A new technique for decomposition of selected ions in molecule ion reactor coupled with ortho-time-of-flight mass spectrometry

The mass-selective manipulation of ions at elevated pressure, including mass analysis, ion isolation, or excitation, is of great interest for the development of mass spectrometry instrumentation, particularly for systems in which ion traps are employed as mass analyzers or storage devices. While experimental exploration of high-pressure mass analysis is limited by various difficulties, such as ion detection or electrical discharge at high-pressure, theoretical methods have been developed in this work to study ion/neutral collision effects within quadrupole ion traps and to explore their performance at pressures up to 1 Torr. Ion trapping, isolation, excitation, and resonance ejection were investigated over a wide pressure range. The theoretically calculated data were compared with available experimental data for pressures up to 50 mTorr, allowing the prediction of ion trap performance at pressures more than 10 times higher. (J Am Soc Mass

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confidence: 82%

Ion trap mass analysis at high pressure: A theoretical view

Song

Smith

et al. 2009

“…For example, generation of an axial electric field by segmenting the multipole rods themselves has been extensively characterized [11][12][13][14][15][16][17]. Other methods for producing an axial electric field include conical (rather than fixed-diameter) multipole rods [18], offsetting one end of the multipole from the central (z-) axis [14], encasing the multipole with segmented rings [15,19], and the insertion of electrodes between parallel rods [20,21].…”

Section: T He Interface Of Electrospray Ionization (Esi) Withmentioning

confidence: 99%

Improved ion extraction from a linear octopole ion trap: SIMION analysis and experimental demonstration

Wilcox

Hendrickson

Marshall

2002

150

138

Externally generated ions are accumulated in a linear octopole ion trap before injection into our 9.4 T Fourier transform ion cyclotron resonance (FT-ICR) mass analyzer. Such instrumental configuration has previously been shown to provide improved sensitivity, scan rate, and duty cycle relative to accumulated trapping in the ICR cell. However, inefficient ion ejection from the octopole currently limits both detection limit and scan rate. SIMION 7.0 analysis predicts that a dc axial electric field inside the linear octopole ion trap expedites and synchronizes the efficient extraction of the octopole-accumulated ions. Further SIMION analysis optimizes the ion ejection properties of each of three electrode configurations designed to produce a near-linear axial potential gradient. More efficient extraction and transfer of accumulated ions spanning a wide m/z range promises to reduce detection limit and increase front-end sampling rate (e.g., to increase front-end resolution for separation techniques coupled with FT-ICR mass analysis). Addition of the axial field improves experimental signal-to-noise ratio by more than an order of magnitude. (J Am Soc Mass Spectrom 2002, 13, 1304 -1312

“…Of particular importance is the collisional activation of ions in radio frequency (RF) ion traps and guides, where a substantial bath gas pressure and long residence times result in large numbers of the ionneutral collisions [6]. Several research groups have proposed using the effective temperature as a measure of ion activation under conditions of multiple ionneutral collisions [7][8][9][10][11][12]. As such, the effective temperature concept proved to be very useful in the interpretation of ion activation data obtained for various mass spectrometry experiments, in particular in quadrupole ion trap experiments [8,9,[13][14][15].…”

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confidence: 99%

“…We consider the kinetics of collisional heating of ions using the characteristic ion heating time. It was previously suggested that this characteristic time is of the same order of magnitude as the velocity relaxation time [10]. Here, we present a more accurate estimation of the characteristic ion heating time based on recent findings for the thermal energy in polyatomic biomolecules, including peptide ions [23].…”

mentioning

confidence: 99%

Collisional activation of ions in RF ion traps and ion guides: The effective ion temperature treatment

Tolmachev

Vilkov

Bogdanov

et al. 2004

Ion transfer and storage using inhomogeneous radio frequency (RF) electric fields in combination with gas-assisted ion cooling and focusing constitutes one of the basic techniques in mass spectrometry today. The RF motion of ions in the bath gas environment involves a large number of ion-neutral collisions that leads to the internal activation of ions and their effective "heating" (when a thermal distribution of internal energies results). The degree of ion activation required in various applications may range from a minimum level (e.g., slightly raising the average internal energy) to an intense level resulting in ion fragmentation. Several research groups proposed using the effective temperature as a measure of ion activation under conditions of multiple ion-neutral collisions. Here we present approximate relationships for the effective ion temperature relevant to typical operation modes of RF multipole devices. We show that RF ion activation results in near-thermal energies for ions occupying an equilibrium position at the center of an RF trap, whereas increased ion activation can be produced by shifting ions off-center, e.g., by means of an external DC electric field. The ion dissociation in the linear quadrupole ion trap using the dipolar DC ion activation has been observed experimentally and interpreted in terms of the effective ion temperature. ollisional activation of ions takes place in all practical mass spectrometry measurements, either as a side effect of a residual gas pressure, or for the specific purpose of collisional ion cooling, focusing or collision induced dissociation. Modeling of the collisionally induced ion activation process in mass spectrometry has been the focus of extensive study [1][2][3][4][5]. Of particular importance is the collisional activation of ions in radio frequency (RF) ion traps and guides, where a substantial bath gas pressure and long residence times result in large numbers of the ionneutral collisions [6]. Several research groups have proposed using the effective temperature as a measure of ion activation under conditions of multiple ionneutral collisions [7][8][9][10][11][12]. As such, the effective temperature concept proved to be very useful in the interpretation of ion activation data obtained for various mass spectrometry experiments, in particular in quadrupole ion trap experiments [8,9,[13][14][15]. Generally, the internal energy of ions produced at high pressures (e.g., by the electrospray ionization process) can be characterized in terms of effective ion temperature [16 -20]. The effective temperature T eff of an ion, moving in a bath gas under the influence of electric fields, can be expressed through the ion drift velocity V drift as follows:2 , where T is the gas temperature, and C T is a model dependent proportionality coefficient [9,12,21]. This approximation is applicable to conditions when the force acting on an ion is constant during a time interval longer than the ion velocity relaxation time (i.e., the drift motion approximation) [22]. In the lower ...