Plasma‐based ambient mass spectrometry techniques: The current status and future prospective

Abstract

Plasma-based ambient mass spectrometry is emerging as a frontier technology for direct analysis of sample that employs low-energy plasma as the ionization reagent. The versatile sources of ambient mass spectrometry (MS) can be classified according to the plasma formation approaches; namely, corona discharge, glow discharge, dielectric barrier discharge, and microwave-induced discharge. These techniques allow pretreatment-free detection of samples, ranging from biological materials (e.g., flies, bacteria, plants, tissues, peptides, metabolites, and lipids) to pharmaceuticals, food-stuffs, polymers, chemical warfare reagents, and daily-use chemicals. In most cases, plasma-based ambient MS performs well as a qualitative tool and as an analyzer for semi-quantitation. Herein, we provide an overview of the key concepts, mechanisms, and applications of plasma-based ambient MS techniques, and discuss the challenges and outlook.

Investigation and Applications of In-Source Oxidation in Liquid Sampling-Atmospheric Pressure Afterglow Microplasma Ionization (LS-APAG) Source

“…ESI is widely used to ionize polar analytes in a broad mass range to provide MW information; thus when high DC voltage was applied to the syringe needle, and the polar analytes in the solution were ionized via ESI mechanism. In APAG mode, the analyte droplets formed at the capillary tip would produce gaseous molecules through thermal-assisted or gas-driven solvent evaporation, and then these gaseous molecules were ionized in the afterglow region via APAG mechanism similar to that occurring in the atmospheric pressure chemical ionization (APCI) source [13][14][15]. This APAG mode is more suitable for thermostable, weakly polar or nonpolar small molecules.…”

“…In recent years, numerous plasma-based ionization techniques under atmospheric pressure or ambient conditions [13][14][15][16][17] are emerging as powerful tools for rapid analysis of diverse analytes, which can also employ Breactive^plasma as the ionization reagent to initiate various types of reactions [18][19][20][21], including conventional chemical reactions, electrochemical or photochemical reactions, and gas-phase ion-molecule reactions. In-source oxidation, as a common reaction in the ionization process, should be avoided in routine analysis but has been successfully applied in structural analysis [7].…”

Direct Analysis of Amphetamine Stimulants in a Whole Urine Sample by Atmospheric Solids Analysis Probe Tandem Mass Spectrometry

“…An APCI-like process promotes sample ionization in the gas phase, where the corona discharge needle produces a plasma that ionizes the analytes and generates protonated molecules in the presence of water or radical ions in dry conditions [7]. A significant advantage of ASAP-MS is that introduction of the sample into the mass spectrometer ion source dismisses the need for a vacuum lock or an interface with HPLC [6]. Moreover, the analytes can be ionized under open-air and then directly and rapidly analyzed with high throughput and minimal simple pretreatment [8].…”

“…In the last decade, one of the most important advances in the field of mass spectrometry was the development of ambient mass spectrometry (AMS) techniques, such as desorption electrospray ionization (DESI), direct analysis in real time (DART), easy ambient sonic spray ionization (EASI), and atmospheric solids analysis probe mass spectrometry (ASAP) [6]. In ASAP-MS, the operator simply dips the end of the sealed glass capillary into the solid sample or solution, to coat the outside of the capillary with the sample.…”

Regulated In Situ Generation of Molecular Ions or Protonated Molecules under Atmospheric-Pressure Helium-Plasma-Ionization Mass Spectrometric Conditions

“…For DART and other atmospheric pressure chemical ionization (APCI) methods, a glow or corona discharge is deployed. Although abundant ion formation occurs when analytes are exposed to discharges, the overall mechanism of ionization remains poorly defined [5][6][7][8][9][10][11][12][13], and the need to understand it has been duly recognized [14,15]. It is agreed that a complex cascade of gas-phase interactions take place before the target molecules are eventually charged [15,16].…”