# Electron Capture-Induced Charge Reduction Benefits the Recording of Ultralong Transients in Orbitrap-Based Individual-Ion Mass Spectrometry

## TL;DR

A new method using electron capture improves the detection of low-charge ions in mass spectrometry, enabling better analysis of small proteins.

## Contribution

Electron capture charge reduction (ECCR) is introduced to enhance ion stability in Orbitrap-based mass spectrometry.

## Key findings

- ECCR improves ion survival by up to 60-fold in long trapping experiments.
- ECCR enables detection of doubly charged ions from cytochrome c previously undetectable.
- Stability of ion trajectories is significantly improved with ECCR.

## Abstract

Recently, the use of ultralong transients has enabled
exceptional
resolution and sensitivity in Orbitrap-based charge detection mass
spectrometry (CDMS). Nevertheless, measuring small analytes carrying
a few charges remains a challenge. Prolonged trapping should, in theory,
allow for the detection of lower charged ions (<10+) due to enhanced
signal-to-noise (S/N) ratios. However,
in practice, due to ion decay through frequency drifts, or collision-induced
fragmentations, low m/z ions deviate
from the ideal coherent trajectories in the Orbitrap. Here, by incorporating
electron capture charge reduction (ECCR) in the gas phase prior to
CDMS, we show that charge reduction significantly improves the stability
of ion trajectories when ions are trapped for long periods in the
Orbitrap analyzer. Using proteins with molecular weights ranging from
12 to 900 kDa, we demonstrate that ECCR-CDMS enhances ion survival
by up to 60-fold, even enabling the detection of doubly charged individual
ions from cytochrome c that typically elude conventional Orbitrap-based
CDMS.