Collision Cross Section (CCS) Database: An Additional Measure to Characterize Steroids

Area of Science:

• Analytical Chemistry
• Biochemistry
• Mass Spectrometry

Background:

• Liquid chromatography-mass spectrometry (LC-MS) is crucial for steroid profiling.
• Existing methods face challenges in differentiating structurally similar steroids and metabolites.
• Ion mobility spectrometry (IMS) offers an additional separation dimension, collision cross section (CCS).

Purpose of the Study:

• To develop the first extensive collision cross section (CCS) database for steroid analysis.
• To evaluate the utility of CCS in enhancing steroid profiling workflows.
• To provide a publicly available resource for steroid identification and quantification.

Main Methods:

• Generated a CCS database for 300 steroids, including endogenous and synthetic compounds.
• Measured CCS values using nitrogen as drift gas in an ion mobility cell.
• Analyzed ionized species in positive and negative electrospray ionization modes.

Main Results:

• The database comprises 1080 ions covering 127 androgens, 84 estrogens, 50 corticosteroids, and 39 progestagens.
• CCS values provide additional information beyond mass-to-charge ratio and retention time, aiding identification of unusual steroid structures (e.g., glucuronides, esters).
• Separation of isomeric steroid pairs was achieved based on CCS differences, demonstrating enhanced selectivity.

Conclusions:

• Incorporating CCS into analytical workflows significantly increases selectivity and confidence in steroid analysis.
• The developed CCS database is a valuable resource for improving steroid identification and quantification.
• The study establishes quality criteria and an interlaboratory reproducibility approach for CCS measurements.