Optimal pressure conditions for unbiased external ion accumulation in a two-dimensional radio-frequency quadrupole for Fourier transform ion cyclotron resonance mass spectrometry.
When combined with on-line separations (e.g., capillary liquid chromatography (LC)), Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) provides a powerful tool for biological applications, and particularly proteomic studies. The sensitivity, dynamic range, and duty cycle provided by FTICR-MS have been shown to be increased by ion trapping and accumulation in a two-dimensional (2D) radio-frequency (rf)-only multipole positioned externally to an FTICR cell. However, it is important that ions be detected across the desired m/z range without a significant bias. In this work we found that pressure inside the accumulation rf-quadrupole plays an important role in obtaining "unbiased" ion accumulation. Pressure optimization was performed in both pulsed and continuous modes. It was found that unbiased accumulation in a 2D rf-only quadrupole could be achieved in the pressure range of 5 x 10(-4) to 5 x 10(-3) Torr. External ion accumulation performed at the optimal pressure resulted in an increase in both the spectrum acquisition rates and dynamic range.
Belov
M E
ME
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
Gorshkov
M V
MV
Alving
K
K
Smith
R D
RD
D000465:Algorithms; D017357:Cyclotrons; D005583:Fourier Analysis; D013058:Mass Spectrometry / Q000379:methods*; D008970:Molecular Weight; D010455:Peptides / Q000737:chemistry
D010455:Peptides