Analysis of 3-chloro-1,2-propanediol in soy sauce (hydrolysed vegetable protein – HVP)

Importance of the Topic

Acid-hydrolysed vegetable proteins such as soy sauce can contain 3-chloro-1,2-propanediol, a genotoxic compound that has prompted strict regulatory limits. Analytical methods with high sensitivity and specificity are essential to ensure food safety and compliance.

Study Objectives and Overview

This application report describes the development of a sensitive GC–MS method using HFBI derivatization to quantify trace levels of 3-MCPD in soy sauce HVP. The aim was to achieve detection below the European limit of 0.02 mg/kg (40 % dry matter basis).

Methodology

Sample Preparation:

• Weigh 8 g of soy sauce and adjust to 20 g with 5 M NaCl, homogenize by sonication.
• Load onto Extrelut NT 20 and elute non-polar matrix components with hexane–diethyl ether (90:10).
• Recover 3-MCPD with diethyl ether and concentrate by rotary evaporation at 35 °C.
• Dry 2 mL of extract, reconstitute in 1 mL of 2,2,4-trimethylpentane.

Derivatization and Analysis:

• Derivatize with N-(heptafluorobutyryl)imidazole.
• Inject 1 µL splitless into the Shimadzu QP5050A GC–MS operated in Selected Ion Monitoring.

Used Instrumentation

• Shimadzu QP5050A GC–MS with GCMSsolution workstation.
• DB-5ms column (30 m × 0.25 mm × 0.25 µm).
• Carrier gas: helium at 100 kPa.
• Injector and interface temperatures: 270 °C; oven program: 50 °C (1 min) → 90 °C at 2 °C/min → 270 °C at 40 °C/min.
• SIM ions monitored: m/z 253, 275, 289, 291, 453.

Key Results and Discussion

External calibration over 0.005–15 µg/mL yielded r = 0.9999. The method achieved a detection limit of 0.002 µg/mL (equivalent to 0.01 mg/kg in soy sauce), outperforming GC/ECD methods. A clear HFBI-derivative peak at 10.96 min was confirmed by library match (similarity index = 87). The approach demonstrates excellent selectivity and reproducibility for 3-MCPD quantitation.

Benefits and Practical Applications

This validated method provides reliable monitoring of 3-MCPD at sub-regulatory levels, supporting routine QA/QC in food and ingredient manufacturers. Its sensitivity and specificity make it suitable for compliance testing and risk assessment of acid-hydrolysed proteins.

Future Trends and Opportunities

Potential developments include accelerated derivatization protocols, automated sample cleanup workflows, integration with high-resolution MS for multi-residue analysis, and expansion of spectral libraries to cover emerging chloropropanol contaminants.

Conclusion

The HFBI-derivatization GC–MS method on the Shimadzu QP5050A delivers low detection limits and robust quantitation of 3-MCPD in soy sauce, meeting regulatory requirements and reinforcing food safety controls.

References

1. Velisek et al., J. Agric. Food Chem., 28 (1980) 1142–1144.
2. Food Surveillance Information Sheet No. 14/01, Food Standards Agency, UK.
3. P.D. Collier et al., J. Chromatogr., 589 (1992) 109–119.
4. Brereton et al., J. AOAC Int., 84 (2001) 455–465.