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

Methodology for performing precursor and neutral loss scans in an RF scanning linear quadrupole ion trap is described and compared to the unconventional ac frequency scan technique. In the RF scanning variant, precursor ions are mass selectively excited by a fixed frequency resonance excitation sign...

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Bibliographic Details
Published in:Journal of the American Society for Mass Spectrometry 2018-07, Vol.29 (7), p.1345-1354
Main Authors: Snyder, Dalton T., Szalwinski, Lucas J., Schrader, Robert L., Pirro, Valentina, Hilger, Ryan, Cooks, R. Graham
Format: Article
Language:English
Subjects:
Analytical Chemistry
Bioinformatics
Biotechnology
Chemical warfare
CHEMICAL WARFARE AGENTS
Chemistry
Chemistry and Materials Science
COMPARATIVE EVALUATIONS
Ejection
EXCITATION
INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
IONIZATION
IONS
MASS
Mass spectrometry
NONLINEAR PROBLEMS
Organic Chemistry
Permutations
PLASMA
Precursors
Proteomics
QUADRUPOLES
Radio frequency
RADIOWAVE RADIATION
Research Article
RESONANCE
Scanning
TRAPS
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Summary:Methodology for performing precursor and neutral loss scans in an RF scanning linear quadrupole ion trap is described and compared to the unconventional ac frequency scan technique. In the RF scanning variant, precursor ions are mass selectively excited by a fixed frequency resonance excitation signal at low Mathieu q while the RF amplitude is ramped linearly to pass ions through the point of excitation such that the excited ion’s m/z varies linearly with time. Ironically, a nonlinear ac frequency scan is still required for ejection of the product ions since their frequencies vary nonlinearly with the linearly varying RF amplitude. In the case of the precursor scan, the ejection frequency must be scanned so that it is fixed on a product ion m/z throughout the RF scan, whereas in the neutral loss scan, it must be scanned to maintain a constant mass offset from the excited precursor ions. Both simultaneous and sequential permutation scans are possible; only the former are demonstrated here. The scans described are performed on a variety of samples using different ionization sources: protonated amphetamine ions generated by nanoelectrospray ionization (nESI), explosives ionized by low-temperature plasma (LTP), and chemical warfare agent simulants sampled from a surface and analyzed with swab touch spray (TS). We lastly conclude that the ac frequency scan variant of these MS/MS scans is preferred due to electronic simplicity. In an accompanying manuscript, we thus describe the implementation of orthogonal double resonance precursor and neutral loss scans on the Mini 12 using constant RF voltage. Graphical Abstract ᅟ
ISSN:1044-0305
1879-1123
DOI:10.1007/s13361-018-1920-3