Hybrid mass spectrometer advantages

A TOF analyzer can be used alone or in conjunction with other analyzers to function as a hybrid mass spectrometer. The hybrids provide advantages not attainable, or difficult to attain by the... 

The AutoSpec -TOF hybrid mass spectrometer combines the advantages of a magnetic/electric-sector instrument with those of time-of-flight to give a versatile instrument capable of MS or MS/MS at high or low resolution. 

The term Q/TOF is used to describe a type of hybrid mass spectrometer system in which a quadrupole analyzer (Q) is used in conjunction with a time-of-flight analyzer (TOP). The use of two analyzers together (hybridized) provides distinct advantages that cannot be achieved by either analyzer individually. In the Q/TOF, the quadrupole is used in one of two modes to select the ions to be examined, and the TOF analyzer measures the actual mass spectrum. Hexapole assemblies are also used to help collimate the ion beams. The hybrid orthogonal Q/TOF instrument is illustrated in Figure 23.1. 

The TOF mass analyzer has a low duty cycle, and the combination with an ion accumulation device such as an ion trap is therefore very advantageous. It offers also MS capabilities with accurate mass measurement. In all acquisition modes, the ions are accelerated into the time of flight for mass analysis. Various other hybrid mass spectrometers with TOF have been described, including quadrupole ion trap [70] and linear ion trap [58]. High energy tandem mass spectrometry can be performed on TOF-TOF mass spectrometers [71, 72]. 

Hybrid time-of-flight (TOF) mass spectrometers make use of a TOF analyzer placed at right angles to a main ion beam. Ions are deflected from this beam by a pulsed electric fleld at right angles to the ion beam direction. The deflected ions travel down the TOF tube for analysis. Hybrid TOF mass spectrometers have many advantages arising from the combination of two techniques, neither of which alone would be as useful. 

Each type of mass spectrometer has its associated advantages and disadvantages. Quadrupole-based systems offer a fairly simple ion optics design that provides a certain degree of flexibility with respect to instrument configuration. For example, quadrupole mass filters are often found in hybrid systems, that is, coupled with another surface analytical method, such as electron spectroscopy for chemical analysis or scanning Auger spectroscopy. 

A triple-quadrupole linear ion trap (QqLIT), which is the most widely used hybrid linear ion trap, is based on the ion path of a triple-quadrupole mass spectrometer with Q3 operated as either a conventional RF/DC quadrupole mass filter or a linear ion trap mass spectrometer. " A QqLIT combines the advantages of a QqQ and a QIT within the same platform without compromising the performance of either mass spectrometer. It retains classical QqQ functions such as MRM, product ion scan, precursor ion scan, and constant neutral loss scan for quantitative and qualitative analysis, and possesses MS" ion accumulation... 

An alternative approach was introduced by Hunt and co-workers [87], Those researchers coupled a linear quadrupole ion trap, consisting of four rods of hyberbolic cross-section, with an FT-ICR mass spectrometer. The linear ion trap allows accumulation of larger populations of ions than does a standard three-dimensional (3D) ion trap. The hybrid linear ion trap-FT-ICR instrument enables simultaneous detection in both mass analyzers. This aspect is particularly advantageous for data-dependent MS/ MS methods used in proteomics, and is discussed further below. The commercial version of this instrument features automated gain control that accumulates a fixed number of charges before delivery to the ICR cell. Because the ideal ion density is attained in the cell, space-charge effects resulting in loss of mass resolution and mass accuracy, are eliminated. 

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