A Personal Perspective on the Evolution of Today's LC/MS Techniques

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Chromatography

Background:

• Early liquid chromatography-mass spectrometry (LC/MS) faced challenges coupling high-flow liquid chromatography (HPLC) effluent into vacuum mass spectrometers.
• Initial LC/MS interfaces utilized vacuum-based ion sources like electron ionization (EI) and chemical ionization (CI), limiting analytical success.
• John Fenn's work on nano-flow electrospray ionization (ESI) with atmospheric pressure ionization (API) mass spectrometry offered a breakthrough.

Purpose of the Study:

• To describe the personal development and evolution of atmospheric pressure ionization (API) techniques for liquid chromatography-mass spectrometry (LC/MS).
• To address the limitations of early electrospray ionization (ESI) in handling high mobile phase flow rates common in HPLC.
• To introduce the development of pneumatically assisted electrospray, termed 'Ion Spray', to enhance ESI performance.

Main Methods:

• Review of historical development of atmospheric pressure ionization (API) LC/MS techniques.
• Description of early LC/MS interfaces and their limitations.
• Development and implementation of a coaxial nitrogen gas flow to assist electrospray at higher liquid flow rates.

Main Results:

• Atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) emerged as key API techniques.
• A significant challenge was integrating HPLC effluent with vacuum mass spectrometers.
• Pneumatically assisted electrospray (Ion Spray) was developed to enable ESI at higher flow rates, overcoming previous limitations.

Conclusions:

• The development of pneumatically assisted electrospray (Ion Spray) was crucial for advancing API LC/MS capabilities.
• This technique, initially termed 'Ion Spray', is now widely known as 'electrospray' and is a standard in modern LC/MS.
• The personal perspective highlights key innovations in mass spectrometry interface development.