Pulsed Nano-ESI Atmospheric-Pressure Ion Mobility Mass Spectrometry with Enhanced Ion Sampling

Abstract

Ion mobility-mass spectrometry (IM-MS) has gained considerable attention for detection of clusters and weakly bound species created by electrospray ionization (ESI). Atmospheric-pressure (AP) IM-MS offers an advantage in these studies compared to its low-pressure counterpart, owing to soft introduction of ions into the mobility cell with minimal ion activation. Here, we report new approaches to improve the sensitivity and soft ion introduction in AP-IM-MS. For the former, we demonstrate enhanced aerodynamic sampling of ions from the mobility cell into the MS using pulsed-field sampling. In this approach, ions are driven toward the MS, and the field is shut down once the ions reach the vicinity of the MS inlet orifice. The pulsed-field operation provides arrival times without the need for an exit ion gate in the mobility cell and leads to improvements in sensitivity of up to 1 order of magnitude. For soft ion generation, we report a pulsed nano-ESI source to introduce a packet of ions into the room-temperature mobility cell without induced desolvation. Further, we demonstrate the application of the pulsed nano-ESI AP-IM-MS with enhanced ion sampling for detection of solvent clusters of amines and peptide aggregates.

Rapid detection of sulfur mustard hydrolysis products based on microextraction by packed sorbent combined with nano‐electrospray ionization mass spectrometry

“…Stadlmair et al 17 used nano‐ESI to detect the degradation products of different enzymes in water. McMahon et al 18,19 combined pulsed nano‐ESI with ion mobility mass spectrometry to improve the efficiency of ion acquisition. Microextraction by packed sorbent (MEPS) 20,21 is one of the fastest developed microextraction sample processing technologies.…”

Pulsed Nano-ESI: Application in Ion Mobility-MS and Insights into Spray Dynamics

“…Low duty cycles in AP drift tubes, however, lead to reduced sensitivity and low sample utilization efficiency. Multiplexing methodologies have been developed to improve sensitivity. − In parallel, we have explored a different strategy using pulsed nano-ESI for ion introduction into the IM cell . In this approach, the pulsed spray replaces the entrance gate of the IM cell and serves as both the ion source and ion injection method.…”

Perturbation-induced high-frequency pulsing of nano-ESI with facile ion selection at atmospheric pressure

“…Various pulsing schemes have been utilized such as a piezoelectric-assisted pulsing, 6 induced pulsing through a dielectric, [7][8][9] pulsing the potential supplied to the solution, [10][11][12][13] and pulsing the electric field in the proximity of the emitter. 14,15 Practical and fundamental advantages have been demonstrated for pulsed nano-ESI relative to continuous operation. For example, several studies have shown reduced sample consumption in pulsed mode relative to continuous operation.…”

“…12 Controlled pulsing of nano-ESI and short ion bursts also enable the direct use of this ionization mode for introducing discrete packets of ions into drift tubes utilized in atmospheric-pressure (AP) ion mobility separations. 14,15 In a recent study using this approach, we investigated the effect of nano-ESI pulse duration on ionization, demonstrating that long pulse duration preferentially enhanced the intensity of low-ionization-efficiency analytes, while the collision cross sections did not change appreciably. These studies indicated a temporal evolution of droplet sizes during a pulsed spray and suggested that final ion structures emerge rapidly with minimal impact of pulse duration on the measured collision cross section.…”

“…Our previous investigations using pulsed nano-ESI with AP mobility separations utilized relatively low frequencies (20)(21)(22)(23)(24)(25), limiting the ion flux. 14,15 Herein we present a new approach for pulsing nano-ESI coupled with ion selection operated at high repetition rates (500-3800 Hz) to increase the ion flux. The approach is based on a simplified instrumental setup consisting of a nano-ESI and a single pulsing ion gate that perturbs nano-ESI operation at high frequencies, resulting in pulsation of the spray.…”