An interface with a linear quadrupole ion guide for an electrospray-ion trap mass spectrometer system

Area of Science:

• Analytical Chemistry
• Mass Spectrometry Instrumentation

Background:

• Electrospray ionization (ESI) 3D ion trap mass spectrometry (MS) systems face challenges with duty cycle and matrix interference.
• Space charge effects from excess matrix ions can degrade performance in 3D ion traps.

Purpose of the Study:

• To introduce a new ion sampling interface for ESI 3D ion trap MS.
• To enhance system performance, specifically duty cycle and sensitivity, by utilizing linear radiofrequency (RF) quadrupoles.

Main Methods:

• Incorporation of linear RF quadrupoles as ion guides and traps within the ESI-MS system.
• Demonstration of ion trapping in linear quadrupoles to improve duty cycle.
• Utilizing dipolar excitation for ion ejection from linear quadrupoles.
• Employing a composite waveform with frequency notch for selective matrix ion ejection.
• Analyzing trace reserpine in a poly(propylene glycol) matrix.

Main Results:

• Achieved ion ejection resolution up to 254 for protonated reserpine ions (m/z 609.3).
• Successfully isolated trace analyte ions by ejecting matrix ions in a linear quadrupole.
• Demonstrated a dramatic increase in resolution and sensitivity for trace reserpine detection.
• Achieved a 5-fold increase in sensitivity and a 7-fold reduction in acquisition time compared to in-trap matrix ion ejection.

Conclusions:

• The new ion sampling interface effectively enhances ESI 3D ion trap MS performance.
• Linear quadrupole ion trapping and selective ion ejection are crucial for overcoming matrix effects and space charge issues.
• This approach significantly improves sensitivity and efficiency for analyzing trace analytes in complex samples.