Determining MOSH/MOAH with GCxGC-TOFMS

Importance of the Topic

Mineral oil hydrocarbons (MOSH and MOAH) are recognized food contaminants with potential health risks flagged by EFSA. High chromatographic resolution is critical to separate these compounds from natural food constituents.

Study Objectives and Overview

This work demonstrates a comprehensive GC×GC-TOFMS workflow using the LECO Pegasus BT 4D system to confirm the presence of MOSH/MOAH in cumin. The study compares contaminated spice extracts with a VGO-IS petroleum standard to validate analytical performance.

Methodology and Instrumentation

The analytical approach involved direct LC-GC fractionation followed by two-dimensional gas chromatography and time-of-flight mass spectrometry. Key parameters:

• Modulator: LECO QuadJet thermal modulator, modulation period 5 s
• Injection: 2 µL splitless at 330 °C
• Columns: Rxi-17 SilMS (12 m × 0.25 mm × 0.25 µm), secondary Rxi-1-HT (1.05 m × 0.25 mm × 0.25 µm)
• Carrier gas: Helium at 1 mL/min
• Oven program: 40 °C (1 min), ramp 5 °C/min to 360 °C (10 min hold), secondary oven +7 °C offset
• MS detection: LECO Pegasus BT 4D, ion source 280 °C, mass range 40–700 amu, 200 spectra/s

Main Results and Discussion

The VGO-IS reference contour plot revealed well-resolved chemical classes such as n-paraffins, POSH, hopanes (m/z 191), and steranes (m/z 217). The cumin MOSH fraction showed hopane markers confirming mineral oil contamination, while the MOAH fraction displayed diisopropylnaphthalenes and dibenzothiophenes likely from packaging. Classification of mono, di and tri aromatic hydrocarbons was achieved, and naturally occurring sesquiterpenes like γ-amorphene were identified, demonstrating interference assessment.

Benefits and Practical Applications

• Enhanced resolution minimizes false positives from biogenic interferents
• High-confidence detection of trace contaminants such as hopanes and steranes
• Ability to classify specific hydrocarbon classes supports regulatory compliance

Future Trends and Applications

Ongoing work includes expanding the method to diverse matrices, integrating FID quantification, and developing dedicated software tools to streamline MOSH/MOAH analysis workflows.

Conclusion

GC×GC-TOFMS on the LECO Pegasus BT 4D platform offers a robust confirmatory method for MOSH/MOAH detection in food, improving specificity and reducing analytical biases compared to conventional GC-FID techniques.

References

• Scientific Opinion on Mineral Oil Hydrocarbons in Food EFSA Journal 2012;10(6):2704 DOI 10.2903/j.efsa.2012.2704
• EFSA Technical Report Rapid risk assessment infant formula contamination by MOAH EN-1741 2019