Ion trap/TOF

It should be pointed out that FAB, MALDI, and ESI can be used to provide ions for peptide mass maps or for microsequencing and that any kind of ion analyzer can support searches based only on molecular masses. Fragment or sequence ions are provided by instruments that can both select precursor ions and record their fragmentation. Such mass spectrometers include ion traps, Fourier transform ion cyclotron resonance, tandem quadrupole, tandem magnetic sector, several configurations of time-of-flight (TOF) analyzers, and hybrid systems such as quadrupole-TOF and ion trap-TOF analyzers. 

Q Quadrupole, IT Ion trap, ToF Time of flight, ICR Ion cyclotron resonance... 

Collings, B.A. Campbell, J.M. Mao, D. Douglas, D.J. A Combined Linear Ion Trap TOF System With Improved Performance and MS Capabilities. Rapid Commun. Mass Spectrom. 2001, 75, 1777-1795. 

Ion trap/TOF This combination is advantageous because it enables the MS" capabilities of an ion trap with the high mass accuracy and speed of a TOF analyzer. The ion trap can either be a conventional hyperbolic Penning-type device or a linear trap device. Below we describe the deployment of the former type ion trap/TOF for explosives detection. 

MALDI-Fourier transform ion cyclotron resonance mass spectrometry MALDI-Q-ion mobility-TOFMS MALDI-Quadrupole-ion-trap-TOF mass spectrometry MALDI-TOF-imaging mass spectrometry MALDI Time-of-flight mass spectrometry Magnetic resonance imaging Matrix solution fixation Moxifloxacin... 

The MALDI-Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (MALDI-FT-ICR-MS) and MALDI-Quadrupole-Ion-trap-TOF Mass Spectrometry (MALDI-QIT-TOF-MS) can be used on IMS. The FT-ICR-MS could provide the high resolution, expansive mass range and high sensitivity imaging MS data and good for determining the elemental composition of small molecules [60],... 

A 30-lb field-portable quadrupole ion trap TOF (QitTof) mass spectrometer with an atmospheric photoionization source was constructed [17]. The photoionization source has the ability to choose a narrow-band ionization energy that is sufficiently high to ionize and detect most compounds of interest but low enough to avoid ionization of most common air constituents, such as N2, 02, H20, C02, CO, Ar, etc. Fragmentation is minimal because ionization occurs just above the ionization thresholds, with very little excess energy. The ion trap stores ions from a continuous ionization source followed by pulsed extraction into the TOF mass analyzer. 

Two peaks are considered to be resolved if the valley between them is equal to 10 % of the weaker peak intensity when using magnetic or ion cyclotron resonance (ICR) instruments and 50 % when using quadrupoles, ion trap, TOF, and so on. If Am is the smallest mass difference for which two peaks with masses m and m + Am are resolved, the definition of the resolving power R is R = ml Am. Therefore, a greater resolving power corresponds to the increased ability to distinguish ions with a smaller mass difference. 

Quadrupole Ion trap TOF TOF reflectron Magnetic FTICR Orbitrap... 

A TOF mass analyser requires a pulsed ion introduction. In an electrospray-TOF combination, the duty cycle is an important issue. A significant improvement in the duty cycle can be achieved in an ion-trap-TOF hybrid instmment the ions from a continuous ion source are accumulated in the ion trap between two ion introduction events. An ion-trap-TOF hybrid instrument was first described by the group of Lubman [68-69]. The system consists of an atmospheric-pressure ion source with a vacuum interface, a set of Einzel lenses, an ion-trap device, and a reflectron time-of-flight mass analyser. The system was applied for fast analysis in combination with a variety of separation techniques [70]. 

ToF analyzers as well as hybrid instruments that combine two or more mass-resolving components, such as quadrupole-ToF (Q-ToF), ion-mobility ToF, and ion-trap-ToF, as well as the high-resolving Fourier transform (FT) analyzer Orbitrap and ion cyclotron resonance (ICR). For targeted analysis, a multiple-reaction monitoring instrument based on triple-quadrupole technologies (QQQ) has provided unrivaled sensitivity for MSI of pharmaceuticals, yet its targeted nature renders it unsuitable for discovery-based research. 

The ESI and APCI are both soft ionization techniques, hence the spectra obtained using these methods are usually very simple and consist predominantly of the pseudomolecular ion. When more information is required, tandem mass spectrometry is a popular option. Several different types of tandem LC/MS systems can be found, with triple quadrupole and ion trap being the most popular choices. Hybrid systems including magnetic sector-quadmpole, magnetic sector-TOF, quadrupole-TOF (Q-TOF) and ion trap-TOF have been described. The most successful among these hybrids is the Q-TOF instrument. 

There are several ways to perform fragmentation depending on the geometry of the mass spectrometer. Examples of such systems are triple quadrupole MS, ion trap, ion trap-ToF, ToF-ToF, ion trap-Orbitrap, and quadrupole-Orbitrap. It is considered to be bqrond the scope of this book to describe fragmentation in more detail. 

Hybrid instruments include the BEqQ spectrometer (magnetic sector, B electric sector, E RF-only quadrupole, q quadrupole mass analyzer, Q) and the BTOF (magnetic sector, B TOF analyzer, TOF) spectrometer. The QqTOF spectrometer is similar to the triple quadrupole (QqQ) instrument except that the final quadrupole mass analyzer is replaced with a TOF analyzer. In another variant, the Qq section can be replaced by a quadrupole ion trap to yield an ion-trap-TOF instrument. 

Neither of these approaches to fragmentation achieve the tandem (MS-MS) capabilities that should be possible using the ion-trap TOF combination. With the addition of a supplementary rf voltage on the endcaps it should indeed be possible to isolate the molecular ions of a particular analyte in a mixture and provide resonant excitation of a given molectdar ion prior to extraction of the ions into the time-of-flight mass analyzer. 

Feature Double-focusing sector Linear quadrupole Ion trap TOF... 

---