Gas phase reaction between chromones and solvent in an electrospray ionization source

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Organic Chemistry

Background:

• Chromones are a class of organic compounds with diverse biological activities.
• Electrospray ionization mass spectrometry (ESI-MS) is a common technique for analyzing chromones.
• Understanding ionization mechanisms is critical for accurate metabolite identification.

Purpose of the Study:

• To investigate the formation of unexpected ions observed during the ESI-MS analysis of chromones.
• To elucidate the underlying gas-phase reaction mechanisms responsible for these ions.
• To provide insights for accurate chromone and metabolite annotation in mass spectrometry.

Main Methods:

• Electrospray ionization mass spectrometry (ESI-MS) in negative ion mode.
• High-performance liquid chromatography-mass spectrometry (HPLC-MS).
• Deuterium labeling and collisional-induced dissociation (CID) experiments.

Main Results:

• Unexpected [M+17]− and [M+31]− ions were observed with high intensity in water and methanol solvents.
• The abundance of these adduct ions increased with electron-withdrawing substituents at the C-3 position of chromones.
• Mechanisms involving covalent gas-phase nucleophilic addition (with water) and noncovalent complex formation (with methanol) were proposed.

Conclusions:

• The formation of [M+17]− and [M+31]− ions is attributed to unique gas-phase reactions between chromones and solvent molecules.
• Recognizing these reactions is essential to prevent misannotation of chromones and their metabolites in mass spectrometry data.
• This study highlights the importance of considering solvent-mediated adduct formation in ESI-MS analysis.