Ion trap analyser

Figure 6.16 Schematic of ion trap analyser (internal ion source)...

Table 6.32 Main characteristics of ion trap analysers Advantages...

Figure 4.5 Mass spectrum of synthesised tetracosanyl palmitate obtained by Dl El MS on a GCQ Finnigan device equipped with an ion trap analyser. Adapted from Regert and Rolando, 2002...

Figure 4.11 Mass spectrum of an archaeological sample made of a mixture of beeswax and birch bark tar from a residue sampled on a ceramic sherd from the Iron Age site of Grand Aunay (Sarthe, France). The spectrum was obtained by Dl El MS on a GCQ Finnigan device equipped with an ion trap analyser. Adapted from Regert and Rolando, 2002 (see colour Plate 1)...

In addition to the diversity of ionisation techniques available, mass spectrometers offer a selection of mass analyser configurations. Of note are single (MS) and triple quadrupole (MS—MS) instruments, ion trap analysers (MS)n, time-of-flight (ToF) analysers, sector field analysers, and Fourier transform-ion cyclotron resonance (FTICR) instruments. 

However, nowadays some other different mass spectrometers are used for ICP-MS time-of-flight (TOP) systems for multielemental analysis of transient signals, ion trap analysers for ion storage, multicollector instruments for precise isotope ratio measurements and double-focusing sector field mass spectrometers for high mass resolution, but still the majority of instruments are equipped with quadrupole filters, which are simpler and cheaper. 

Swiderek, K. M. Davis, M. T. Lee,T. D. 1998. The identification of peptide modifications derived from gel-separated proteins using electrospray triple quadrupole and ion trap analyses. Electrophoresis, 19,989-997. 

Ion Trap Analyser Combined with Time-of-Flight or Ion Cyclotron Resonance... 

To bring the power of ECD to ion trap analysers, a new ECD-like activation method has been developed [58]. This method, which is called electron transfer dissociation (ETD), uses gas-phase ion/ion chemistry to transfer an electron from singly charged aromatic anions to multiply charged ions. The mechanism of this method and the observed fragmentation pathways are analogous to those observed in ECD. 

Ion trap analyser a mass analyser in which ions are confined in space by means of one or a combination of electric fields, AC or DC, capable of storing ions within a... 

Ion trap analysers use a similar principle to quadrupole mass analysers but employ a system of entrance, exit and end-cap electrodes together with a ring electrode that surrounds the trap cavity (Figure 9.10). As with quadrupole so with ion trap, for each ion type with a given value of m/z there is a corresponding value of interactions between ion type and external quadrupole field are such as to enable the trapping of ion within the analyser prior to release for detection. Ion traps are relatively inexpensive, quite sensitive and robust, so are fairly widespread, despite being less accurate than TOF and quadrupole mass analysers. 

There are two main groups of analysers, non-magnetic analysers typified by quadrupoles and ion trap analysers and magnetic analysers which use permanent or electromagnets to separate the ions under the influence of a magnetic field. 

There are some limitations of the ion trap analyser in that it is subject to space-charge effects. These effects are a consequence of too many ions present in the trap, which results in a distortion of the electrical field. This in turn leads to a reduction in the overall performance of the analyser. This type of analyser can be used up to m/z values of up to 4,000 Da, as with the quadrupole. The main difference between the quadrupole and the ion trap analyser is that quadrupoles act as a continual mass filter with ions continuously transferred to the quadrupole from the ion source, whereas ion trap analysers selectively trap ions of certain m/z values. 

The linear ion trap analyser is a variation of the ion trap analyser introduced to combat some of the problems that had been encountered with the ion trap in relation to the space-charge effects. The Unear ion trap utilises two trapping electrode rings on the end of a quadrupole. This allows the instrument to be used in a normal scanning quadrupole mode it also allows for the end electrodes to be switched on to retain only specific ions in the trap for collision with the damping gas. 

The major difference between these analysers and normal ion trap analysers is that they have a much greater capacity for trapping within the volume between the rods of the quadrupole (as opposed to in the centre of the ring electrode or the normal ion trap). This results in a greater sensitivity for... 

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