robustness for routine analysis.

Benefits and Practical Applications

This assay offers several advantages:

• Rapid analysis suitable for high-throughput quality control.
• Compatibility with complex oil matrices.
• Spectral confirmation enhances confidence in peak identification.
• Alignment with official AOAC standards facilitates regulatory acceptance.
• Minimal sample preparation accelerates workflow.

Future Trends and Potential Applications

Emerging developments could include coupling to mass spectrometry for enhanced selectivity, adoption of greener solvents to reduce environmental impact, and further miniaturization of the chromatographic system. Real-time process monitoring and integration into automated laboratory platforms may also expand the method’s utility in industrial settings. The approach can be adapted to other edible oil types and antioxidant additives.

Conclusion

The modified AOAC 983.15 method using an Acclaim 120 C18 column provides a fast, reliable and fully validated assay for nine common antioxidants in edible oils. Its robust performance and spectral confirmation capability make it an excellent choice for routine quality control and regulatory compliance.