Rapid analysis of triglycerides and fatty acids in food oils using DART-MS with high-speed polarity switching

Significance of the Topic

Direct analysis of triglycerides and fatty acids in edible oils is vital for quality control, authentication and nutritional assessment. Conventional gas or liquid chromatography often demands extensive sample preparation, long analysis times and suffers from memory effects. Rapid, high-throughput methods improve laboratory efficiency in food analysis.

Objectives and Study Overview

This study explores the application of ambient ionization mass spectrometry, specifically Direct Analysis in Real Time (DART) coupled to a triple quadrupole mass spectrometer with ultra-fast polarity switching. The goal is to achieve simultaneous positive and negative ion analyses for profiling triglycerides and free fatty acids in edible oils within a single rapid run.

Methodology and Instrumentation

• Sample types: Commercial edible oils (olive, sesame seed, Chinese chili oil).
• Ionization: DART-OS ion source with helium gas flow and heater temperatures varied (300°C, 400°C, 500°C).
• Mass spectrometer: Shimadzu LCMS-8030/8040 with Q3 scan range m/z 50–1200 and ultra-fast polarity switching (15 ms), achieving two full scans per second.
• Data acquisition: Simultaneous positive and negative mode spectra to capture protonated/ammoniated glycerides and deprotonated fatty acids.

Main Results and Discussion

• Optimal Conditions: A heater temperature of 500°C provided enhanced signals for triglycerides in positive mode while retaining clear fatty acid signals in negative mode.
• Chinese Chili Oil: Positive spectra revealed triglyceride species comprising various combinations of oleic, linoleic and palmitic acids as [M+NH4]+ and [M+H]+ adducts. Negative spectra detected linoleic (m/z 279) and oleic (m/z 281) acids consistently.
• Olive and Sesame Oils: Distinct fatty acid profiles were observed. Olive oil showed higher oleic acid relative intensity; sesame oil displayed a balanced oleic/linoleic ratio. Corresponding triglyceride clusters in the positive mode matched these fatty acid distributions.
• Correlation: A strong concordance between triglyceride composition (positive mode) and free fatty acid abundance ratios (negative mode) was established within a single DART-MS experiment.

Benefits and Practical Applications

Rapid, minimal-prep analysis reduces sample handling and memory effects. The high-throughput capability suits quality control, adulteration detection and routine screening of edible oil authenticity and nutritional content in food industry and regulatory labs.

Future Trends and Potential Applications

• Extension to other lipid classes and complex food matrices.
• Integration with chemometric models for automated classification of oil varieties.
• Development of portable DART-MS platforms for on-site quality assessment.

Conclusion

Ultra-fast polarity switching in DART-MS enables simultaneous profiling of triglycerides and free fatty acids in edible oils with high speed and reliability. This approach streamlines lipid analysis workflows and provides comprehensive compositional information in a single analysis.

Reference

Rapid analysis of triglycerides and fatty acids in food oils using DART-MS with high-speed polarity switching, Shun Wada et al., Shimadzu Application Note PO-CON1310E, ASMS 2013.