Catalyst-Free Oxidation Reactions in a Microwave Plasma Torch-Based Ion/Molecular Reactor: An Approach for Predicting the Atmospheric Oxidation of Pollutants

Abstract

The atmospheric oxidation of chemicals has produced many new unpredicted pollutants. A microwave plasma torch-based ion/molecular reactor (MPTIR) interfacing an online mass spectrometer has been developed for creating and monitoring rapid oxidation reactions. Oxygen in the air is activated by the plasma into highly reactive oxygen radicals, thereby achieving oxidation of thioethers, alcohols, and various environmental pollutants on a millisecond scale without the addition of external oxidants or catalysts (6 orders of magnitude faster than bulk). The direct and real-time oxidation products of polycyclic aromatic hydrocarbons and p-phenylenediamines from the MPTIR match those of the long-term multistep environmental oxidative process. Meanwhile, two unreported environmental compounds were identified with an MPTIR and measured in the actual water samples, which demonstrates the considerable significance of the proposed device for both predicting the environmental pollutants (non-target screening) and studying the mechanism of atmospheric oxidative processes.

Nonderivatized Method for the Detection of Perfluoroalkane Sulfonyl Fluorides by Liquid Chromatography–Microwave Plasma Torch Ionization Mass Spectrometry

“…In our previous work, it was demonstrated that microwave plasma can rapidly catalyze the oxidation of some environmental pollutants with simultaneous ionization of the analyte . PFASFs could be converted to PFSAs online in an ambient MPTI source and detected in the negative ion mode of high-resolution mass spectrometry (Figure a).…”

“…Argon was introduced as the working gas through the middle and inner tubes and controlled by a rotameter, which could be adjusted within the range of 500–2000 mL/min (typically 1000 mL/min). The input microwave frequency was 2.45 GHz, and the power could be adjusted from 0 to 200 W. During operation, a bright purple columnar plasma beam was generated between the middle tube and the inner tube . The mass spectrometry inlet ESI source was unloaded to create an open ion transfer inlet.…”

“…GHz, and the power could be adjusted from 0 to 200 W. During operation, a bright purple columnar plasma beam was generated between the middle tube and the inner tube. 26 The mass spectrometry inlet ESI source was unloaded to create an open ion transfer inlet. Chemicals and Reagents.…”

“…In recent years, its capabilities as an atmospheric pressure ion source have been explored, allowing desorption and ionization of analytes from surfaces for mass spectrometric analysis. , In comparison to traditional plasma ion sources, MPT demonstrates increased ion collision probabilities and energies, resulting in the production of significant quantities of primary reagent ions . Furthermore, our previous research discovered that in the operation of an atmospheric pressure plasma ion source device, plasma-activated oxygen and water in the air will produce a large number of reactive oxygen fragments and hydroxyl radicals, which can quickly carry out the oxidation of some compounds. On this basis, we propose a liquid chromatography-microwave plasma torch ionization-mass spectrometry (LC-MPTI-MS) technique for the rapid conversion of PFASFs to perfluoroalkanesulfonic acids (PFSAs) by reactive oxygen species and hydroxyl radicals within the microwave plasma, resulting in the online mass spectrometric detection of PFASFs in negative ion mode.…”

Dual Tunability for Uncatalyzed N‐Alkylation of Primary Amines Enabled by Plasma‐Microdroplet Fusion

“…Indeed, plasma‐over‐liquid platforms utilizing liquid absorbents have shown significantly improved yield [9] with applications in nanoparticle synthesis, [10a] in which liquid absorbent acts to sequester and protect products formed in the gas phase. Pollutant oxidation has also been achieved by spraying the sample into a microwave plasma torch [10b] . Additionally, charged microdroplets produced via electrospray have shown remarkable results in both reaction acceleration [11] and preparative scale‐up [12] .…”