Parts per million mass accuracy on an Orbitrap mass spectrometer via lock mass injection into a C-trap

TY - JOUR

T1 - Parts per million mass accuracy on an Orbitrap mass spectrometer via lock mass injection into a C-trap

AU - Olsen, Jesper Velgaard

AU - de Godoy, Lyris M F

AU - Li, Guoqing

AU - Macek, Boris

AU - Mortensen, Peter

AU - Pesch, Reinhold

AU - Makarov, Alexander

AU - Lange, Oliver

AU - Horning, Stevan

AU - Mann, Matthias

N1 - Keywords: Freeze Drying; Mass Spectrometry; Peptide Fragments; Reproducibility of Results; Sensitivity and Specificity; Serum Albumin, Bovine

PY - 2005

Y1 - 2005

N2 - Mass accuracy is a key parameter of mass spectrometric performance. TOF instruments can reach low parts per million, and FT-ICR instruments are capable of even greater accuracy provided ion numbers are well controlled. Here we demonstrate sub-ppm mass accuracy on a linear ion trap coupled via a radio frequency-only storage trap (C-trap) to the orbitrap mass spectrometer (LTQ Orbitrap). Prior to acquisition of a spectrum, a background ion originating from ambient air is first transferred to the C-trap. Ions forming the MS or MS(n) spectrum are then added to this species, and all ions are injected into the orbitrap for analysis. Real time recalibration on the "lock mass" by corrections of mass shift removes mass error associated with calibration of the mass scale. The remaining mass error is mainly due to imperfect peaks caused by weak signals and is addressed by averaging the mass measurement over the LC peak, weighted by signal intensity. For peptide database searches in proteomics, we introduce a variable mass tolerance and achieve average absolute mass deviations of 0.48 ppm (standard deviation 0.38 ppm) and maximal deviations of less than 2 ppm. For tandem mass spectra we demonstrate similarly high mass accuracy and discuss its impact on database searching. High and routine mass accuracy in a compact instrument will dramatically improve certainty of peptide and small molecule identification.

AB - Mass accuracy is a key parameter of mass spectrometric performance. TOF instruments can reach low parts per million, and FT-ICR instruments are capable of even greater accuracy provided ion numbers are well controlled. Here we demonstrate sub-ppm mass accuracy on a linear ion trap coupled via a radio frequency-only storage trap (C-trap) to the orbitrap mass spectrometer (LTQ Orbitrap). Prior to acquisition of a spectrum, a background ion originating from ambient air is first transferred to the C-trap. Ions forming the MS or MS(n) spectrum are then added to this species, and all ions are injected into the orbitrap for analysis. Real time recalibration on the "lock mass" by corrections of mass shift removes mass error associated with calibration of the mass scale. The remaining mass error is mainly due to imperfect peaks caused by weak signals and is addressed by averaging the mass measurement over the LC peak, weighted by signal intensity. For peptide database searches in proteomics, we introduce a variable mass tolerance and achieve average absolute mass deviations of 0.48 ppm (standard deviation 0.38 ppm) and maximal deviations of less than 2 ppm. For tandem mass spectra we demonstrate similarly high mass accuracy and discuss its impact on database searching. High and routine mass accuracy in a compact instrument will dramatically improve certainty of peptide and small molecule identification.

U2 - 10.1074/mcp.T500030-MCP200

DO - 10.1074/mcp.T500030-MCP200

M3 - Journal article

C2 - 16249172

SN - 1535-9476

VL - 4

SP - 2010

EP - 2021

JO - Molecular and Cellular Proteomics

JF - Molecular and Cellular Proteomics

IS - 12

ER -