文摘
A rectilinear ion trap (RIT) mass analyzer was incorporated into a mass spectrometer fitted with an electrosprayionization source and an atmospheric pressure interface.The RIT mass spectrometer, which was assembled in twodifferent configurations, was used for the study of biological compounds, for which performance data are given. Avariety of techniques, including the use of a balanced rf,elevated background gas pressure, automatic gain control,and resonance ejection waveforms with dynamically adjusted amplitude, were applied to enhance performance.The capabilities of the instrument were characterizedusing proteins, peptides, and pharmaceutical drugs. Unitresolution and an accuracy of better than m/z 0.2 wasachieved for mass-to-charge (m/z) ratios up to 2000 That a scan rate of ~3000 amu/(charge·s) while reducedscan rates gave greater resolution and peak widths of lessthan m/z 0.5 over the same range. The mass discrimination in trapping externally generated ions was characterized over the range m/z 190-2000 and an optimized lowmass cutoff value of m/z 120-140 was found to giveequal trapping efficiencies over the entire range. Theradial detection efficiency was measured as a function ofm/z ratio and found to rise from 35% at low m/z valuesto more than 90% for ions of m/z 1800. The way in whichthe ion trapping capacity depends on the dc trappingpotential was investigated by measuring the mass shift dueto space charge effects, and it was shown that low trappingpotentials minimize space charge effects by increasing theuseful volume of the device. The collision-induced dissociation (CID) capabilities of the RIT instrument wereevaluated by measuring isolation efficiency as a functionof mass resolution as well as measuring peptide CIDefficiencies. Overall CID efficiencies of more than 60%were easily reached, while isolation of an ion with unitresolution at m/z 524 was achieved with high rejection(>95%) of the adjacent ions. The overall analytical capabilities of the ESI-RIT instrument were demonstrated withthe analysis of a mixture of pharmaceutical compoundsusing multiple-stage mass spectrometry.
