Analysis of MOSH and MOAH using SPE prior to GC×GC-MS analysis

Significance of the Topic

Mineral oil hydrocarbons, including MOSH and MOAH, are common contaminants in food products due to migration from paperboard packaging and recycled fibers. These compounds pose potential toxicological risks, especially MOAH, which may contain carcinogenic polyaromatic structures. Reliable analytical methods are essential for monitoring contamination levels, ensuring food safety, and complying with regulatory limits. Comprehensive two-dimensional gas chromatography coupled with dual detection provides detailed compositional information and accurate quantification, addressing the limitations of conventional one-dimensional techniques.

Objectives and Overview of the Study

This work aims to develop and optimize a GC×GC method with flame ionization detection and quadrupole mass spectrometry for the simultaneous identification and quantification of MOSH and MOAH in various food matrices. A pre-fractionation step using silver silica SPE cartridges is applied to separate saturated and aromatic fractions, preventing column and detector overload. The method is validated in terms of linearity, sensitivity, and reproducibility, and applied to real samples of pasta, icing sugar, and rice.

Methodology

Sample Preparation:

• Extraction: Ground food samples (pasta, rice, icing sugar) were extracted overnight with n-hexane (1:2 w/v).
• Clean-up: Extracts were purified on silver-silica SPE cartridges to fractionate MOSH and MOAH.
• Fractionation: MOSH eluted with n-hexane/n-dichloromethane mixtures; MOAH eluted with larger volume of 50:50 n-hexane/DCM.
• Concentration: Final extracts reduced to 100 µL for analysis.

Chromatographic Conditions:

• GC×GC System: Shimadzu GC-2010 with Zoex ZX1 two-stage thermal loop modulator.
• Columns: First dimension SLB-5ms (30 m × 0.25 mm × 0.25 µm), second dimension Supelcowax-10 (1 m × 0.10 mm × 0.10 µm).
• Oven Program: 50 °C to 280 °C at 4 °C/min, hold 7.5 min.
• Carrier Gas: Helium at 243 kPa, constant linear velocity.
• Injection: Pulsed split (1:10) at 360 °C, volume 6 µL.

Detection and Data Processing:

• Split Flow: 84% to FID, 16% to MS to balance sensitivity and chromatographic fidelity.
• FID: H₂ 40 mL/min, air 400 mL/min, He make-up 30 mL/min.
• MS: Shimadzu QP2010 Ultra, EI mode, full scan 40–510 m/z, 20 000 amu/sec, interface/source 250/200 °C.
• Quantification: Six-point calibration (0.35–24 mg/kg) using paraffin oil, LoQ ~1.2 mg/kg.
• Data Analysis: Polygonal integration enabled subtraction of non-target peaks; ChromSquare software for 2D visualization and peak deconvolution.

Used Instrumentation

• Shimadzu GC-2010 gas chromatograph
• Zoex ZX1 two-stage thermal modulator
• Shimadzu QP2010 Ultra quadrupole mass spectrometer
• Flame ionization detector (Shimadzu FID)
• Silver-silica SPE cartridges (Macherey-Nagel)

Main Results and Discussion

• The optimized dual-detection GC×GC method achieved resolution comparable to MS-only setups while allowing simultaneous FID quantification.
• Calibration showed excellent linearity (R² = 0.9993) and method sensitivity with an LoQ around 1.2 mg/kg.
• Quantitative analysis of food samples yielded MOSH (
• GC×GC-MS tentatively identified over 25 unknown compounds in the MOAH fractions, mainly esterified fatty acids from vegetable-based printing inks, alongside n-alkanes, ketones, and phthalates.
• Differences in contamination profiles suggested direct ink contact in pasta packaging and recycled fiber contributions in the other samples.

Benefits and Practical Applications

• Enables comprehensive profiling of MOSH and MOAH for risk assessment and regulatory compliance.
• Dual FID/MS detection integrates sensitive quantification with structural elucidation in a single workflow.
• Silver-silica SPE pre-separation prevents column overload and enhances the specificity of second-dimension analysis.
• Polygonal integration facilitates accurate exclusion of interfering peaks and complex matrix components.

Future Trends and Potential Applications

• Development of standardized 2D retention index libraries for more reliable compound identification.
• Integration of high-resolution MS detectors to improve structural characterization of MOAH constituents.
• Automation of SPE and GC×GC workflows for higher throughput in routine food safety laboratories.
• Extension of the method to other hydrocarbon contaminants, such as environmental pollutants and petrochemical residues.

Conclusion

The optimized GC×GC-FID/MS method with silver-silica SPE fractionation provides a robust and sensitive approach for simultaneous identification and quantification of MOSH and MOAH in food matrices. It offers detailed compositional insights, supports contamination source tracking, and meets current analytical demands for food safety monitoring.

References

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