Simultaneous Determination of MOSH and MOAH Fractions by means of online 2-channel HPLC-LV-GC-FID

Importance of the Topic

The migration of mineral oil into foodstuffs from recycled packaging raises safety and regulatory concerns. Accurate quantification of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) is essential for food quality control, consumer protection and compliance with emerging guidelines in food safety.

Objectives and Overview

This work aimed to optimize an existing two-step HPLC-GC-FID method into a single, online two-channel HPLC-large-volume-GC-FID run. By adapting the retention gap technique and parallel detection, the method doubles sample throughput, reduces solvent consumption and simplifies laboratory workflows while maintaining analytical performance.

Methodology

Sample preparation relies on hexane extraction adapted to matrix characteristics (fat, moisture). The workflow comprises:

1. Injection of a 450 µL hexane extract onto a normal-phase HPLC column to separate MOSH and MOAH fractions from lipids and other interferences.
2. Use of two large-volume injection channels and retention gaps to trap the early-eluting MOSH fraction until the MOAH fraction is ready for transfer.
3. Simultaneous transfer of both fractions to two parallel GC-FID detectors, enabling concurrent detection and cumulative signal evaluation.

Instrumentation

• Binary normal-phase HPLC pump (Agilent)
• Two-channel large-volume GC injector
• DANI Master GC with two flame ionization detectors
• CTC CombiPAL autosampler
• Control and data acquisition software: Chronos 3.1 and Clarity 3.0

Results and Discussion

Validation experiments using a BAM lubricating oil standard (4–250 µg/mL) yielded linear calibration curves for MOSH (R² = 0.9985) and MOAH (R² = 0.9988) across a wide dynamic range. The method demonstrated:

• Analysis time of 30 minutes per sample, including GC run and system reconditioning.
• Limit of quantification down to 4 µg/mL with good precision.
• Repeatability for a rice sample MOSH fraction with 5.8% RSD (n = 6).

The approach avoids additional concentration steps, maintains clear fraction separation and leverages the substance-independent response of FID for reliable quantification.

Applications and Benefits

This streamlined technique is well suited for routine monitoring of food and packaging materials in quality assurance and regulatory laboratories. Key advantages include reduced manual intervention, lower solvent use, higher sample throughput and simplified calibration strategies based on internal standards.

Future Trends and Possible Uses

Emerging developments may focus on coupling this platform with mass spectrometric detection for structural confirmation and lower detection limits. The integration of automated sample preparation, miniaturized chromatography and standardized MOAH reference materials will further enhance robustness and applicability in regulatory settings and industrial quality control.

Conclusion

The presented online two-channel HPLC-LV-GC-FID method enables simultaneous, accurate analysis of MOSH and MOAH in a single run. It offers significant improvements in efficiency, environmental impact and data quality, supporting comprehensive monitoring of mineral oil contaminants in food and packaging.

Reference

Biedermann M., Fiselier K., Grob K. Journal of Agricultural and Food Chemistry 2009, 57, 8711–8721.