Determination of MCPD and glycidyl esters in foodstuff

Significance of the Topic

Monochloropropanediol (MCPD) and glycidol esters form in refined fats and oils under high temperature or in the presence of chloride salts and are considered potential carcinogens. Regulatory limits, such as the EFSA tolerable daily intake of 0.8 µg per kg body weight, drive the need for precise and efficient analytical methods to ensure food safety.

Objectives and Study Overview

This work aims to automate the indirect gas chromatography–mass spectrometry method AOCS Cd 29c-13 (DGF C-VI 18(10)) for quantifying 2-MCPD, 3-MCPD and glycidol in foodstuffs. Key goals include reducing manual intervention, boosting sample throughput, and maintaining robust performance and accuracy.

Methodology and Instrumentation

• Sample preparation uses a two-part transesterification: Part A releases both MCPD and glycidol esters into free MCPD; Part B selectively releases MCPD esters only. The difference yields glycidol concentration.
• Automation is achieved on a PAL DHR Dual Head system under CHRONOS software. Key modules include solvent stations, vortex mixer, centrifuge, wash stations and a dilutor module for precise reagent delivery.
• GC-MS analysis employs a Bruker EVOQ GC-TQ equipped with a backflush option to prevent carryover of derivatization reagents. Multiple reaction monitoring transitions were optimized for each analyte and its deuterated internal standard.

Key Results and Discussion

• Validation in an olive oil blank matrix delivered recoveries of 94–133% and a detection limit of 0.026 mg per kg for 3-MCPD.
• The DGF Fast & Clean variant achieved recoveries of 91–116%, matching classical method performance with reduced analysis time.
• The automated workflow completes both parts A and B in 45 minutes per sample, enabling up to 36 samples per 24-hour period.
• Comparisons with manual methods and the SGS 3-in-1 approach showed agreement within 10% for all analytes.
• Chromatographic reproducibility was confirmed by ten consecutive injections showing consistent retention times and peak areas.

Benefits and Practical Applications

• Full automation minimizes human error and accelerates routine laboratory operations.
• High throughput supports stringent QA/QC demands in food analysis environments.
• Modular system design allows adaptation to additional contaminant assays in fats and oils.
• Backflush cleaning extends GC-MS uptime beyond 200 injections, improving instrument utilization.

Future Trends and Opportunities

• Integration of direct LC-MS methods may complement this GC-MS workflow for detailed profiling of individual esters.
• Further miniaturization and robotics integration could reduce solvent consumption and operational costs.
• Application of high-resolution mass spectrometry may reveal unknown process contaminants in complex matrices.
• Development of in-line monitoring systems for real-time control of refining processes.

Conclusion

The automated indirect GC-MS method based on AOCS Cd 29c-13 provides a rapid, accurate and robust solution for determining MCPD and glycidyl esters in refined oils and fats. The PAL DHR Dual Head system under CHRONOS control substantially enhances throughput and reproducibility, fulfilling modern food safety laboratory requirements.

Reference

1. Zwagerman R and Overman P. Method for automatic sample preparation and analysis of 3-MCPD, 2-MCPD and glycidyl esters in edible oils and fats. European Journal of Lipid Science and Technology. 2016;118:997–1006.
2. Official AOCS Method Cd 29c-13. Fatty-Acid Bound 3-Chloropropane-1,2-Diol and 2,3-Epoxy-Propane-1-ol Determination by GC-MS. Approved 2013.
3. Official AOCS Method Cd 29b-13. Determination of Bound Monochloropropanediol and Bound Glycidol by GC-MS. Approved 2013.
4. Official AOCS Method Cd 29a-13. 2- and 3-MCPD Fatty Acid Esters and Glycidol Esters by Acid Transesterification. Approved 2013.
5. Kuhlman J. Determination of bound glycidol and MCPD in refined oils. European Journal of Lipid Science and Technology. 2011;113:335–344.