A LC-ESI-Q-TOF Method for Identification and Relative Composition Analysis of Triacylglycerols in Tropical Oil - (1) Coconut Oil

Importance of the Topic

Triacylglycerols (TAGs) are the primary lipid constituents in edible tropical oils such as coconut oil. Their detailed characterization is crucial for nutritional evaluation, quality control, and authenticity assessment in food and industrial applications. Direct identification of TAG molecular species bypasses labor-intensive hydrolysis and derivatization steps, enabling faster and more accurate profiling of lipid profiles.

Objectives and Study Overview

This study presents a rapid liquid chromatography–electrospray ionization–quadrupole time-of-flight mass spectrometry (LC-ESI-Q-TOF) method for direct identification and relative quantitation of TAGs in coconut oil. The aims were to:

• Develop a streamlined LC-ESI-Q-TOF workflow for comprehensive TAG identification without prior hydrolysis.
• Establish a data analysis protocol for unambiguous assignment of individual TAG species using high-resolution MS and MS/MS.
• Compare TAG profiles across multiple coconut oil brands to assess compositional consistency.

Methodology

Coconut oil samples from three brands were diluted in a chloroform-acetone (1:1) stock solution and further diluted in the mobile phase to 0.6 mg/mL for analysis. Chromatographic separation was achieved on a Shim-pack Velox C18 column (2.1×100 mm, 2.7 µm) using a 16 min gradient of 20 mM ammonium formate in water (A) and 80:20 2-propanol/acetonitrile (B) at 45°C and 0.4 mL/min flow rate.

Instrumentation Used

• LCMS-9030 Q-TOF with heated electrospray ionization (HESI) interface.
• Shim-pack Velox C18 column (2.1×100 mm, 2.7 µm).
• LabSolutions Insight Explore software for accurate mass and MS/MS data analysis.

Results and Discussion

The method identified 38 distinct TAGs, categorized by fatty acid saturation:

• Saturated TAGs (DB=0): Four major peaks with equivalent carbon numbers (ECN) 40–46 accounted for 62.5% of total peak area.
• Monounsaturated TAGs (DB=1): Nine species representing 35.2% of total TAGs.
• Polyunsaturated TAGs (DB>1): Ten minor components totaling 2.3%.

High-resolution precursor masses and MS/MS fragment ions corresponding to neutral losses of fatty acid residues enabled assignment of specific TAG structures (e.g., PLaLa, MMLa). Comparative profiling of three brands showed consistent distribution across saturation classes, with medium-chain saturated species being predominant.

Benefits and Practical Applications

• Significantly reduces sample preparation time by eliminating hydrolysis and derivatization.
• Provides both qualitative identification and relative quantitation in a single LC run.
• Facilitates routine quality control and authenticity testing in food, cosmetics, and pharmaceutical industries.

Future Trends and Potential Applications

Advancements in high-resolution LC-MS platforms and data analysis algorithms are expected to further enhance TAG speciation, including isomer differentiation. Integration with ion mobility spectrometry and database-driven spectral libraries could enable automated, high-throughput lipidomics workflows. Broader application to other edible and biodiesel feedstock oils will support comprehensive lipid profiling in food science and biofuel research.

Conclusion

The presented LC-ESI-Q-TOF method offers a robust, direct approach to identify and quantify TAG molecular species in coconut oil with high confidence. Its efficiency and accuracy make it suitable for diverse applications in analytical chemistry and quality assurance.

Reference

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