Determination of mineral oil aromatic hydrocarbons (MOAH) in food by LC GC FID – Comparison of conventional vs. automated epoxidation

Importance of the topic

Mineral oil hydrocarbons represent a common contamination in food, comprising saturated (MOSH) and aromatic fractions (MOAH). MOAH is of particular concern due to potential carcinogenic effects and analytical challenges posed by coextractives like squalene and sterenes, which interfere with standard detection methods.

Objectives and study overview

This work compares a conventional manual epoxidation protocol using m-CPBA in dichloromethane under subambient conditions with a novel fully automated epoxidation in ethanol/n-hexane at room temperature. The goal is to evaluate precision, recovery, and interference removal in LC-GC-FID analysis of MOAH in food matrices.

Methodology and instrumentation

• Sample extraction with n-hexane and clean-up by silica gel column elution
• Conventional epoxidation using m-CPBA in dichloromethane with cooling and quenching by sodium bicarbonate
• Automated epoxidation adding ethanolic m-CPBA, quenching with sodium thiosulfate, shaking and centrifugation inside an autosampler
• Detection by LC-GC-FID with a 1260 Infinity HPLC, a 7890B GC-FID, DualPAL autosampler and CHRONECT LC-GC interface

Key results and discussion

• Repeatability below 1.1 percent and recoveries between 94 and 103 percent for both methods
• Automated epoxidation markedly reduced squalene and other interferences in maize and olive oil chromatograms
• MOAH concentrations determined by both methods were comparable: maize oil 11.7 ppm and olive oil 7.4 to 7.8 ppm

Benefits and practical applications

The automated approach simplifies sample preparation by eliminating low temperature steps, volatile solvent evaporation and reconstitution, while ensuring quantitative recovery of MOAH. It enhances routine laboratory throughput and reduces risk of misinterpretation from residual interferences.

Future trends and opportunities

• Extension of automated epoxidation to diverse food and environmental matrices
• Integration into high throughput quality control and monitoring workflows
• Adaptation for analysis of related hydrocarbon contaminants and further reduction of matrix effects

Conclusion

Automated epoxidation in ethanol/n-hexane provides an effective alternative to conventional methods, delivering equivalent accuracy and recovery of MOAH with improved selectivity and operational efficiency suitable for routine LC-GC-FID analysis.

Reference

1. Barp L Kornauth C Wuerger T Rudas M Biedermann M Reiner A Concin N Grob K Food Chem Toxicol 2014 72 312–321
2. Biedermann M Grob K J Chromatogr A 2015 1375 136–153
3. Biedermann M Fiselier K Grob K J Agric Food Chem 2009 57 8711–8721
4. CEN TC 275 N 1069
5. Nestola M Schmidt TC J Chromatogr A 2017 1505 69–76