Identification of Double Bond Positions in Butter Triacylglycerols Using DPiMS QT Kit and OAD-TOF System

Significance of the Topic

Fats in food, predominantly present as triacylglycerols, play a critical role in nutrition and biological function. The location of double bonds in unsaturated fatty acids influences metabolic pathways and health outcomes. Rapid, accurate identification of these positional isomers is therefore essential for food science, clinical research, and quality control in the food industry.

Study Objectives and Overview

This application study aimed to demonstrate a direct, high-speed method for determining double bond positions in butter triacylglycerols. By integrating a direct probe ionization kit (DPiMS QT) with an oxygen attachment dissociation time-of-flight mass spectrometer (OAD-TOF, LCMS-9050), the workflow eliminates chromatographic separation while preserving structural detail of lipid isomers.

Methodology and Instrumentation

Sample preparation involved a simple extraction of 200 mg of butter with a water/isopropanol mixture, ultrasonication, centrifugation, and direct deposition of 10 µL on a liquid sample plate. The DPiMS QT probe enabled probe electrospray ionization with minimal contamination. The OAD-TOF system seamlessly switched between collision-induced dissociation (CID) and oxygen attachment dissociation (OAD) modes. Key analytical parameters included positive polarity, DL temperature 250 °C, heat block 50 °C, interface voltage 3.0 kV, collision energy 20 V (CID) and 5 V (OAD), and m/z range 100–1000. Total analysis time per sample was approximately 0.5 minutes.

Main Results and Discussion

MS1 spectra revealed around twenty triacylglycerol species ranging from C24:0 to C40:2. Data processing with MS-DIAL provided preliminary identification based on precursor m/z and sodium adducts. Selected targets TG 38:1 and TG 38:2 underwent MS/MS in CID mode to determine chain lengths and degrees of unsaturation. Subsequent OAD fragmentation produced position-specific neutral losses that pinpointed double bond locations at n-9 for 18:1 and at n-6 and n-9 for 18:2, resolving isomeric mixtures.

Benefits and Practical Applications

• Rapid screening: combined sample pretreatment and measurement within six minutes.
• Direct isomer discrimination: position-specific OAD fragmentation without derivatization.
• High mass accuracy: ensures confident annotation of double bond positions.

Future Trends and Potential Applications

Advances may include application to diverse lipid classes, integration with automated lipidomics platforms, quantitation of isomeric lipids in complex matrices, and direct tissue or in vivo analysis. Increased throughput and software-driven workflows will further expand the impact of direct probe OAD-TOF in nutritional, biomedical, and industrial research.

Conclusion

The combination of DPiMS QT direct probe ionization and OAD-TOF mass spectrometry offers a fast, reliable approach for structural elucidation of triacylglycerols in complex food matrices. It enables precise mapping of double bond positions without chromatography, supporting advanced lipidomics and quality control applications.

Used Instrumentation

• DPiMS QT probe electrospray ionization kit
• LCMS-9050 high-resolution quadrupole time-of-flight mass spectrometer
• OAD RADICAL SOURCE I for oxygen attachment dissociation

Reference

1. H. Uchino et al. Communications Chemistry 5, 162 (2022)
2. H. Tsugawa et al. Nature Methods 12, 523-526 (2015)