Mass range extension

Greaser, C.S. Stygall, J.W. A Comparison of Overtone and Fundamental Resonances for Mass Range Extension by Resonance Ejection in a Quadrupole Ion Trap Mass Spectrometer. Int. J. Mass Spectrom. 1999,190/191, 145-151. 

Kaiser, R. E., Jr., Cooks, R. G., Moss, J. and Hemberger, P. H. Mass range extension in a quadrupole ion-trap mass spectrometer. Rapid Commun. Mass Spectrom. 3 50-53,... 

Magpaiangalan, D.P. Garrett, T.J. Diexler, D.M. Yost, R.A. Analysis of Large Peptides by MALDI Using a Linear Quadrupole Ion Trap With Mass Range Extension Anal. Chem. 2010, 82, 930-934. 

In Eq. (9.8), V max is the maximum amplitude of the RF and z ject is the point on the stability diagram where the ions are resonantly ejected. By using a lower z-eject, however, the scan rate (Th s ) increases, but resolution is reduced. In the example above, the scan rate would be increased to 55,550 Th s . This rapid scan rate will also result in fewer points acquired across a mass peak unless a higher data acquisition rate is used (see Section 9.3.3.3, The Effects o/Scan Rate The Normal, Rapid, and Slow Scan Rates )- A solution to this problem would be to reduce the scan rate back to 5555 Th s and to limit the mass range to avoid long scan times. Mass range extension in the LQIT can be accomplished by applying the same methods as described above. 

Instrumental developments concern micro ion traps (sub-mm i.d.) [193], extension of the mass range, mass resolution and capture efficiency for ions generated externally. Fast separations at very low detection levels are possible by means of hybrid QIT/reToF mass spectrometry [194]. 

MALDI evolved from a progression of similar ionization techniques developed from the late 1960s, coinciding with the introduction of laser technology.17 Unfortunately, such laser desorption (LD) techniques were limited to an upper mass range of approximately mjz 2000 and because of the high laser fluences required for LD, extensive thermal degradation of the analyte was often observed. 

FT/ICR experiments have conventionally been carried out with pulsed or frequency-sweep excitation. Because the cyclotron experiment connects mass to frequency, one can construct ("tailor") any desired frequency-domain excitation pattern by computing its inverse Fourier transform for use as a time-domain waveform. Even better results are obtained when phase-modulation and time-domain apodization are used. Applications include dynamic range extension via multiple-ion ejection, high-resolution MS/MS, multiple-ion simultaneous monitoring, and flatter excitation power (for isotope-ratio measurements). 

Dynamic range extension in GD quadrupole/ion-trap MS based on selective ion-accumulation (e.g. by mass-selective instability, single-frequency resonance ejection, combined rf-dc and entrance end-cap dc methods) allows the selective accumulation of the analyte ions and enables the dynamic range to be increased by a factor of 105 [233]. The linearities and relative trapping efficiencies of the previous methods were assessed with respect to the injection time and the methods were used for the GD ion-trap MS determination of major and minor constituents in NIST SRM 1103 Free Cutting Brass. 

A major advantage is the extension of the mass range to approximately double the actual mass limits, e.g., in the eicos-tetcos nucleotides (n = 20-24) range. This half-sequence method with the appropriate computer pro-... 

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