Sensitive Monitoring of Volatile Chemical Warfare Agents in Air by Atmospheric Pressure Chemical Ionization Mass Spectrometry with Counter-Flow Introduction

Abstract

A new method for sensitively and selectively detecting chemical warfare agents (CWAs) in air was developed using counter-flow introduction atmospheric pressure chemical ionization mass spectrometry (MS). Four volatile and highly toxic CWAs were examined, including the nerve gases sarin and tabun, and the blister agents mustard gas (HD) and Lewisite 1 (L1). Soft ionization was performed using corona discharge to form reactant ions, and the ions were sent in the direction opposite to the airflow by an electric field to eliminate the interfering neutral molecules such as ozone and nitrogen oxide. This resulted in efficient ionization of the target CWAs, especially in the negative ionization mode. Quadrupole MS (QMS) and ion trap tandem MS (ITMS) instruments were developed and investigated, which were movable on the building floor. For sarin, tabun, and HD, the protonated molecular ions and their fragment ions were observed in the positive ion mode. For L1, the chloride adduct ions of L1 hydrolysis products were observed in negative ion mode. The limit of detection (LOD) values in real-time or for a 1 s measurement monitoring the characteristic ions were between 1 and 8 μg/m(3) in QMS instrument. Collision-induced fragmentation patterns for the CWAs were observed in an ITMS instrument, and optimized combinations of the parent and daughter ion pairs were selected to achieve real-time detection with LOD values of around 1 μg/m(3). This is a first demonstration of sensitive and specific real-time detection of both positively and negatively ionizable CWAs by MS instruments used for field monitoring.

On-Site Detection of Chemical Warfare Agents

“…Adopting an ion-trap mass analyzer (MS n function), many types of nerve gases, blistering agents, vomiting agents, and lachrymators are detected within several seconds with the LOD in the sub-μg/m 3 area (Seto et al, 2013) (DS-1000, Figure 60.7). The monitoring tape method (Nakano and Nagashima, 2001) detects hazardous gases by spectrophotometrically measuring the color change on the tape or tab impregnated with specific reagents after reacting with the suctioned air sample (Figure 60.8).…”

In-Line Ozonation for Sensitive Air-Monitoring of a Mustard-Gas Simulant by Atmospheric Pressure Chemical Ionization Mass Spectrometry

“…A quadrupole ion trap was used for MS n analysis. The variable temperatures of the instrument's sampling tube, ionization chamber, and ion inlet into the vacuum system were set at 120°C (which is the same as those set in previous studies [18,19,26]). …”

“…Ion-trap mass analyzers, which are capable of MS n , are suitable for field use because of their compactness and robustness. Atmospheric pressure chemical ionization (APCI) ion-trap MS n with a counter-flow ion introduction (CFI) [17] configuration provides sufficient sensitivity for hygiene management of a wide range of CWAs [18,19]. Mustard gas [bis(2-chloroethyl) sulfide, HD] is one of the common CWAs.…”

“…In the case of CFI-APCI-MS n [18,19], HD is efficiently protonated so that it can provide dominant mass-spectral ion peaks under low humidity. However, as air humidity increases, the peak intensities sharply decrease owing to interference of protonation by moisture and fall below those of the protonated monooxygenated HD.…”

Detection of chemical warfare agent simulants and hydrolysis products in biological samples by paper spray mass spectrometry

“…[9][10][11][12][13] Many of the fielded MS methods require the use of gas chromatography (GC) and/or liquid chromatography (LC), which pose difficulties for rapid analysis due to sample preparation needs 14 and lengthy run times. Several rapid, on-site methods have been proposed, such as atmospheric pressure chemical ionization (APCI) MS, 15,16 selected ion flow tube (SIFT) MS, 17,18 and proton transfer reaction (PTR) MS. 19 However, these methods can only measure a limited range of volatile small molecules and have strong carry-over between runs, which decreases the rate of sample analysis. Direct analysis in real time (DART) MS, an ambient ionization method, has been shown to successfully analyze (and quantitate) CWAs 20 and explosives.…”