Improving the Sensitivity of Detection of 3-chloropropane-1,2-diol (3-MCPD) using Gas Chromatography with Negative Chemical Ionisation Mass Spectrometry detection

Significance of the Topic

3-Chloropropane-1,2-diol (3-MCPD) is a recognized toxic contaminant that forms during acid hydrolysis of vegetable proteins used in products like soy sauce. It exhibits carcinogenic potential in animal studies and poses risks to human health. Regulatory bodies such as the European Commission have set limits (0.02 mg/kg on dry matter) to control its presence in food. Accurate and sensitive analytical methods are therefore essential to monitor and minimize dietary exposure to 3-MCPD.

Objectives and Study Overview

The study aimed to enhance detection sensitivity for 3-MCPD by employing gas chromatography coupled with negative chemical ionisation mass spectrometry (GC-NCI-MS). The performance of GC-NCI-MS was compared with traditional electron impact MS (EI-MS) in both scan and selected ion monitoring (SIM) modes. Calibration, limits of detection, quantitation, and method applicability to soy sauce samples were evaluated.

Methodology and Instrumentation

The analytical procedure involved:

• Sample Preparation: Spiking soy sauce with internal standard (3-MCPD-d5), salt addition, sonication, and solid phase extraction using Extrelut 20 columns.
• Derivatisation: Reaction of 3-MCPD with N-heptafluorobutyrylimidazole (HFBI) at 70°C for 20 minutes to form a perfluoroalkylated derivative.
• Chromatographic Separation: DB-5 capillary column, helium carrier gas, splitless injection, and a temperature program from 50°C to 270°C.

Used Instrumentation

• Shimadzu GCMS-QP5050A gas chromatograph mass spectrometer
• Shimadzu AOC-20i/s autosampler
• GCMSsolution data analysis software

Key Results and Discussion

• EI-MS in SIM mode achieved a detection limit of approximately 2 ng/mL using m/z 253.
• NCI-MS in scan mode provided limits of 0.25 to 1 ng/mL (m/z 213 and 347), with some matrix overlap at m/z 213.
• NCI-MS in SIM mode further improved sensitivity to about 0.1 ng/mL using m/z 446 for 3-MCPD and m/z 507 for the deuterated standard.
• Calibration curves exhibited excellent linearity (r2 > 0.9999) over ranges from 2 to 15,000 ng/mL.
• Spiked soy sauce samples at 10 ppb showed recoveries between 135% and 150%, confirming method suitability for complex matrices.

Benefits and Practical Applications

This GC-NCI-MS approach delivers superior sensitivity and selectivity for trace-level analysis of 3-MCPD in food products. It enables reliable quantitation at regulatory limits and supports quality assurance, compliance testing, and safety monitoring in the food industry.

Future Trends and Opportunities

• Development of automated high-throughput workflows combining solid-phase extraction and GC-NCI-MS.
• Integration with laboratory information management systems (LIMS) for enhanced data traceability.
• Exploration of alternative derivatisation reagents for improved reaction kinetics.
• Expansion to other chloropropanol contaminants and analogues in diverse food matrices.
• Miniaturized and portable GC-NCI-MS platforms for on-site screening.

Conclusion

The application of negative chemical ionisation mass spectrometry significantly improves detection and quantitation of 3-MCPD compared to conventional EI-MS. With low detection limits, robust linearity, and effective performance in real samples, GC-NCI-MS represents a powerful tool for regulatory compliance and food safety assurance.

References

• Brereton P, Kelly J, Crews C, Honour S, Wood R, Davies A. Collaborative study on 3-chloropropanediol determination by GC-MS. J AOAC Int. 2001;84(2):455–465.
• Collier PD, van Bergen CA, Cromie DDO, et al. Mechanism of chloropropanol formation in protein hydrolysates. J Am Oil Chem Soc. 1991;68:785–790.
• Lynch BS, Bryant DW, Hook GJ, Nestmann ER, Munro IC. Toxicology of 3-MCPD. Int J Toxicol. 1998;17:47–76.