Precursor and Neutral Loss Scans in an RF Scanning Linear Quadrupole Ion Trap

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Ion Trap Technology

Background:

• Linear quadrupole ion traps are crucial for mass spectrometry/mass spectrometry (MS/MS) analyses.
• Precursor and neutral loss scans are vital MS/MS techniques for structural elucidation and compound identification.

Purpose of the Study:

• To describe and compare a novel RF scanning methodology for precursor and neutral loss scans in linear quadrupole ion traps.
• To evaluate the electronic simplicity and applicability of the RF scanning technique against the conventional ac frequency scan.

Main Methods:

• Development and implementation of an RF scanning technique for precursor and neutral loss scans.
• Mass selective excitation of precursor ions with a fixed frequency resonance excitation signal and linearly ramped RF amplitude.
• Nonlinear ac frequency scan for product ion ejection, adapted for both precursor and neutral loss scan requirements.
• Demonstration using various ionization sources including nanoelectrospray ionization (nESI), low-temperature plasma (LTP), and swab touch spray (TS).

Main Results:

• The RF scanning method allows for linear variation of precursor ion m/z with time.
• Both simultaneous and sequential permutation scans were demonstrated.
• Successful application of the technique to diverse samples like amphetamine, explosives, and chemical warfare agent simulants.
• The ac frequency scan variant of these MS/MS scans is preferred due to electronic simplicity.

Conclusions:

• The RF scanning methodology provides a viable alternative for precursor and neutral loss scans in linear quadrupole ion traps.
• The ac frequency scan variant offers advantages in electronic simplicity for MS/MS experiments.
• Further implementation of orthogonal double resonance scans using constant RF voltage is described in an accompanying manuscript.