17th International Mass Spectrometry Conference :: Prague, 2006
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|Presentation date:||Wed, Aug 30, 2006|
|Presentation time:||12:10 – 12:30|
Anatoli Verentchikov1, Yuri Hasin1, Mikhail Gavrik1, Boris Kozlov1, Marat Muradumov1, Mikhail Yavor1, Vyatcheslav Artaev21 Institute for Analytical Instrumentation of the Russian Academy of Science, St. Petersburg, Russian Federation
Correspondence address: Anatoli Verentchikov, Institute for Analytical Instrumentation of the Russian Academy of Science, 26 Rizhsky ave, St. Petersburg, 198103 Russian Federation.
Keywords: Digests, Tryptic; Mass Resolution; Mass Spectrometry, Time of Flight; Mixture Analysis.
Novel aspect: Developed novel type - planar multireflecting TOF MS for continous ion sources. Tested utility of accuracte and high resolving TOF using protein digest mixtures.
Multi-reflecting time-of-flight mass spectrometers (MR-TOF MS) are known to provide an improved resolving power in the range of 3×104 to 3×105. Prior implementations of MR-TOF MS had narrow mass range because of closing ion trajectories into loops.1,2 To achieve full mass range we suggested to use planar and grid free ion mirrors in combination with periodic lenses in a field free space.3,4 Stable ion confinement and efficient ion transfer have been proven while employing a model ion source – pulsed Cesium gun. Analyzer aberrations were shown to allow resolving power of up to 2×105.
In this study we couple the planar MR-TOF analyzer to an Electrospray ion source by two types of ion pulse converters – an orthogonal accelerator and a linear ion trap with axial ejection.
The orthogonal accelerator is a readily available pulse converter and it conveniently fits the field free space of MR-TOF. It provides the smallest time spread - 3ns for 1kDa ions, which converts into an even higher resolving power of MR-TOF MS (exact data are in progress). The initial ion parameters are well controlled, allowing mass accuracy around 1ppm. However, it has somewhat lower duty cycle compared to the trap converter.
A linear ion trap with pulsed axial ejection is similar to the trap described in.5 Ions are trapped in a small axial DC well near the exit of RF ion guide. Periodically ions are extracted by push and pull pulses on auxiliary electrodes. Efficiency of the ion flux conversion approaches unity. Because of that, the LIT converter may generate extremely intense ion pulses. To prevent space charge effects in the analyzer5 and to sustain “analog counting” regime on the detector, the signal has to be kept under 1000 ions per pulse, i.e. under 1×106 ions per second. The dynamic range reaches 1×105 in spectra, accumulated for one second, which exceeds dynamic range in other types of high resolving instruments - 103 in FTMS (at 1ppm mass accuracy) and 104 in orbitrap.6 The resolving power exceeds 3×104 and low ppm mass accuracy is attainable.
The utility of MR-TOF MS has been examined in LC-MS experiments using model mixtures of protein digests. Enhanced (compared to regular TOF MS) resolving power helps distinguishing minor components and improves analysis capacity (specificity), estimated to be over 104 distinguishable components in the single LC-MS run. Accurate mass and high resolving power help interpreting fragment spectra, generated within the ion interface.
1. H. Wollnik et al., Int. J. Mass. Spectrom. 227, 217 (2003).
2. M. Toyoda et al., J. Mass Spectrom. 38, 1125 (2003).
3. A. Verentchikov et al., Nauchnoe Priborostroenie (Russian) 14, 24 (2004).
4. A. Verenthcikov et al., J. Tech. Physics (Russian), 50, 74 (2005).
5. B. Kozlov et al., ASMS 2005, ASMS 2006 (www.asms.org)
6. A. Makarov et al., Anal. Chem. AC0518811 (2006).