Analysis of Fatty Acids in Food Using PCIGC- MS/MS

Significance of the Topic

Fatty acids play critical roles in human nutrition and health management. N-3 polyunsaturated fatty acids like EPA and DHA confer cardiovascular benefits by reducing blood triglycerides, while excessive intake of saturated fats correlates with increased disease risk. Analytical methods capable of rapid, accurate, and sensitive quantification of a wide range of fatty acids are therefore essential in food science, nutrition research, and quality control.

Objectives and Study Overview

This study investigates the performance of four gas chromatography mass spectrometry modes in the batch analysis of fatty acids extracted from a fish matrix (saury). The modes compared include electron ionization selected ion monitoring (EI-SIM), positive chemical ionization selected ion monitoring (PCI-SIM), electron ionization multiple reaction monitoring (EI-MRM), and chemical ionization multiple reaction monitoring (PCI-MRM). The primary aims are to assess sensitivity and the ability to resolve target analytes from coeluting impurities.

Pretreatment Method

A standardized methylation protocol was applied using a commercial kit to convert fatty acids in 200 mg of pulverized saury flesh into their methyl esters. The procedure comprises solvent extraction, centrifugation, nitrogen drying, sequential reagent additions, and organic phase clean-up. Deionized water washes ensure removal of polar contaminants, yielding a purified test solution for GC-MS(/MS) analysis.

Instrumentation Used

• Shimadzu gas chromatograph mass spectrometer equipped with both electron ionization and positive chemical ionization sources
• GC-MS/MS capability for multiple reaction monitoring
• Analysis conditions and m/z monitoring parameters sourced from a validated GC/MS metabolite database

Main Results and Discussion

All four modes achieved separation of most fatty acid methyl esters from matrix interferences. However, notable differences emerged for highly unsaturated compounds such as methyl linolenate (18:3n-3) and methyl cis-11,14,17-icosatrienoate (20:3n-3). Under EI-SIM and EI-MRM, these analytes exhibited incomplete resolution due to multiple fragment ions and limited sensitivity. PCI-SIM provided improved sensitivity but relied on a single protonated molecular ion, complicating unambiguous peak identification. In contrast, PCI-MRM generated selective precursor–product ion transitions that eliminated nearby impurities, yielding clear chromatographic peaks and superior detection limits.

Benefits and Practical Applications

• PCI-MRM combines high sensitivity with robust mass selectivity, ideal for trace analysis in complex food matrices
• MRM workflows enable simultaneous quantification of multiple fatty acid species in a single batch run
• Improved peak identification reduces false positives and enhances reproducibility in quality control

Future Trends and Potential Applications

Advancements in ion source design and data acquisition speed will further enhance throughput and sensitivity in fatty acid profiling. Integration with high-resolution mass analyzers and software-based deconvolution will enable detailed isomeric differentiation. Applications may extend to clinical lipidomics, environmental monitoring of lipid biomarkers, and real-time process control in food manufacturing.

Conclusion

The PCI-MRM approach emerges as the most effective mode for multi-component fatty acid analysis in complex food samples, offering both high sensitivity and precise mass-based separation. Its adoption can streamline nutritional studies and quality assurance workflows.

Reference

No formal references provided