Quantifying Sphingomyelin in Dairy through Infusion-Based Shotgun Mass Spectrometry with Lithium-Ion-Induced...

Area of Science:

• Lipidomics
• Mass Spectrometry
• Analytical Chemistry

Background:

• Quantifying sphingomyelin (SM) species using mass spectrometry (MS) is challenging due to interference from isobaric phosphatidylcholine (PC) species.
• Both SM and PC species produce a common m/z 184 product ion, complicating accurate measurements.

Purpose of the Study:

• To develop a selective and accurate method for quantifying individual sphingomyelin (SM) species in complex lipid matrices.
• To overcome the analytical interference from phosphatidylcholine (PC) species during SM quantification by mass spectrometry.

Main Methods:

• Utilized lithium ion adducts of SM, which undergo selective dehydration with a neutral loss of -207 Da.
• Developed a SM-selective method using MS3 for identifying target species and employed multiple reaction monitoring (MRM) for quantification.
• Characterized sphingosine base and acyl chain composition using SM-selective fragments in MS3.

Main Results:

• Identified 50 individual SM species in bovine milk, with varying sphingosine bases and acyl fatty acids.
• Achieved high recovery (99.7%) for spiked SM standards and low variability (<10% CV) for endogenous SM.
• Established sensitive limits of detection (1.4-5.55 nM) and quantitation (11.8-178.1 nM).

Conclusions:

• The developed MS-MRM method provides accurate and precise quantification of SM species in dairy products.
• This method is applicable to various dairy matrices, including whole milk, half-and-half, whipping cream, and goat milk.
• The technique offers a robust solution for analyzing complex lipid profiles in food science and nutrition research.