Online Simultaneous Hydrogen/Deuterium Exchange of Multitarget Gas-Phase Molecules by Electrospray Ionization Mass Spectrometry Coupled with Gas Chromatography

Abstract

In this study, a hydrogen/deuterium (H/D) exchange method using gas chromatography-electrospray ionization/mass spectrometry (GC-ESI/MS) was first investigated as a novel tool for online H/D exchange of multitarget analytes. The GC and ESI source were combined with a homemade heated column transfer line. GC-ESI/MS-based H/D exchange occurs in an atmospheric pressure ion source as a result of reacting the gas-phase analyte eluted from GC with charged droplets of deuterium oxide infused as the ESI spray solvent. The consumption of the deuterated solvent at a flow rate of 2 μL min was more economical than that in online H/D exchange methods reported to date. In-ESI-source H/D exchange by GC-ESI/MS was applied to 11 stimulants with secondary amino or hydroxyl groups. After H/D exchange, the spectra of the stimulants showed unexchanged, partially exchanged, and fully exchanged ions showing various degrees of exchange. The relative abundances corrected for naturally occurring isotopes of the fully exchanged ions of stimulants, except for etamivan, were in the range 24.3-85.5%. Methylephedrine and cyclazodone showed low H/D exchange efficiency under acidic, neutral, and basic spray solvent conditions and nonexchange for etamivan with an acidic phenolic OH group. The in-ESI-source H/D exchange efficiency by GC-ESI/MS was sufficient to determine the number of hydrogen by elucidation of fragmentation from the spectrum. Therefore, this online H/D exchange technique using GC-ESI/MS has potential as an alternative method for simultaneous H/D exchange of multitarget analytes.

Vibrating Sharp‐edge Spray Ionization (VSSI) for voltage‐free direct analysis of samples using mass spectrometry

“…In addition to the diversity of suitable target molecules accessed by VSSI, another attractive feature of VSSI is the capability to operate multiple sources simultaneously. Such an approach would allow the probing of fast chemical processes by mixing the contents of different droplets within the ion source region 38–41 . Compared with ESI‐based spray, the zero‐voltage characteristics of VSSI makes it convenient to operate multiple sources close to each other without worrying about the potential of electrical breakdown (in the case of opposite polarity needles) or problems of greater nanodroplet repulsion (in the case of similar polarity needles).…”

Hydrogen/Deuterium Exchange Aiding Compound Identification for LC-MS and MALDI Imaging Lipidomics

“…The use of gas-phase H/D exchange for the investigation of the gaseous conformations of proteins was also demonstrated . Recently, it was demonstrated that HDX could be coupled to the GC-ESI-MS systems and IMS systems . It was also shown that hydrogen/deuterium exchange can be performed in the gas phase at atmospheric pressure − and low or high vacuum conditions.…”

Ionization of Gas-Phase Polycyclic Aromatic Hydrocarbons in Electrospray Ionization Coupled with Gas Chromatography

“…To overcome this limitation related to the ionization issue, tropylium derivatization 26 or silver coordination 35−37 Recently, GC/ESI-MS/MS, combining both the excellent chromatographic resolving power of GC and the soft ionization of ESI, has been reported. 39,41 GC/ESI-MS, which was implemented by simply interfacing GC with ESI-MS, was first demonstrated in 2008 by Brenner et al 39 In GC/ESI-MS, analyte ions are speculated to be formed either by the instantaneous dissolution of a gas-phase analyte eluted by GC into an ESI solvent droplet or by the gas-phase reaction of analytes eluted by GC with electrosprayed solvent molecules. 42 Our group has also shown that steroids, such as trimethylsilyl derivatives, could be analyzed using GC/ESI-MS with a high separation efficiency and enhanced selectivity/sensitivity.…”