Boundary effects and collisional activation in a quadrupole ion trap

Collision-induced dissociation (CID) in a quadrupole ion trap mass spectrometer is usually performed by applying a small amplitude excitation voltage at the same secular frequency as the ion of interest. Here we disclose studies examining the use of large amplitude voltage excitations (applied for short periods of time) to cause fragmentation of the ions of interest. This process has been examined using leucine enkephalin as the model compound and the motion of the ions within the ion trap simulated using ITSIM. The resulting fragmentation information obtained is identical with that observed by conventional resonance excitation CID. "Fast excitation" CID deposits (as determined by the intensity ratio of the a 4 /b 4 ion of leucine enkephalin) approximately the same amount of internal energy into an ion as conventional resonance excitation CID where the excitation signal is applied for much longer periods of time. The major difference between the two excitation techniques is the higher rate of excitation (gain in kinetic energy) between successive collisions with helium atoms with "fast excitation" CID as opposed to the conventional resonance excitation CID. With conventional resonance excitation CID ions fragment while the excitation voltage is still being applied whereas for "fast excitation" CID a higher proportion of the ions fragment in the ion cooling time following the excitation pulse. The fragmentation of the (M ϩ 17H) 17ϩ of horse heart myoglobin is also shown to illustrate the application of "fast excitation" CID to [1] by applying to the end-cap electrodes a small supplementary RF voltage, at the same secular frequency as the ion of interest. This produces an increased amplitude of ion motion for ions of that particular mass-to-charge, which then fragment after collisions with the helium buffer gas. This has been the most popular method used for CID in the quadrupole ion trap mass spectrometer and has been used to study an extremely large range of species. Alternative methods for fragmenting ions within a quadrupole ion trap mass spectrometer have been reported and these include surface induced dissociation [2], photo induced dissociation [3,4], boundary activated dissociation [5][6][7], and red shift off resonance large amplitude excitation [8]. All of these methods, to a greater or lesser extent, have sought to improve the ease of performing CID, the amount of fragmentation information obtained, and the mass range of the product ion spectrum. Here we report studies aimed at increasing the speed of performing a single CID experiment. In a conventional resonance excitation CID experiment a small voltage (e.g., 1 Volt peak-peak ) is applied for a set period of time (e.g., 30 ms) followed by a short cooling time prior to analysis. Here we apply a large voltage (e.g., 20 Volts peak-peak ) for a very short period of time (e.g., 90 s) followed by a short cool time prior to analysis.

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confidence: 99%

“Fast excitation” CID in a quadrupole ion trap mass spectrometer

Murrell

Despeyroux

Lammert

et al. 2003

“…CID in a QIT is usually implemented by applying a supplementary direct current (DC) potential [11][12][13] or alternating current (AC) potential [9,14,15] between a pair of trap electrodes and an auxiliary electric field is produced by the above potential. The mass-selected ions are excited by absorbing energy from the electric field and thus move close to the electrodes; therefore, the ion kinetic energy is increased [16].…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of Dual-Direction Dipolar Excitation of Ions in Linear Ion Traps

Dang

Wang

et al. 2016

Abstract. The ion enhanced activation and collision-induced dissociation (CID) by simultaneous dipolar excitation of ions in the two radial directions of linear ion trap (LIT) have been recently developed and tested by experiment. In this work, its detailed properties were further studied by theoretical simulation. The effects of some experimental parameters such as the buffer gas pressure, the dipolar excitation signal phases, power amplitudes, and frequencies on the ion trajectory and energy were carefully investigated. The results show that the ion activation energy can be significantly increased by dual-direction excitation using two identical dipolar excitation signals because of the addition of an excitation dimension and the fact that the ion motion radius related to ion kinetic energy can be greater than the field radius. The effects of higher-order field components, such as dodecapole field on the performance of this method are also revealed. They mainly cause ion motion frequency shift as ion motion amplitude increases. Because of the frequency shift, there are different optimized excitation frequencies in different LITs. At the optimized frequency, ion average energy is improved significantly with relatively few ions lost. The results show that this method can be used in different kinds of LITs such as LIT with 4-fold symmetric stretch, linear quadrupole ion trap, and standard hyperbolic LIT, which can significantly increase the ion activation energy and CID efficiency, compared with the conventional method.

“…CISE through the use of single frequency and broadband waveform resonance excitation has been reported previously [1]. Another method to increase the kinetic energy of ions and effect dissociation to perform CISE in a quadrupole ion trap is explored in this work.Boundary activation via the manipulation of a z values has been previously investigated and characterized [2][3][4][5][6] and is the method evaluated here. a z is a parameter of the Mathieu second-order differential equations of motions of ions in a quadrupole ion trap.…”

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confidence: 99%

“…Boundary activation via the manipulation of a z values has been previously investigated and characterized [2][3][4][5][6] and is the method evaluated here. a z is a parameter of the Mathieu second-order differential equations of motions of ions in a quadrupole ion trap.…”

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confidence: 99%

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Collision-induced signal enhancement (CISE): The use of boundary activation to effect non-resonant CISE

Asam

Glish

2002

An alternative to resonant excitation collision-induced signal enhancement (CISE) is presented. This alternative utilizes boundary activation instead of resonant excitation to effect CISE and is called boundary activated collision induced signal enhancement (BA-CISE). There are three ways to effect BA-CISE to enhance the signal for an MS nϩ1 experiment. Each technique utilizes the ␤ z ϭ 0 boundary, which ions encounter from high to low mass/charge ratio. BA-CISE is shown to produce an almost 900% increase in the C 2 ion of [maltohexaose ϩ Li] ϩ . The use of a heavy collision gas in addition to the helium bath gas generally produced a signal enhancement inferior to the same experiment without the heavy gas. (J Am Soc Mass Spectrom 2002, 13, 650 -658) © 2002 American Society for Mass Spectrometry C ollision-induced signal enhancement (CISE) is a process whereby the abundance of a second generation, or higher, parent ion for an MS n experiment is increased. The signal increase occurs via two stages of excitation and subsequent dissociation of ions of higher mass/charge ratio than the next generation parent ion. The first stage of excitation/dissociation is of the n-1 generation parent ion and the second stage of excitation/dissociation is of the n-1 generation product ions of higher mass/charge ratio than the n generation parent ion. The viability of CISE as an effective technique depends on the existence of dissociation pathways from ions present in a product ion spectrum to the next generation parent ion. CISE through the use of single frequency and broadband waveform resonance excitation has been reported previously [1]. Another method to increase the kinetic energy of ions and effect dissociation to perform CISE in a quadrupole ion trap is explored in this work.Boundary activation via the manipulation of a z values has been previously investigated and characterized [2][3][4][5][6] and is the method evaluated here. a z is a parameter of the Mathieu second-order differential equations of motions of ions in a quadrupole ion trap. It is defined in equation 1 a z ϭ Ϫ16eUwhere (m) is the mass of the ion, (e) is the electronic charge, (r 0 ) and (z 0 ) are the radial and axial ion trap dimensions, respectively, (⍀) is the ac radial frequency of the trapping voltage, and (U) is the dc voltage amplitude. Since r o , z o , and ⍀ are constants of a given quadrupole ion trap, for a given mass/charge ratio, the a z value is only dependent upon the dc voltage. The other parameter in the Mathieu equations is q z and it is defined in equation 2.