Arc-Induced Nitrate Reagent Ion for Analysis of Trace Explosives on Surfaces Using Atmospheric Pressure Arc Desorption/Ionization Mass Spectrometry

Abstract

This study presents the rapid surface detection of explosives by employing atmospheric pressure arc desorption/ionization mass spectrometry (APADI-MS) using point-to-plane arc discharge. In APADI, neutral explosives readily bind to the gas-phase nitrate ion, NO3 –, induced by arc discharge to form anionic adducts [M+NO3]−. This avoids the need for inorganic anionic additives such as NO3 –, NO2 –, Cl–, acetate, and trifluoroacetate for unique explosive ionization pathways and simplifies mass spectra. The analytical performance of APADI was thoroughly evaluated for the rapid detection of 10 explosives at levels in the range of 800 fg–1 μg. Arc-induced nitrogen oxide anions promoted the formation of characteristic adducts, such as [M+NO3]−, and improved the instrument response for all the explosives tested. APADI showed considerable sensitivity in the negative ion mode with limits of detection in the low picogram range, particularly when explosives were analyzed on a copper or aluminum foil substrate. APADI coupled with an Orbitrap mass spectrometer displayed a good linear response for the studied explosives. The linearity and intraday and interday precisions were evaluated, demonstrating the feasibility and robustness of APADI-MS for the detection of trace explosives on solid surfaces. The mechanisms of APADI for explosive ionization and desorption were examined and verified by performing density functional theory calculations.

Arc-Induced Electrospray Ionization Mass Spectrometry

“…Except for OH•, AESI enhanced the positive ion species from the arc plasma, such as N 2 + ( m / z 28.4), O 2 + ( m / z 32.3), NO 2 + ( m / z 46.4), O 2 H 2 O + ( m / z 50.4), O 4 + ( m / z 64.4), and [H 2 O] 3 H + ( m / z 54.6) (Figure E). When the arc ionizes the air, several negative ions are produced, including O 2 – , CO 4 – , CO 3 – , OH – , HCO 3 – , O 3 – , NO 2 – , and the cluster ion [HNO 3 + NO 3 ] − . Subject to CID, the H 4 O 2 +• ion displayed fragmentation behavior, and an H 3 O + fragment at m / z 19.0 was identified (Figure F), providing further evidence of the presence of OH•.…”

“…Plasma discharge techniques, such as corona discharge, dielectric barrier discharge, microwave-induced discharge, glow discharge, and arc discharge, − offer direct means of sample ionization. Applying plasma to ESI enhances ionization efficiency, provides instant detection, and heightens sensitivity compared to other ESI techniques .…”

“…In this study, we introduce arc-induced electrospray ionization (AESI) technology, which leverages the abundant charges and desorption temperature enabled by the AC arc. − Thermal effects facilitate microdroplet generation by transferring heat and electrons to the hollow metal probe, and charges generated by the arc and dispersed in microdroplets efficiently ionize the dissolved target analytes. AESI generates microdroplet aerosols, enabling microdroplet production.…”

A substituent-dependent deep-blue pyrene-based chemosensor for trace nitroaniline sensing

“…[4][5][6][7] In this context, a variety of methods have been established for explosives detection with a fast response time, super-sensitivity and ultra-selectivity, such as Raman spectroscopy, thermal neutron analysis, gas chromatography-electron capture detection and ion mobility spectroscopy. [8][9][10][11] However, traditional methods expose significant disadvantages, including long time-dependence for recognition, complexity of sample preparation and high cost. Given the urgency of the portability and sensitivity for detection, fluorescence detection of nitro-explosives by exploring the luminescence properties of luminogens has been widely investigated, including luminescent nitrogen-doped graphene quantum dots, 12 metal cluster decorated graphene nanoflakes, 1,[13][14][15] metal organic frameworks, 16,17 covalent organic frameworks and conjugated polymers.…”

Applications of ambient ionization mass spectrometry in 2022: An annual review

“…Gao et al developed an atmospheric pressure arc desorption/ionization MS (APADI-MS) technique for the analysis of 10 types of explosives 48. In APADI-MS, the sample is simply placed on a copper substrate over which a needle is positioned.…”