A segmented ring, cylindrical ion trap source for time-of-flight mass spectrometry

Abstract

An ion trap source has been designed for use with time-of-flight (TOF) mass analysis. Two thin diaphragms make up a segmented ring electrode; the end cap electrodes are planar wire mesh. The potential field produced by the rf voltage applied between the ring and end cap electrodes resembles that of the cylindrical ion trap. The trapped ion population for ions created by electron impact exhibits linear growth against a first-order loss that has a time constant of about 50 µs; no ion loss occurs when the electron beam is off. The observed value of q z at low-mass cutoff for rf ion storage is -0.84. Pulsed extraction of all ions is accomplished by switching the trap electrodes from rf to voltages required to provide a linear dc extraction field. The TOF flight path includes a wide energy range reflectron. Better than unit mass resolution is achieved through m/z 500 without collisional ion cooling. With an extraction rate of 1 kHz and a recording rate of 4 spectra per second, a linear working curve is obtained between 36 pg and 18 ng of chlorobenzene delivered chromatographically. The system has demonstrated the potential to achieve a very high sample utilization efficiency at high spectral generation rates.

Design and performance of an atmospheric pressure sampling interface for ion-trap/time-of-flight mass spectrometry

“…An optimized extraction is typically achieved at rf amplitude phase angles between 90°-140°according to literature. 28,30,52 Channel B, delayed with respect to channel A of the PDG, was used to trigger the EI ionization gate. The PDG's channel C, again delayed with respect to channel B, was used to trigger the gate valve controller to control pulsed gas introduction.…”

“…Iontrap/TOF devices are an excellent match 16 and have been successfully used in combination with different ionization methods such as ESI, 18,20,21 MALDI, 18,22,23 glow discharge, 24 photoionization, [25][26][27] and EI/CI. [28][29][30] Also, studies of neutral volatile substances such as halocarbon compounds in air were performed using ion-trap/TOF devices. 28,[30][31][32][33][34][35] The innovation of the instrument presented here is the ability to analyze not only volatile but also nonvolatile neutrals sampled at atmospheric conditions.…”

“…[28][29][30] Also, studies of neutral volatile substances such as halocarbon compounds in air were performed using ion-trap/TOF devices. 28,[30][31][32][33][34][35] The innovation of the instrument presented here is the ability to analyze not only volatile but also nonvolatile neutrals sampled at atmospheric conditions. This article describes the design and performance of an ion-trap/linear time-of-flight mass spectrometer in which analyte originating either from laser ablation or from volatile compounds are sampled by a home-built atmospheric pressure direct-sampling interface.…”

Characterization of a hybrid ion trap

“…There are several reasons to deviate from the standard geometry, such as increased ion storage [1], rapid ion extraction [2], prolonged ion storage [3], miniaturization [4], and ease of machining [5]. We consider here a different geometry with which to study the effect of ring electrode geometry on the performance of ion trap operation.…”

“…There have been a variety of radio-frequency ion traps that do not conform to the standard hyperbolic geometry described in the literature [1][2][3][4][5][6][7][8][9][10][11]. There are several reasons to deviate from the standard geometry, such as increased ion storage [1], rapid ion extraction [2], prolonged ion storage [3], miniaturization [4], and ease of machining [5].…”