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

A field-deployable quadrupole ion-trap mass spectrometer with an atmospheric pressure interface is designed, built, and characterized. The instrument enclosure (48 cm x 43 cm X 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 similar to 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 similar to 300 W in peak use, and similar to 150 W during standby), as well as its size (to 30 cm x 43 cm x 50 cm) and weight (to 35 kg).