Models for mass-independent space and energy focusing in time-of-flight mass spectrometry

Yefchak, George E.; Enke, Christie G.; Holland, John F.

doi:10.1016/0168-1176(89)80031-x

Cited by 40 publications

(14 citation statements)

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“…No change in hardware is required whereas a similar approach to improve mass resolution in TOF/MS, employing dynamic post-source acceleration, is accomplished using an additional short-range dynamic field region. 5 The approach proposed here may provide higher mass resolution in the MALDI-TOF technique. The only necessary parameter for each specific TOF instrument is the geometric parameter η 0 = 2d/L, where d and L are the lengths of ion source and field-free drift tube.…”

Section: Discussionmentioning

confidence: 98%

An Approach to the Design of Mass-correlated Delayed Extraction in a Linear Time-of-flight Mass Spectrometer

Kovtoun

1997

Rapid Commun. Mass Spectrom.

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An algorithm is suggested that allows the implementation of first order velocity (energy) focusing in a linear, single field, time-of-flight mass spectrometer (TOF/MS) over a broad mass range using a time-dependent mass-corrected extraction field. The interpolation formula for extraction field dependence on time for a particular geometry of TOF/MS is presented. There are two values that determine the expression for temporal dependence of the extraction field: the geometry scale parameter (the ratio of the ion source and field-free drift tube lengths) and the initial point (low-mass limit) of scanning in the mass spectrum. © 1997 by John Wiley & Sons, Ltd. Received 17 January 1997; Accepted 27 January 1997 Rapid Commun. Mass Spectrom. 11, 433-436 (1997 Here, DE provides reduced energy losses during the initial stage of ion drift through desorbed gaseous matrix substance in the extraction field.The main problem of the velocity focusing using DE is the narrow mass range in focus because the optimum time delay, T, is a mass-dependent parameter. In the single-field linear TOF mass-spectrometer: . The quality of the mass spectra is gradually degraded on moving away, to both sides, from the optimum value of m 0 . The need to obtain a broad, high quality mass spectrum, especially for fragmentation studies of large nucleotides and proteins has, stimulated the search for ways to overcome the limitations inherent in the conventional DE method. THEORYLet us consider the standard, linear, single-field TOF mass spectrometer. Also consider a model, broadrange, mass spectrum ranging from the low-mass limit, m 0 , to the high-mass limit M 0 .First, the time delay, T, is chosen to provide optimum energy focusing conditions only for the low-mass limit (m 0 ) ion. At the moment that the ion of mass m 0 reaches the exit grid of the ion source (the plane x = d), the extraction field is slightly adjusted to improve focusing conditions for the subsequent ion of mass m = m 0 + δm.The strategy is formulated as follows. It is necessary to restore a time dependence of the extraction-field function U(t) that enables first order energy focusing for every successive ion of mass m > m 0 . One can define a reduced voltage function u(t) = U(t)/U 0 , for which t ≥ T, (U(t = T) = U 0 ). Then, for an ion of mass m, the equation of motion in the ion source is:Upon integration of (2) this gives:

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Section: Discussionmentioning

confidence: 98%

An Approach to the Design of Mass-correlated Delayed Extraction in a Linear Time-of-flight Mass Spectrometer

Kovtoun

1997

Rapid Commun. Mass Spectrom.

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“…Of course, from the standpoint of sensitivity and throughput, focusing is superior to filtering. However, one cannot achieve both spatial and energetic focusing through any combination of static fields (4). Therefore, the current practice is to achieve focus for one variable and minimize the effect of the other.…”

Section: Ion Focusing In Distance-of-flight and Time-of-flight Mass Smentioning

confidence: 99%

Distance-of-Flight Mass Spectrometry: A New Paradigm for Mass Separation and Detection

Enke

Ray

Graham

et al. 2012

Annual Rev. Anal. Chem.

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Distance-of-flight mass spectrometry (DOFMS) offers the advantages of physical separation of ions, array detection of ions, focusing of initial ion energy, great simplicity, and a truly unlimited mass range. DOFMS instrumentation is similar to that of time-of-flight mass spectrometry (TOFMS) and shares its ion-source versatility, batch analysis, and rapid spectral-generation rate. With constant-momentum ion acceleration and an ion mirror, there is a time at which ions of all mass-to-charge values are energy focused at their particular distances along the flight path. A pulsed field orthogonal to the flight path drives the ions to reach the detector array at this specific time. Results from a 0.29-m proof-of-principle instrument verify the theoretically predicted energy focus and demonstrate how the range of mass-to-charge values that impinge on the detector array can be readily changed. DOFMS could be combined sequentially with TOFMS to enable simultaneous scanless tandem mass spectrometry.

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“…Efforts are still being made to improve the resolving power of the conventional commercial Wiley-McLaren instrument. Sanzone et al (41) have proposed an impulse field focussing technique whilst Enke's group (42) have considered various models for mass-independent space and energy focussing. Muga (43) has developed a commercial instrument based on a 'velocity compaction' technique in which a time-dependent acceleration voltage is used to compensate for the translational energy spread of ions ejected from a Wiley-McLaren ion source.…”

Section: Essentialmentioning

confidence: 99%

Time-of-Flight Mass Spectrometry

Price

1993

ACS Symposium Series

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As shown in Table I, time-of-flight mass spectrometry has had a checkered history since it became commercially available following the innovations of the Wiley-McLaren design in 1955. The Bendix/CVC instruments were used for a wide range of applications facilitated by its very fast scan capability and/or ease of access to the ion source. However, because they were seen as having both low resolution and low sensitivity, these instruments never became widely utilised in the major areas of mass spectrometry.The resurgence of interest in the time-of-flight technique since the mid '80's has been due to the advent at the forefront of mass spectrometry development of such techniques as laser and plasma desorption, laser ionisation and surface analysis, which require its ability to provide a complete spectrum for each ionisation event and also its unlimited mass range. In order for this renaissance to continue and expand, a wide base of commercially available instruments is required. As can be seen from Table II such a base now exists. This chapter is intended to provide a brief history of the time-of-flight mass spectrometer (TOFMS) over the period 1955-90 based on the progress reported at various European time-of-flight symposia. In this it is intended to act as a prelude to the exciting developments which this author anticipates for the current decade. The following chapters will provide the reader with a foretaste of the future of time-of-flight mass spectrometry.Time-of-flight mass spectrometers operate on the simple principle that a packet of ions, of differing mass/charge (m/z) ratios but equal energy or momentum, when projected into a constant electric field will separate according to their m/z ratios. Since ζ is usually unity, the separation is essentially one of mass. If the ions travel a fixed distance / to a detector, then the 'time-of-flight' (TOF) is given by 1/2 r λ l 2 m 2V ζ V J ^ J in the constant energy case (V is the accelerating voltage) and

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Models for mass-independent space and energy focusing in time-of-flight mass spectrometry

Cited by 40 publications

References 9 publications

An Approach to the Design of Mass-correlated Delayed Extraction in a Linear Time-of-flight Mass Spectrometer

An Approach to the Design of Mass-correlated Delayed Extraction in a Linear Time-of-flight Mass Spectrometer

Distance-of-Flight Mass Spectrometry: A New Paradigm for Mass Separation and Detection

Time-of-Flight Mass Spectrometry

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