Analysis of 3-monochloropropanediol, 3-MCPD fatty acid ester and Glycidyl Ester in Infant Formula based on AOAC Official Methods 2018.12

Importance of the Topic

Monochloropropanediols (MCPDs) and glycidyl esters are process-related contaminants formed during refinement and heating of edible oils. In infant formula, free MCPDs and their fatty acid esters may pose health risks, including renal damage and endocrine disruption. Regulatory authorities, such as EFSA, call for robust analytical methods to monitor these compounds and ensure product safety.

Objectives and Study Overview

This work evaluates the AOAC Official Method 2018.12 for the simultaneous quantification of free 3-MCPD, 3-MCPD fatty acid esters, and glycidyl esters in powdered infant formula. An alternative in-house SIM/MRM GC-MS protocol is also compared. Key goals include method performance assessment, calibration range validation, and practical applicability to real samples.

Methodology and Instrumentation

Two analytical workflows were developed:

• AOAC Official Method 2018.12: Sample extraction of powdered milk using methanol, methyl tert-butyl ether and saponification for ester hydrolysis, followed by liquid-liquid partitioning and derivatization of free MCPDs with phenylboronic acid.
• Original SIM/MRM Method: Similar extraction and derivatization steps, with targeted monitoring of free and converted analytes using GC-MS/MS (SIM and MRM modes).

Instrumentation details:

• GC-MS System: Shimadzu GCMS-TQ-8050 NX (triple quadrupole) and QP-2020 NX.
• Columns: SH-5MS (50% phenyl/50% dimethylpolysiloxane, 30 m × 0.25 mm × 0.25 µm) and Rxi-17 (50% diphenyl/50% dimethylpolysiloxane).
• Inlet Configurations: Split injection and programmable temperature vaporization (PTV).
• Detection Modes: SIM for free MCPDs, MRM transitions for 3-MCPD (147→91) and 3-MBPD (242→147).

Main Results and Discussion

Calibration curves exhibited excellent linearity over 10–1000 ppb for free 3-MCPD and 50–1000 ppb for 3-MBPD, with correlation coefficients (R2) ≥ 0.996. The LOQ for free 3-MCPD was around 10–14 ppb, enabling sensitive detection in the aqueous extract of formula samples. The SH-5MS column delivered sharper peaks but showed gradual stationary phase deterioration when cleanup was insufficient or derivatizing reagent excess occurred. The PTV inlet improved impurity management but may accumulate nonvolatile residues.

Benefits and Practical Applications

Both methods allow reliable quantification of MCPD-related contaminants in infant formula, supporting:

• Quality assurance and regulatory compliance testing.
• Routine monitoring of process-induced impurities.
• Risk assessment studies for vulnerable populations.

Future Trends and Opportunities

Advancements may include high-resolution MS for enhanced selectivity, automated on-line sample cleanup, application of supercritical fluid chromatography for reduced solvent use, and extension to other food matrices or environmental samples.

Conclusion

The AOAC Official Method 2018.12 and the custom SIM/MRM GC-MS protocol both demonstrate robust performance for the determination of 3-MCPD, its esters, and glycidyl esters in infant formula. Laboratories can select the approach that best balances sensitivity, peak quality, and maintenance considerations to maintain product safety.

References

AOAC Official Method 2018.12: Determination of 3-Monochloropropanediol and Glycidyl Fatty Acid Esters in Edible Oils and Related Products.
EFSA Scientific Opinion on Contaminants in the Food Chain.