Microchip electrospray performance during gradient elution with bulk conductivity changes.

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Separation Science

Background:

• Electrospray ionization mass spectrometry (ESI-MS) is crucial for analyzing complex mixtures.
• Spray mode instabilities in ESI-MS, particularly during reversed-phase HPLC, hinder data quality.
• The role of dynamic bulk conductivity changes in driving these instabilities remains unclear.

Purpose of the Study:

• To identify the primary cause of spray mode changes and instabilities in ESI-MS during HPLC.
• To investigate the influence of bulk conductivity on electrospray behavior.
• To establish a method for diagnosing electrospray modes and their onset potentials.

Main Methods:

• Modification of a microchip-HPLC/ESI-MS system for real-time electrospray diagnostics.
• Utilized frequency analysis of emitter current and spray imaging to characterize spray modes.
• Employed computational fluid dynamics (CFD) simulations with leaky dielectric fluid models.

Main Results:

• Identified dynamic bulk conductivity changes during gradient elution as the main driver of spray instabilities.
• Successfully detected distinct spray modes and their onset potentials using the developed diagnostic approach.
• CFD simulations confirmed the impact of conductivity and potential on cone-jet stability and morphology.

Conclusions:

• Bulk conductivity variations during reversed-phase HPLC are a critical factor affecting ESI-MS spray stability.
• The developed diagnostic method enables better understanding and control of electrospray behavior.
• This research provides insights for optimizing HPLC/ESI-MS methods for improved analytical performance.