Ion storage

In IMR-MS an ion storage section is created, into which ions from a conventional El ion source are injected and... 

Ion trap MS is particularly suited for chemical structure elucidation, as it allows for simultaneous ion storage, ion activation and fragmentation, and product ion analysis. The fragmentation pathway of selected ions and the fragmentation products provide information on the molecular structure. Compared with triple-quadrupole and especially with sector instruments, the ion trap instrument provides more efficient conversion of precursor ion into product ions. However, the CID process via resonance excitation, although quite efficient in terms of conversion yield, generally results in only one (major) product ion in the product-ion mass spectrum. MS/MS with a quadrupole ion trap offers a number of advantages ... 

We will be rather brief in describing the principles of the experimental methods that are most commonly used in studies of dissociative recombination, afterglows and colliding beams (merged beams and ion storage rings). It should suffice to recount some of their generic properties. 

After publication of the ion-storage-ring data, new recombination mechanisms were proposed1 that do not require crossings between ionic and neutral potential curves. However, no detailed calculations have been made for Hj and it is not yet clear if such mechanisms are capable of explaining the experimental findings. 

Idota Y., Kubota T., Matsufuji A., Maekawa Y., Miyasaka T. Tin-Based Amorphous Oxide A High-Capacity Lithium-Ion-Storage Material. Science 1997 276 1395-97. 

Linear quadmpole ion trap LIT Continuous ion beam and trapped ions storage and eventually separation in linear radio frequency quad-rapole field due to stability of trajectories... 

Wilhelm, U. Aicher, K.P. Grotemeyer, J. Ion Storage Combined With Reflec-tron TOF Mass Spectrometry Ion Cloud Motions As a Result of Jet-Cooled Molecules. Int. J. Mass Spectrom. Ion Proc. 1996,152, 111-120. 

Figure 2.30 Scheme of a solid electrochromic device. The device can operate with two electrochromic films as shown or with an electrochromic and an ion-storage film. 

By applying a fundamental RF potential, the QIT can be described as a small ion storage device where ions are focused toward the center of the trap by collision with helium gas. In the QIT, because of the cylindrical symmetry of the trap, the x and y components of the field are combined to a single radial r component, where + y. The motion of ions in the trap is characterized by one... 

Essentially, the ion storage trap is a spherical configuration of the linear quadrupole mass filter. The operations, however, differ in that the linear filter passes the sorted ions directly through to the detector, whereas the ion trap retains the unsorted ions temporarily within the trap. They are then released to the detector sequentially by scanning the electric field. These instruments are compact (benchtop), relatively inexpensive, convenient to use, and very sensitive. They also provide an inexpensive method to carry out GC/MS/MS experiments (Section 2.2.7) (GC is gas chromatography). 

FIGURE 2.4 (6). Quadrupole ion storage trap with attached gas chromatograph. The ionizing unit is external to the ion trap. With permission of the American Society of Mass Spectrometry. From What is Mass Spectrometry ... 

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. 

The two-dimensional (2-D) or linear ion trap (LIT) emerged in the 2000s as an effective alternative to the 3-D trap. Before 1995, linear traps were used primarily as ion storage/transfer/ion-molecule reaction devices in combination with FTICR (Senko et al., 1997 Belov et al., 2001), TOF (Collings et al., 2001), 3D ion trap (Cha et al., 2000), and triple-quadrupole (Dolnikowski et al., 1988) mass spectrometers because LITs offer better ion storage efficiencies in comparison to 3D quadrupole ion traps of the same dimensions (Hager, 2002 Schwartz et al., 2002). In 2002, commercial LITs were introduced as either stand-alone mass spectrometers (Schwartz et al., 2002) or as part of a triple quadrupole mass spectrometer (Hager, 2002). 

The commercially available stand-alone LITs, marketed under the name LTQ, are made of four hyperbolic cross-sectional rods (Fig. 1.25). Since ions are trapped in an axial mode as opposed to central trapping on 3D ion traps, LTQs have been successfully coupled with Orbitrap and FTICR for achieving high-resolution capabilities (Peterman et al., 2005 Sanders et al., 2006) (Chapter 5). Functional improvements in 2D traps over 3D traps include 15 times increase in ion storage capacity, 3 times faster scanning, and over 50% improvement in detection efficiency and trapping efficiency. 

In recent years, linear (or 2D) ion trap mass spectrometers have been developed to improve detection limits over the traditional ion traps (Hager, 2002 Schwartz et al., 2002). In addition, LITs have greater ion storage capacities that increase the number of ions that can be trapped, and hence detected, without space charge effects. 

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