[Sulzer2013a] "Applications of switching reagent ions in proton transfer reaction mass spectrometric instruments for the improved selectivity of explosive compounds",
International Journal of Mass Spectrometry
, vol. 354–355: Elsevier, 2013.
<p>Here we demonstrate the use of a switchable reagent ion proton transfer reaction mass spectrometry (SRI-PTR-MS) instrument to improve the instrument's selectivity for the detection of the explosive compounds 2,4,6 trinitrotoluene (TNT), 1,3,5 trinitrobenzene (TNB), pentaerythritol tetranitrate (PETN), and cyclotrimethylenetrinitramine (RDX). Selectivity is improved owing to the production of different product ions resulting from changes in the reagent ion-molecule chemistry. To be of use as an analytical tool for homeland security applications, it is important that the reagent ions (and hence product ions) can be rapidly changed (within seconds) from H3O+ to another dominant ion species if the technology is to be acceptable. This paper presents measurements that show how it is possible to rapidly switch the reagent ion from H3O+ to either O2+ or NO+ to enhance selectivity for the detection of the four explosives named above. That switching reagent ions can be done quickly results from the fact that the recombination energies of O2+ and NO+ are less than the ionisation potential of H2O, i.e. charge transfer cannot occur which otherwise would result in ions that can react efficiently with water (e.g. H2O+ + H2O → H3O+ + OH) leading to H3O+ becoming the dominant reagent ion. Reaction processes observed are non-dissociative charge transfer (O2+ with TNT and TNB), dissociative charge transfer (O2+ with TNT) and adduct formation (NO+ with PETN and RDX). O2+ is found to be unreactive with PETN and RDX, and under the conditions operating in the reaction region of the PTR-MS only a low signal associated with NO+·TNT was observed. No NO+·TNB was detected.</p>
[Lanza2013] "Distinguishing two isomeric mephedrone substitutes with selective reagent ionisation mass spectrometry (SRI-MS)",
Journal of Mass Spectrometry
, vol. 48, no. 9, pp. 1015–1018, 2013.
The isomers 4-methylethcathinone and N-ethylbuphedrone are substitutes for the recently banned drug mephedrone. We find that with conventional proton transfer reaction mass spectrometry (PTR-MS), it is not possible to distinguish between these two isomers, because essentially for both substances, only the protonated molecules are observed at a mass-to-charge ratio of 192 (C12H18NO+). However, when utilising an advanced PTR-MS instrument that allows us to switch the reagent ions (selective reagent ionisation) from H3O+ (which is commonly used in PTR-MS) to NO+, O2+ and Kr+, characteristic product (fragment) ions are detected: C4H10N+ (72 Da) for 4-methylethcathinone and C5H12N+ (86 Da) for N-ethylbuphedrone; thus, selective reagent ionisation MS proves to be a powerful tool for fast detection and identification of these compounds. Copyright © 2013 John Wiley & Sons, Ltd.
[Kassebacher2013] "Investigations of chemical warfare agents and toxic industrial compounds with proton-transfer-reaction mass spectrometry for a real-time threat monitoring scenario.",
Rapid Commun Mass Spectrom
, vol. 27, no. 2: Austria., pp. 325–332, Jan, 2013.
Security and protection against terrorist attacks are major issues in modern society. One especially challenging task is the monitoring and protection of air conditioning and heating systems of buildings against terrorist attacks with toxic chemicals. As existing technologies have low selectivity, long response times or insufficient sensitivity, there is a need for a novel approach such as we present here.We have analyzed various chemical warfare agents (CWAs) and/or toxic industrial compounds (TICs) and related compounds, namely phosgene, diphosgene, chloroacetone, chloroacetophenone, diisopropylaminoethanol, and triethyl phosphate, utilizing a high-resolution proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOFMS) instrument with the objective of finding key product ions and their intensities, which will allow a low-resolution quadrupole mass spectrometry based PTR-MS system to be used with high confidence in the assignment of threat agents in the atmosphere.We obtained high accuracy PTR-TOFMS mass spectra of the six compounds under study at two different values for the reduced electric field in the drift tube (E/N). From these data we have compiled a table containing product ions, and isotopic and E/N ratios for highly selective threat compound detection with a compact and cost-effective quadrupole-based PTR-MS instrument. Furthermore, using chloroacetophenone (tear gas), we demonstrated that this instrument's response is highly linear in the concentration range of typical Acute Exposure Guideline Levels (AEGLs).On the basis of the presented results it is possible to develop a compact and cost-effective PTR-QMS instrument that monitors air supply systems and triggers an alarm as soon as the presence of a threat agent is detected. We hope that this real-time surveillance device will help to seriously improve safety and security in environments vulnerable to terrorist attacks with toxic chemicals.
[Hartungen2013] "Proton transfer reaction-mass spectrometry: fundamentals, recent advances and applications",
The European Physical Journal Applied Physics
, vol. 61, no. 02: Cambridge Univ Press, pp. 24303, 2013.
Proton transfer reaction-mass spectrometry (PTR-MS) offers many advantages for trace gas analysis, including no sample preparation, real-time analysis, high selectivity and sensitivity, ultra-low detection limits and very short response times. These characteristic features have made it an ideal tool for many applications in science, technology and society. Here we will discuss recent developments, in particular advances concerning sensitivity, selectivity and general applicability.