Single-run separation of cationic, anionic, and polyanionic compounds by CE-ESI-MS.

Area of Science:

• Analytical Chemistry
• Separation Science
• Mass Spectrometry

Background:

• Coupling capillary electrophoresis (CE) to electrospray ionization mass spectrometry (ESI-MS) is challenging due to maintaining electrical contact.
• Separating polyanionic compounds with high electrophoretic mobility is incompatible with standard CE-ESI-MS setups using bare fused-silica capillaries under negative polarity.

Purpose of the Study:

• To develop a single-run method for separating cationic, anionic, and polyanionic compounds using CE-ESI-MS.
• To overcome the technical difficulties associated with CE-ESI-MS coupling for challenging analyte types.

Main Methods:

• Evaluation of alternative approaches for CE-ESI-MS coupling.
• Application to the separation of cationic and polyanionic compounds, specifically synthesis intermediates of medical imaging contrast agents.
• Utilizing neutrally coated polymethylsiloxane (DB-1) capillaries with negative voltage and compensating pressure.
• Dynamically modifying bare fused-silica capillary inner walls with a polycationic polymer (hexadimethrine bromide) under negative voltage.

Main Results:

• Successful single-run separation and detection of both cationic and anionic compounds were achieved.
• Two distinct methods were validated for overcoming the electrical contact issue in CE-ESI-MS.
• The developed methods are applicable to complex mixtures including synthesis intermediates for medical imaging agents.

Conclusions:

• A robust CE-ESI-MS method enables simultaneous separation of diverse charged compounds in a single run.
• The study provides effective strategies for managing electroosmotic flow and maintaining electrical continuity in CE-ESI-MS.
• This advancement facilitates the analysis of complex chemical mixtures relevant to pharmaceutical and medical imaging development.