Structural resolution of disaccharides through halogen anion complexation using negative trapped ion mobility...

Area of Science:

• Analytical Chemistry
• Biochemistry
• Physical Chemistry

Background:

• Carbohydrates are crucial biomolecules, but their structural diversity poses challenges for analysis.
• Accurate carbohydrate structure determination is essential for understanding their biological functions.
• Ion mobility spectrometry (IMS) is an emerging technique for separating and analyzing ions.

Purpose of the Study:

• To investigate the utility of negative ion mode trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) for carbohydrate isomer differentiation.
• To compare the effectiveness of different halogen adducts (Cl, Br, I) in the negative ion mode for separating disaccharide isomers.
• To evaluate the potential of negative ion analysis as a complementary strategy to positive ion analysis for carbohydrate structure elucidation.

Main Methods:

• Analysis of eight disaccharides using TIMS-MS in negative ion mode with chloride, bromide, and iodide adducts ([M + X]^-).
• Comparison of collision cross section (CCS) differences between isomers in negative ion mode versus sodiated positive ion mode.
• Utilized density functional theory calculations to interpret observed conformers and ion-adduct interactions.

Main Results:

• Negative ion mode analysis, particularly with iodide adducts ([M + I]^-), demonstrated enhanced separation of disaccharide isomers.
• The [M + I]^- ion form achieved an average resolution (R_P-P) of 1.17, a 34.5% improvement over chloride adducts.
• Reversal of charge state in negative ion mode helped eliminate or reverse CCS differences between isomers.

Conclusions:

• Negative ion analysis, especially using iodide adducts, significantly improves the differentiation of carbohydrate isomers.
• This approach offers a powerful supplemental strategy to conventional positive ion analysis for complex carbohydrate separations.
• The findings highlight the potential of TIMS-MS in negative ion mode for detailed carbohydrate structure elucidation.