Ambient Pressure Ion Funnel: Concepts, Simulations, and Analytical Performance

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Ion Optics

Background:

• Ion transmission from atmospheric pressure to vacuum in mass spectrometry (MS) leads to significant ion loss, limiting instrument performance.
• Electrospray ionization (ESI) is a common atmospheric pressure ionization technique, but ion transfer inefficiencies remain a challenge.

Purpose of the Study:

• To introduce and evaluate an ambient pressure ion funnel (APIF) for enhancing ion focusing and transmission in ESI-MS.
• To investigate the impact of APIF on ion abundance, sensitivity, and detection limits for various ions.

Main Methods:

• Implementation of an ambient pressure ion funnel (APIF) operating at approximately 777 Torr.
• Testing the APIF with seven singly charged ions across a range of mass-to-charge ratios (m/z 124-1131).
• Utilizing simulated ion trajectories to understand the underlying principles of APIF performance.

Main Results:

• The APIF significantly improved ion abundances (up to ~17-fold), sensitivity (up to ~16-fold), and detection limits (up to ~3-fold) compared to conventional ESI-MS.
• Simulations indicated that high RF field amplitude, a strong DC field, and a wide exit electrode contribute to effective radial ion confinement and focusing.
• Observed performance enhancements were consistent across tested singly charged ions.

Conclusions:

• The ambient pressure ion funnel (APIF) effectively focuses ions at atmospheric pressure, overcoming traditional ion transmission losses in ESI-MS.
• APIF technology offers a promising solution for improving performance in ESI-MS and related atmospheric pressure ionization techniques.
• Future applications include enhancing ion mobility spectrometry and high flow rate liquid chromatography-mass spectrometry platforms.