Development and Characterization of a Field-Deployable Ion-Trap Mass Spectrometer with an Atmospheric Pressure Interface

Abstract

A field-deployable quadrupole ion-trap mass spectrometer with an atmospheric pressure interface is designed, built, and characterized. The instrument enclosure (48 cm × 43 cm × 42 cm) includes a roughing pump and a helium lecture bottle; the total weight of the instrument is 68 kg. Peak power consumption during the instrument operation is ∼500 W. The instrument has a mass range of m/z 30-2500, across which it provides better than unit mass resolution. The typical peak width at half height is 0.3 Th for a scan speed of 4000 Th/s. Operation of the instrument with electrospray and atmospheric-pressure matrix-assisted laser desorption ionization (AP-MALDI) ion sources is demonstrated. AP-MALDI analysis of low femtomole amounts of peptides reveals that the sensitivity of the instrument is on par with modern commercially available quadrupole ion-trap mass spectrometers. Tandem mass spectrometry capabilities of the instrument include simultaneous isolation and fragmentation of several different compounds. Two ways to reduce the size, weight, and power consumption of the portable instrument were explored, and results of these initial studies are presented. One of the ways includes utilization of hydrogen as a buffer gas for operation of the ion-trap mass analyzer in combination with a metal hydride method for storage of hydrogen in a compact rechargeable cartridge. Furthermore, careful selection of the inlet capillary dimensions allowed to eliminate the first "1 Torr" stage of the differential pumping without any significant loss of the instrument sensitivity. The elimination of this first pumping stage removed two turbo drag pumps, which substantially decreased the instrument's maximum power consumption (to ∼300 W in peak use, and ∼150 W during standby), as well as its size (to 30 cm × 43 cm × 50 cm) and weight (to 35 kg).

Development of a miniature mass spectrometer with continuous atmospheric pressure interface

“…31 Generally speaking, two types of miniature mass spectrometers have been developed on a system level up to now: 1) miniature mass spectrometers with continuous gas inlets and internal ionization sources, [32][33][34][35][36][37] which could only analyze 4 gas or volatile samples. 45,46 2) Miniature mass spectrometers with a discontinuous atmospheric pressure interface (DAPI), [47][48][49] which can work with ionization sources in ambient environment. Although ion transfer could be achieved by increasing the gas flow rate and by utilizing much larger and powerful vacuum pumps, the size and power consumption of the MS instrument will suffer correspondingly.…”

“…Although ion transfer could be achieved by increasing the gas flow rate and by utilizing much larger and powerful vacuum pumps, the size and power consumption of the MS instrument will suffer correspondingly. 45,46 (2) Miniature mass spectrometers with a discontinuous atmospheric pressure interface (DAPI), [47][48][49] which can work with ionization sources in an ambient environment. In a DAPI setup, high gas flow rate and efficient ion transfer are realized by mechanically opening the API for a very short duration (on the scale of milli-seconds).…”

Numerical Modeling of Ion Transport in an ESI-MS System

“…All solutions and peptide were purchased from Sigma (Sigma-Aldrich, St. Louis, MO, USA). The ion current measurements were performed using a prototype unit similar to the one used in a portable mass spectrometer 16 . The MS inlet was a glass-lined stainless steel capillary (0.5 mm i.d, 1.6 mm o.d., 10 cm long) from SIS (Ringoes, NJ) with its head (2 cm long) embedded in a massive copper block.…”

“…The DSMC method is used in this work to model the ion transport in a carrier gas flow expanding through a long capillary into a low-pressure background gas before passing through a skimmer into the hexapole chamber. The main objective of the work is to analyze the efficiency of the traditional capillary/Einzel lens/off-center skimmer approach, currently used in portable mass spectrometers 16 , and study the effect of changing voltage at the Einzel (tube) lens. The companion experimental study provides not only the actual geometric and flow properties of interest, but also solid ground for model validation.…”

ChiMS: Open-source instrument control software platform on LabVIEW for imaging/depth profiling mass spectrometers

“…Briefly, a laser front end was designed for a customized ion source coupled to a field deployable mass spectrometer with an atmospheric pressure interface (MTE50, MassTech). 25 The laser front end includes a motion stage with controller (ESP300, Newport) and a low cost multifunctional data acquisition device (Analog Discovery, Digilent) connected to an energy meter (J4-09, Molectron) for laser pulse energy measurement. ChiMS is used in this alternate setup for laser beam profiling and also sample rastering by the motion stage, with the acquisition of mass spectra handled by the software provided by the mass spectrometer vendor.…”