Charge Retention/Charge Depletion in ESI-MS: Experimental Evidence

Area of Science:

• Analytical Chemistry
• Mass Spectrometry

Background:

• Chemical modifiers significantly impact ion signal distribution in mass spectrometry.
• Understanding these effects is crucial for accurate peptide analysis.

Purpose of the Study:

• To investigate the influence of liquid and gas phase additives on Substance P ion signal distribution.
• To elucidate the mechanisms behind charge depletion and retention.

Main Methods:

• Nanoelectrospray ionization mass spectrometry.
• Utilized polar protic and aprotic gas phase modifiers.
• Performed collision-induced dissociation experiments.

Main Results:

• Polar protic modifiers led to depletion of higher Substance P charge states ([SP+3H]³⁺) via cluster formation and deprotonation.
• Aprotic modifiers and supercharging agents promoted retention of higher charge states by stabilizing ions through clustering.
• Modifier accommodation into droplets delayed evaporation and ion release.

Conclusions:

• The properties of chemical modifiers dictate their interaction with peptide ions.
• Modifier-induced cluster formation and accommodation are key factors influencing ion charge state distribution.
• Tailoring modifier choice allows control over ion signal in mass spectrometry.