Time-of-flight detectors

In some studies the LC has been coupled to triple quadrupole and time-of-flight detectors. Moco and others (2006) used this technique to study phytochemicals including... 

The presently used detector system is composed of three time-of-flight detectors, seven identical 16-strip silicon wafers, and germanium detectors [15]. A schematic view of the detector arrangement is shown in the focal plane of SHIP in Figure 1. Three secondary-electron foil detectors in front of the silicon detectors are used to measure the velocity of the particles [18]. They are mounted 150 mm apart from each other. The detector signals are also used to distinguish implantation from radioactive decays of previously implanted nuclei. Three detectors are used to increase the detection efficiency. 

The first level LI corresponds to the electronically excited Cr(CO)6 (fl Tlu) and L5 is the ground state (S0) of Cr(CO)5. Each of these levels produces a different range of ionized fragments following application of the probe pulse. The time-of-flight detector can select ions of a particular mass, and the time-dependent behavior of each fragment ion provides information on the length of time taken for the system to traverse each of the five levels. 

At 1 MeV/amu energies, the dE/dx and total energy measurements are made with either gas ionization detectors or silicon surface-barrier detectors or a combination of these. The time-of-flight detector serves as an additional positive-ion mass analysis stage. It is most useful for the heaviest (slowest) ion such as I and consists of two time-pickoff detectors with time resolution of a few hundred picoseconds. 

M+Me] (where Me denotes a metal as for example Na or K present in the used matrix). The ionized macromolecules are accelerated in an electric field and enter the time-of-flight detector. 

L He, L Liang, DM Lubman. Continuous-flow MALDI mass spectrometry using an ion trap/reflection time-of-flight detector. Anal Chem 67 4127, 1995. 

Figure 2.12 illustrates the mass spectrum of a narrow-dispersed polystyrene sample recorded using a Secondary Ion Mass Spectrometer equipped with a time-of-flight detector (TOF-SIMS). There are a series of mass spectral peaks due to ions of the type H-(St) -C4H9, Ag (silver was added as a cationization agent). Equahon (2.1) yielded Mn = 4550, which is within 8% with the value Mn = 4964 obtained by VPO. 

Newer mass spectrometers use a simple time-of-flight detector that measures the time the positively charged particles take to travel to the part of the detector that records the impact of the ion. The longer a particle takes to travel the distance, the greater its mass. Another common type of mass spectrometer uses a quadrupolar electrostatic held to sort ions by their masses. 

Regarding MS instruments, time-of-flight detectors provide elevated mass resolution and accuracy over a broad mass of range, and thus help structural elucidation of nontargeted compounds based on accurate mass measurements and isotopic patterns. Triple quadrupole instmments are particularly well suited for targeted analysis and provide excellent sensitive and selectivity by performing tandem MS/MS analysis [71]. 

LOD, limit of detection MRM, multiresidue method DW, drinking water RW, river water GW, groimdwater TFA, trifluoroacetic acid MS, mass spectrometer detector SW, surface water DAD, diode-array detector UV, ultraviolet detector TOF, time-of-flight detector Q-TOF, quadrupole-time-of-flight detector. 

Figure 23.31 Time-of-flight detector system. Adapted with permission from Ref. [141] 1989, AlP Publishing LLC.

A typical detection setup at the focal plane of a kinematic separator includes transmission time-of-flight detectors followed by a stopping position-sensitive semiconductor detector. The time-of-flight detectors are used to tag energy signals... 

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