Fully Automated Determination of 3-MCPD and Glycidol in Edible Oils by GC/MS Based on the Commonly Used Methods ISO 18363-1, AOCS Cd 29c-13, and DGF C-VI 18 (10)

Significance of the Topic

Process-related contaminants 3-monochloropropanediol (3-MCPD) and glycidol, including their fatty acid esters, are formed during high-temperature refining of edible oils. Both compounds are of toxicological concern, with glycidol classified as a probable human carcinogen and 3-MCPD as a possible carcinogen. Regulatory bodies have defined maximum levels and tolerable daily intakes, driving the need for reliable, high-throughput analytical methods for routine quality control and food safety monitoring.

Objectives and Study Overview

This work aims to develop and validate a fully automated sample preparation and GC/MS workflow for the indirect determination of 3-MCPD and glycidol in edible oils, based on established methods ISO 18363-1, AOCS Cd 29c-13 and DGF C-VI 18 (10). The approach splits each sample into two assays (A and B) to obtain differential measurements and allows calculation of individual compound concentrations with minimal manual intervention.

Methodology

The automated procedure comprises:

• Weighing 100 mg oil and addition of internal standard solution and solvents.
• Alkaline transesterification (saponification) with MeOH/NaOH.
• Assay-specific quenching: acidic NaCl for assay A (converts glycidol to 3-MCPD) and NaBr for assay B (prevents conversion).
• Liquid–liquid extraction with hexane and MTBE/ethyl acetate; drying over sodium sulfate.
• Derivatization with phenylboronic acid followed by automated evaporation to dryness to remove excess reagent.
• Reconstitution in isooctane and GC/MS analysis using programmed temperature vaporization and SIM detection.

Used Instrumentation

The automated workflow employs a GERSTEL MultiPurpose Sampler (MPS) with DualHead configuration, incorporating:

• QuickMix module for vigorous shaking during extraction steps.
• mVap evaporator for controlled solvent removal and derivatization cleanup.
• Cooled Injection System 4 (CIS 4) for solvent-vent PTV injection.
• Gas chromatograph (Agilent 7890) coupled to a single quadrupole mass spectrometer (Agilent 5977 MSD) operated in selected ion monitoring (SIM) mode.

Main Results and Discussion

Conversion efficiency of glycidol to 3-MCPD in assay A was determined by spiking blank oil with glycidyl stearate at five levels; a linear regression yielded a conversion factor (t) with R² > 0.9998. Linearity studies for both assays over 0.12–1.9 mg/kg demonstrated excellent correlation (R² > 0.9998).

Analysis of three commercial edible oils showed good agreement with reference values:

• 3-MCPD levels: 0.27–0.77 mg/kg (automated vs. reference within ±0.1 mg/kg).
• Glycidol levels (calculated by difference): 0.11–0.44 mg/kg (automated vs. reference within ±0.13 mg/kg).

Repeatability over five replicate preparations yielded relative standard deviations of 5.0 % for 3-MCPD and 6.4 % for glycidol, demonstrating robust performance of the fully automated workflow.

Benefits and Practical Applications

The presented automation provides:

• Reduced manual handling and risk of contamination.
• Consistently low detection limits using a single quadrupole MSD.
• Improved laboratory throughput and reproducibility.
• Enhanced system stability by removing excess derivatization reagent prior to GC/MS.

This approach is suitable for routine QC in edible oil refining, food safety laboratories, and CROs performing regulatory compliance testing.

Future Trends and Applications

The automation platform can be extended to:

• Simultaneous analysis of 3-MCPD, glycidol and 2-MCPD in a 3-in-1 workflow.
• Automated cleanup and determination of polycyclic aromatic hydrocarbons (PAHs) in oils.
• Adaptation to direct LC/MS methods for comprehensive profiling of chloropropanediol and glycidyl esters.

Conclusion

The indirect ISO 18363-1/AOCS Cd 29c-13/DGF C-VI 18 method for 3-MCPD and glycidol analysis has been successfully automated on a GERSTEL MPS platform. The workflow delivers accurate, precise and high-throughput determination of both contaminants, meeting regulatory requirements and improving laboratory efficiency.

Reference

1. Bundesinstitut für Risikobewertung (BfR). Information on contamination of foods with 3-MCPD, 2-MCPD and glycidyl fatty acid esters. 2016.
2. DGF C-VI 18 (10). Determination of bromopropanediols and monochloropropanediols in edible oils by GC/MS.
3. AOCS Official Method Cd 29b-13. Determination of 3-MCPD in fats and oils.
4. ISO 18363-1:2015. Animal and vegetable fats and oils — Determination of fatty-acid-bound chloropropanediols (MCPDs) and glycidol by GC/MS.