SIM and MRM Analysis of 3-MCPD, 3-MCPD Fatty Acid Esters, and Glycidol Fatty Acid Esters in Powdered Milk

Importance of the Topic

Monitoring chlorine-containing contaminants such as 3-monochloropropane-1,2-diol (3-MCPD), its fatty acid esters and glycidol fatty acid esters in powdered milk is critical due to potential health risks. Regulatory bodies are tightening limits in infant formulas, and reliable analytical methods are needed to ensure food safety and compliance.

Objectives and Study Overview

This study demonstrates a unified procedure for simultaneous analysis of free 3-MCPD, 3-MCPD fatty acid esters and glycidol fatty acid esters in powdered milk. Using a single sample preparation workflow based on AOAC Official Method 2018.12 and a GC-MS/MS system, the aim was to evaluate sensitivity, selectivity and robustness under SIM and MRM acquisition modes.

Instrumental Setup

• GC-MS/MS system: GCMS-TQ8050 NX triple quadrupole
• Column: SH-5MS (30 m × 0.25 mm, 0.25 μm film)
• Injection: split 20:1 at 250 °C
• Oven program: 50 °C (20 min) to 300 °C at 10 °C/min, hold 3 min
• Ionization: EI, source 200 °C, interface 300 °C
• Carrier gas: helium at linear velocity 50 cm/s
• Acquisition: SIM for screening, MRM for greater selectivity

Methodology and Sample Preparation

• Weigh 2 g powdered milk and extract with MeOH; repeat extraction with MeOH/MTBE (1:1) and MTBE; combine and dry under N₂.
• Dissolve residue in saturated Na₂SO₄ solution; perform two liquid–liquid partitions with hexane/MTBE (4:1).
• For free 3-MCPD, extract aqueous layer with diethyl ether thrice, add phenylboronic acid derivatization, dry and reconstitute in isooctane.
• For ester-bound analytes, dissolve organic layer in MTBE, saponify with NaOH/MeOH at –25 °C, neutralize with NaBr/H₃PO₄, remove upper hexane phase, derivatize lower layer with phenylboronic acid.
• Use d-3-MCPD as internal standard; calibration curves prepared at relevant ppb levels.

Main Results and Discussion

• Free 3-MCPD was detected at about 15 ppb in powdered milk; calibration linearity (R²>0.999) achieved for 50–1000 ppb.
• Fatty acid esters and glycidol esters were quantified down to 10 ppb; SIM S/N at 10 ppb exceeded 100, MRM S/N exceeded 200.
• MRM mode reduced matrix interference and improved selectivity compared to SIM, while maintaining similar sensitivity.
• Robust performance of GCMS-TQ8050 NX enabled reproducible quantitation under high-throughput conditions.

Benefits and Practical Applications

• Single sample preparation for multiple target analytes simplifies workflow.
• MRM acquisition ensures reliable quantification in complex food matrices.
• Compliance with EFSA and AOAC guidelines supports regulatory requirements.
• Method can be extended to related analytes such as 2-MCPD and glycidol in diverse food products.

Future Trends and Applications

• Adoption of isotopically labeled fatty acid ester standards for improved accuracy.
• Automation of sample pretreatment and online derivatization to increase throughput.
• Integration with high-resolution MS for simultaneous screening of emerging chloropropanols.
• Expansion to other dairy and oil-rich matrices to support broad food safety monitoring.

Conclusion

The combination of a streamlined AOAC-based sample preparation and GC-MS/MS in MRM mode provides a sensitive, selective and robust solution for monitoring 3-MCPD and its esters in powdered milk. This approach ensures compliance with tightening regulations and supports routine quality control in the dairy industry.

References

• AOAC Official Method 2018.12 “2-Monochloropropanediol (2-MCPD), 3-Monochloropropanediol (3-MCPD), and Glycidol in Infant and Adult/Pediatric Nutritional Formula”