Mineral Oil Residues in Food Sample Preparation - Part 3 - Fract and Collect

Importance of the Topic

Mineral oil hydrocarbon residues (MOSH/MOAH) are ubiquitous contaminants in food matrices, from grains and oils to packaging-derived sources. Their saturated and aromatic fractions can accumulate in human tissues and pose health risks, making accurate separation and detailed analysis essential for food safety and regulatory compliance.

Study Objectives and Overview

This work presents an automated LC–GC-FID method combined with a Fract & Collect tool to fractionate mineral oil saturated hydrocarbons (MOSH) and aromatic hydrocarbons (MOAH). The collected fractions are then available for in-depth GC-MS or comprehensive GC×GC-MS characterization, addressing limitations of total MOH quantification.

Methodology and Instrumentation

The workflow employs:

• Liquid Chromatography: Shimadzu LC-20AD with Allure Silica column (250×2.1 mm, 5 µm), using an n-hexane/dichloromethane gradient; UV detection at 230 nm.
• Fract & Collect Tool: Automated switching valve transfers MOSH and MOAH fractions into autosampler vials for downstream analysis.
• Gas Chromatography–FID: Shimadzu GC-2010 dual FID with Restek MXT-1 column (15 m×0.25 mm×0.1 µm), hydrogen carrier gas, and dual temperature programs for MOSH and MOAH detection.
• GC–MS: Shimadzu GCMS-TQ8050 triple quadrupole with Restek Rxi-5ms column (30 m×0.25 mm×0.25 µm), Q3 scan mode (50–400 amu) to profile molecular ions.

Main Results and Discussion

Applying the Fract & Collect procedure to a recycled paper sample yielded five pooled MOAH fractions concentrated to 500 µL. GC–MS analysis of extracted ions (m/z 218, 232, 246, 260, 274, 288) confirmed alkylated benzenes with C10–C15 chains. The LC chromatogram demonstrated clear separation of MOSH and MOAH, while the GC–FID trace provided total MOH quantification. Literature data indicate MOSH/MOAH levels in food range from 1.8–160 mg/kg in rice, 10–1200 mg/kg in fish (fat-based), 5–1300 mg/kg in cocoa and chocolate, up to 33 mg/kg in packaged baby food, and up to 6000 mg/kg in edible oils.

Benefits and Practical Applications

• Automates fraction collection to streamline sample preparation for advanced GC–MS analyses.
• Enables separate quantification and speciation of saturated versus aromatic hydrocarbons.
• Enhances regulatory compliance by providing detailed compositional data beyond total MOH levels.

Future Trends and Opportunities

Emerging integration with two-dimensional GC×GC-MS will further resolve complex hydrocarbon mixtures. Standardized protocols for MOSH/MOAH monitoring across diverse food matrices are expected to evolve. Advances in automation and data processing will support high-throughput screening and tighter regulatory limits.

Conclusion

The automated Fract & Collect LC–GC-FID approach delivers reliable separation and recovery of MOSH and MOAH fractions, facilitating comprehensive GC–MS analysis. This methodology improves analytical depth for food safety assessments and supports compliance with evolving regulatory standards.

References

1. Bundesinstitut für Risikobewertung (BfR), Statement No. 008/2010, December 9, 2010.
2. EFSA Panel on Contaminants in the Food Chain (CONTAM), EFSA Journal 2012;10(6):2704–2889.