Detection of Large Ions in Time-of-Flight Mass Spectrometry: Effects of Ion Mass and Acceleration Voltage on Microchannel Plate Detector Response

Detection of Large Ions in Time-of-Flight Mass Spectrometry: Effects of Ion Mass and Acceleration Voltage on Microchannel Plate Detector Response

Citation

Liu, R., Li, Q., & Smith, L. M. (2014). Detection of large ions in time-of-flight mass spectrometry: Effects of ion mass and acceleration voltage on microchannel plate detector response. Journal of the American Society for Mass Spectrometry, 25(8), 1374–1383. 

Keywords

  • Time-of-flight mass spectrometry (TOF-MS)
  • Microchannel plate (MCP) detector
  • Ion detection
  • Secondary electron yield
  • Detection efficiency
  • Acceleration voltage
  • Ion mass
  • Peptide
  • Protein
  • Inductive charge detector (ICD)

Brief

The efficiency of microchannel plate (MCP) detectors in detecting ions in time-of-flight mass spectrometry is very close to unity for smaller ions at high acceleration voltages but decreases substantially for larger proteins, particularly at low acceleration voltages. One of the significant challenges in biological mass spectrometry is the development of new approaches to analyzing complex proteoform mixtures. Protein ions are generally produced for mass spectrometry analysis by electrospray ionization as highly charged ions or by matrix-assisted laser desorption/ionization as singly charged ions. The efficiency of secondary electron generation in MCP detectors has a strong dependence on ion mass and velocity. This study characterized the performance of these detectors to evaluate their merit relative to potential alternative detection modalities.

Summary

This article, published in 2014 in the J Am Soc Mass Spectrom, explores the effectiveness of microchannel plate (MCP) detectors in detecting large ions during time-of-flight mass spectrometry (TOF-MS). The authors, Ranran Liu, Qiyao Li, and Lloyd M. Smith, investigated how ion mass and acceleration voltage impact the detector's response They analyzed peptide/protein ions ranging from 1 kDa to 290 kDa and tested acceleration voltages between 5 kV and 25 kV.

A key finding was that MCP detectors are highly efficient in detecting smaller ions, especially at high acceleration voltages. For instance, angiotensin (1,046.5 Da) at 25 kV showed near-unity detection efficiency. However, larger proteins like immunoglobulin G (IgG) dimer (290 kDa), even at the highest acceleration voltage (25 kV), showed a decreased efficiency of approximately 11%.

The study highlights that while MCP detectors excel at detecting smaller peptides and proteins, their performance declines with larger proteins, particularly at low acceleration voltages.

Origin: https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC4108536&blobtype=pdf

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