Initial implementation of external accumulation liquid chromatography/electrospray ionization Fourier transform ion cyclotron resonance with automated gain control

Abstract

Capillary liquid chromatography (LC) separation coupled with external accumulation Fourier transform ion cyclotron resonance (FTICR) mass spectrometry has recently been demonstrated to have significant potential for proteomics research. Accumulation of an excessive space charge external to the FTICR cell ion trap has been shown to result in increased mass measurement error, undesirable ion discrimination and/or fragmentation, potentially causing misrepresentation or incorrect assignments of lower abundance peptides in the acquired mass spectra. In this work we report on the capability of data-dependent adjustment of ion accumulation times in the course of LC separations, further referred to as automated gain control (AGC). Three different AGC approaches were evaluated based on the number of putative peptides from a tryptic digest of four casein proteins detected in the course of LC/FTICR separations. When compared with the conventional technique, AGC was found to increase, up to a factor of 3, the total number of peptides identified.

Quantitative mass spectrometry in proteomics: a critical review

“…3c). In practice, saturation is more often observed for quadrupole TOF instruments than ion traps because these latter devices can control the number of ions before detection [70]. In any case, the relatively recent introduction of high-resolution/ high mass accuracy mass spectrometers in proteomics has interfering signals with signal to noise ratios too low for reliable quantification.…”

Advances in proteomics data analysis and display using an accurate mass and time tag approach

“…This capability for data-dependent adjustment of ion accumulation time during an LC separation maintains ion populations in the FTICR cell so as not to exceed a level that causes excessive space charge effects. AGC also helps eliminate m/z discrimination in the external ion trap and improves the MMA and/or the dynamic range of measurements (Belov, et al, 2003a, Belov, et al, 2003b. Recently, Thermo Electron Corporation has incorporated this AGC approach into their LTQ FT™ mass spectrometer.…”

Linear ion traps in mass spectrometry

“…For LC, mass spectrometry, Belov et al (2003) described a feedback mechanism that automatically adjusts the ion injection time to prevent space charge problems in the linear and FTMS traps. A pre-scan mass spectrum (similar to DREAMS) is obtained and based on the total ion signal chromatogram (the sum of the ion intensities for a range of m/z) the ion injection time is adjusted to allow similar numbers of charges to be accumulated in the linear trap.…”