Parallel detection in a single ICR cell: Spectral averaging and improved S/N without increased acquisition time

Abstract

Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is well-renowned for its ultrahigh resolving power and mass measurement accuracy. As with other types of analytical instrumentation, achievable signal-to-noise ratio (S/N) is an important analytical figure of merit with FTICR-MS. S/N can be improved with higher magnetic fields and longer time-domain signal acquisition periods. However, serial signal averaging of spectra or time-domain signals acquired with multiple ion populations is most commonly used to improve S/N. On the other hand, serial acquisition and averaging of multiple scans significantly increases required data acquisition time and is often incompatible with on-line chromatographic separations. In this study, we investigated the potential for increased S/N by averaging 4 spectra that were acquired in parallel with a single ICR cell with 4 pairs of dipole detection electrodes, each with an independent pre-amplifier. This spectral averaging was achieved with no need for multiple ion accumulation events nor multiple, serial excitation and detection events. These efforts demonstrated that parallel signal acquisition with 4 detector electrode pairs produces S/N 1.76-fold higher than that from a single detection electrode pair. With parallel detection, improved S/N was achieved with no observable loss in resolving power (100,000) as compared with that from a single detection electrode pair. These results demonstrate that parallel detection of multiple induced image current signals with multiple preamplifiers exists as a viable option for future instrumentation to increase achievable S/N and sensitivity. This approach may have general utility especially where conventional serial signal averaging is impractical.