Selectivity of Explosives Analysis with Ambient Ionization Single Quadrupole Mass Spectrometry: Implications for Trace Detection

Abstract

Ambient ionization (AI) is a rapidly growing field in mass spectrometry (MS). It allows for the direct analysis of samples without any sample preparation, making it a promising technique for the detection of explosives. Previous studies have shown that AI can be used to detect a variety of explosives, but the exact gas-phase reactions that occur during ionization are not fully understood. This is further complicated by differences in mass spectrometers and individual experimental set ups between researchers. This study investigated the gas-phase ion reactions of five different explosives using a variety of AI techniques coupled to a Waters QDa mass spectrometer to identify selective ions for explosive detection and identification based on the applied ambient ionization technique. The results showed that the choice of the ion source can have a significant impact on the number of ions observed. This can affect the sensitivity and selectivity of the data produced. The findings of this study provide new insights into the gas-phase ion reactions of explosives and could lead to the development of more sensitive and selective AI-based methods for their detection.

In-line Thermal Desorption and Dielectric Barrier Discharge Ionization for Rapid Mass Spectrometry Detection of Explosives

“…At the low mass loadings investigated, no significant dimer peaks (or other peaks) in the high(er) ion mass range (i.e., m/z >400) were observed, therefore displayed spectra were generally truncated at m/z 400. The only deviation from nitrate adducts was observed for the nitroaromatic TNT, where the common loss of -NO was observed (m/z 197 [TNT-NO] -) and adduct (m/z 260 [TNT+OOH] -) previously observed with DART and APCI 18,28 (Figure 1(c)). Interestingly, Tetryl also yielded predominantly the nitrate adduct (m/z 349 [Tetryl+NO3] -), with minor peaks for the loss of NO and NO2 (Figure S1).…”

“…Previous works with related plasma-based sources such as DART, confined DART, ASAP, and TDCD exhibited the m/z 241 [Tetrly-NO2] -(N-methyl-2,4,6 trinitroaniline fragment ion) as the dominant observed ion. 18,29,30 Ion distributions were also briefly investigated on an alternative mass analyzer (JEOL AccuTOF time-of-flight) to gauge ion source vs mass analyzer effects (Figure S2). There was very little difference observed for most of the explosives investigated.…”

“…Originating in the early 2000s with the advent of direct analysis in real time (DART) 11 and desorption electrospray ionization (DESI), 12 ambient ionization approaches have expanded extensively 13,14 and been applied to countless applications, including forensics 15,16 and explosives detection. 17,18 Recent studies have focused on comparing multiple ambient ionization platforms all on a single mass spectrometer, including atmospheric pressure chemical ionization (APCI), DESI, paperspray ionization (PSI), papercone spray ionization (PCSI), and electrospray ionization (ESI) on a cylindrical ion trap for forensic evidence screening; 16 and ESI, PSI, atmospheric solids analysis probe (ASAP), thermal desorption corona discharge (TDCD), and DART on a single quadrupole for explosives detection. 18 In this Technical Note, we employ a multimode ambient ionization coupling that enabled rapid chromatography-free analysis of organic explosive, propellant, and post-blast debris mass spectrometry signatures.…”

“…17,18 Recent studies have focused on comparing multiple ambient ionization platforms all on a single mass spectrometer, including atmospheric pressure chemical ionization (APCI), DESI, paperspray ionization (PSI), papercone spray ionization (PCSI), and electrospray ionization (ESI) on a cylindrical ion trap for forensic evidence screening; 16 and ESI, PSI, atmospheric solids analysis probe (ASAP), thermal desorption corona discharge (TDCD), and DART on a single quadrupole for explosives detection. 18 In this Technical Note, we employ a multimode ambient ionization coupling that enabled rapid chromatography-free analysis of organic explosive, propellant, and post-blast debris mass spectrometry signatures. Thermal desorption (TD) of wipe-based (i.e., from swipe sample collection) and melting point capillary-based (i.e., from liquid extraction) sample introduction was connected in-line with a dielectric barrier discharge ionization (DBDI) source.…”

Crystallization and Solvent Evaporation Ionization Mass Spectrometry (CSEI-MS) for Rapid Detection of Drugs in Complex Matrices

“…Ambient mass spectrometry (AMS) is widely applied in many fields, especially in fingerprint analysis, detection of drugs, explosive residues, etc. due to its advantages of fast, easy operation, real time, and in situ analysis without complicated pretreatments. − Some techniques based on electrospray (ESI) were applied, such as surface-coated wooden-tip ESI for the determination of trace antibiotics in water. The modified iron sheet acted as spray tip for selective enrichment and desalting detection of sulfonamides. − These methods require modifications of the material for specific analytes and may, therefore, have some challenges for the detection of other analytes.…”