Redox buffering in an electrospray ion source using a copper capillary emitter

Area of Science:

• Analytical Chemistry
• Electrochemistry

Background:

• Electrospray ionization (ESI) mass spectrometry relies on electrochemical reactions at the emitter electrode for ion production.
• Conventional stainless-steel emitters can lead to uncontrolled analyte oxidation or reduction.

Purpose of the Study:

• To investigate the use of a copper capillary emitter as a redox buffer in positive ion mode electrospray mass spectrometry.
• To demonstrate improved control over electrochemical reactions at the emitter electrode.

Main Methods:

• Utilized a copper capillary emitter in a two-electrode, controlled-current electrochemical flow cell for electrospray mass spectrometry.
• Compared the electrochemical behavior of the copper emitter with a standard stainless-steel emitter using N-phenyl-1,4-phenylenediamine.

Main Results:

• The copper capillary emitter maintained a stable interfacial potential near the copper corrosion equilibrium potential, acting as a redox buffer.
• Oxidation of N-phenyl-1,4-phenylenediamine was completely avoided with the copper emitter, unlike with stainless-steel emitters.
• Demonstrated that reduction reactions can occur at the copper emitter in positive ion mode.

Conclusions:

• Copper capillary emitters offer superior control over electrochemical reactions in electrospray mass spectrometry by acting as redox buffers.
• This approach prevents unwanted analyte transformations and facilitates the introduction of metal ions for analytical applications.