Combined atomic and molecular (CAM) ionization with the liquid sampling‐atmospheric pressure glow discharge microplasma

Abstract

In a world where information‐rich methods of analysis are often sought over those with superior figures of merit, there is a constant search for ionization methods which can be applied across diverse analytical systems. The liquid sampling‐atmospheric pressure glow discharge (LS‐APGD) is a microplasma device which has the inherent capabilities to operate as a combined atomic and molecular (CAM) ionization source. The plasma is sustained by placement of a high voltage (~500 V, dc) onto an electrolytic solution through which the analyte is generally delivered to the discharge. Judicious choice of the solvent provides a means of obtaining atomic/elemental and/or molecular mass spectra. Presented here are the diverse modes of sample introduction and mass spectrometer platforms to which the LS‐APGD has been interfaced. Likewise, representative spectra and figures of merit are presented towards elemental and isotope ratio measurements, as well as application to small organic molecules, organometallic complexes, and intact proteins. It is believed that the diversity of analytical applications and ready implementation across the entirety of mass spectrometry platforms portends a level of versatility not realized with other ionization sources.

Initial Characterization and Optimization of the Liquid Sampling-Atmospheric Pressure Glow Discharge Ionization Source Coupled to an Orbitrap Mass Spectrometer for the Determination of Plutonium

“…Characterization of Ionized Pu-Species and Utilization of Collisional Dissociation Modalities. While the CAM ionization capabilities of the microplasma are powerful in understanding solution phase chemistries, 23,29,41 the use of the LS-APGD in an elemental/isotopic mode requires that analyte-containing species be broken down to their simplest form to achieve high sensitivity and reduce influences of solution chemistry. Solvent-related species, both analyte and background, are frequently encountered with solution-based atmospheric pressure plasma sources.…”

“…A dual-electrode LS-APGD ionization source was coupled to the Orbitrap mass spectrometer, as described previously , and presented diagrammatically in Figure . This source has demonstrated superior sensitivity over the single-electrode mode, as illustrated in Supporting Information (SI) Figure S1.…”

“…While initially envisioned as an ionization source for elemental analysis, expanded studies have demonstrated the versatility of the LS-APGD. Indeed, the LS-APGD is a combined atomic and molecular (CAM) source that has proven to be able to analyze small polar/nonpolar molecules and proteins. − …”

Atomic spectrometry update: review of advances in atomic spectrometry and related techniques

“…Solvent selection provides the means of obtaining atomic/elemental and/or molecular mass spectra. Marcus et al 46 provided an overview of the varied modes of sample introduction and MS platforms to which the LS-AP-GD has been interfaced. Representative spectra and analytical figures of merit for elemental and IR measurements were presented, in addition to descriptions of the application to small organic molecules, organometallic complexes, and intact proteins.…”

Shake It Off! Acoustic Manipulation of Lipid Vesicles for Mass Spectrometric Analysis

“…Finally, we had incidentally observed that the SAWN-APCI method demonstrated capability for small protein ionization under native conditions as similar techniques have previously. 28 In Figure 7A, we show the mass spectrum of sampled droplets containing 14 kDa cytochrome C and spiked DOPC lipid with formal concentrations of 12.5 and 25 μM, respectively, observed by SAWN-APCI alone. In Figure 7B, the cytochrome C is spiked into the DOPC liposome solution (not incorporated into the liposomes themselves), which is then subjected to 40 s of 64 MHz SAWs prior to SAWN-APCI.…”