Development
of an Atmospheric Pressure Ion Mobility
Spectrometer–Mass Spectrometer with an Orthogonal Acceleration
Electrostatic Sector TOF Mass Analyzer
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Abstract
Recently
developed ion mobility mass spectrometer is described.
The instrument is based on a drift tube ion mobility spectrometer
and an orthogonal acceleration electrostatic sector time-of-flight
mass analyzer. Data collection is performed using a specially developed
fast ADC-based recorder that allows real-time data integration in
an interval between 3 and 100 s. Primary tests were done with positive
ion electrospray. The tests have shown obtaining 100 ion mobility
resolving power and 2000 mass resolving power. Obtained for 2,6-di-<i>tert</i>-butylpyridine in electrosprayed liquid samples during
100 s analysis and full IMS/MS data collection mode were 4 nM relative
limits of detection and a 1 pg absolute limit of detection (S/N=3).
Characteristic ion mobility/mass distributions were recorded for selected
antibiotics, including amoxicillin, ampicillin, lomefloxacin, and
ofloxacin. At studied conditions, lomefloxacin forms only a protonated
molecule-producing reduced ion mobility peak at 1.082 cm<sup>2</sup>/(V s). Both amoxicillin and ampicillin produce [M + H]<sup>+</sup>, [M + CH<sub>3</sub>OH + H]<sup>+</sup>, and [M + CH<sub>3</sub>CN + H]<sup>+</sup>. Amoxicillin shows two peaks at 0.909 cm<sup>2</sup>/(V s) and 0.905 cm<sup>2</sup>/(V s). Ampicillin shows one
peak at 0.945 cm<sup>2</sup>/(V s). Intensity of protonated methanol
containing cluster for both ampicillin and amoxicillin has a clear
tendency to rise with sample keeping time. Ofloxacin produces two
peaks in the ion mobility distribution. A lower ion mobility peak
at 1.051 cm<sup>2</sup>/(V s) is shown to be formed by [M + H]<sup>+</sup> ions. A higher ion mobility peak appearing for samples kept
more than 48 h is shown to be formed by both [M + H]<sup>+</sup> ion
and a component identified as the [M + 2H + M]<sup>+2</sup> cluster.
The cluster probably partly dissociates in the interface producing
the [M + H]<sup>+</sup> ion