Ion trap analyzers

Ion trap analyzer. A mass-resonance analyzer that produces a three-dimensional rotationally symmetric quadrupole field capable of storing ions at selected mass-to-charge (m/z) ratios. 

It is certainly desirable to have at least sufficient resolution to resolve isotopic patterns to their nominal mass contributions. However, not every mass analyzer is capable of doing so with any ion it can pass through. Such conditions often occur when ions of several thousand u are being analyzed by quadrupole, time-of-flight or quadrupole ion trap analyzers, and hence it is useful to know about the changes in spectral appearance and their effect on peak width and detected mass. [42]... 

In a quadrupole device, not as accurate and precise as double-focusing instruments but fast, a quadrupolar electrical field comprising radio-frequency (RF) and direct-current components is used to separate ions. Quadrupole instruments as mass analyzers are used together with ESI as the ion source the configuration employing a three-dimensional quadrupolar RF electric field (Wolfgang Paul, University of Bonn, 1989 Nobel prize for physics) is referred to as an ion trap analyzer (see below). 

All major mass spectral data collections consist of El mass spectra, mostly recorded under accepted standardized conditions such as an ionization voltage of 70 eV, an emission current of 100-200 xA, and an ion source temperature of 150-200°C. Several types of GC/MS systems may be applied, for instance, magnetic sector, quadrupole, or ion trap analyzers. Ion trap systems are considered less applicable, when data comparison is required with spectra from a reference library. In particular, basic compounds related to VX or the three nitrogen mustards tend to produce protonated molecular ions by self-protonation. Magnetic sector and quadrupole mass spectrometers suffer less from interference of self-protonation, and spectra produced with these types of instruments are generally reproducible. 

Tandem mass spectrometry (MS-MS) using quadrupole mass analyzers or ion-trap analyzers facilitate the conducting MS-MS experiments and increases the sensitivity of detection. Fragmentation patterns of anthocyanins generally show the loss of a glycoside or... 

The HPLC-MS (quadrupole analyzer) and HPLC-MS-MS (medium-class ion-trap analyzer) procedures for the determination of OP metabolites in blood plasma were found to be eomparable in terms of sensitivity, accuracy, and performance, but HPLC-MS is preferred in terms of availability and eost of equipment and maintenance. 

The three-dimensional quadupole field ion trap - or Paul trap is a three-electrode device [see Figure 4.5(b)]. Ions are injected into the device and collected in packets from an ESI or MALDI source. The ion trap analyzer is capable of MS, MS" (MS = MS-MS-MS) and high-resolution scans (R = 20,000). The ion packets enter through an entrance-end cap and are analyzed by scanning the RF amplitude of the ring electrode. The ions are resonated sequentially from low to high m/z and are ejected from the ion trap through the exit-end cap electrode to a detector. Unlike the triple quadrupole (QqQ) mass spectrometer discussed previously, the ion trap performs tandem mass spectrometry (MS-MS) scan modes in the same analyzer. 

Hernando, M. D., Aguera, A., Eemandez-Alba, A. R., Piedra, L., and Contreras, M., Gas chromatographic determination of pesticides in vegetable samples by sequential positive and negative chemical ionization and tandem mass spectrometric fragmentation using an ion trap analyzer. Analyst, 26, 46-51, 2001. 

The most common ion sources used in GC/MS are clcciron-impaci ionization and chemical ionization, Ion sources for mass spectrometry are discussed in detail in Section 20IT The most common mas.s analyzers are quadrupole and ion-trap analyzers. These analyzers arc described in Sections llB-2 and 20C-.T Time-of-flighl mass analyzers are al.so used, but not as frequently as quadrupolcs and ion traps. 

The flexibiHty of being able to switch from El to Cl in the same experiment has contributed to the growing interest in ion trap analyzers. In addition, the Cl potentialities of ion traps have played a major role in establishing ion traps as promising devices for analytical appHcations. Cl operation of the ion trap was reported in 1987, only 3 years after its commercial introduction [6]. The first drawbacks encountered under Cl conditions, space-charge effects and ion-molecule reactions, were circumvented by using modified routine sequences similar to the AGC procedure described below. 

Please note that analytes introduced to GC columns need to be volatile and amenable to detection using the detector at the column outlet. To render less volatile compounds amenable to analysis by GC-MS, derivatization is often conducted by reacting sample components with a generic or specific reagent. While derivatization is normally conducted off-line, in principle, it can be done on-line. In one smdy, a system was developed in which analytes were first separated in an LC column followed by on-line derivatization, and introduction of the resulting mixture to a GC column for further separation and detection by MS using an electron ion source and a quadrupole ion trap analyzer [11]. 

---