Ryoji Sekioka

Detection performance of a portable ion mobility spectrometer with 63Ni radioactive ionization for chemical warfare agents

The detection performance of a portable ion mobility spectrometer (IMS) (SABRE 4000, Smiths Detection) with 63Ni ionization, air purification, and reduced ion mobility measurements using calibrants was investigated for vapors of chemical warfare agents. In a matter of several seconds, the SABRE 4000 enabled tentative identification of sarin, soman, cyclohexylsarin, tabun, and nitrogen mustard 3, each with a limit of alarm (LOA) of 0.005–0.5 mg m−3 in positive ion collection mode. Hydrogen cyanide could be identified with a LOA of 0.2 mg m−3 in the negative mode. Mustard gas, nitrogen mustards 1, 2, and 3, phosgene, and chloropicrin showed a positive alarm of “HD/Phos” with a LOA of 0.2–2 mg m−3 in negative mode. Lewisite 1, cyanogen chloride, and chlorine vapors did not show any alarm, although the characteristic ion peaks appeared in negative mode. The peak areas of the respective detected ions on the second differentiation spectra were positively correlated with the corresponding vapor concentrations in low concentration ranges. Several chemical agent simulants and organic solvents were also examined for detection by the machine. The SABRE 4000 is superior to other portable IMS machines at this time, although some improvements of the system are necessary.

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

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.

Sensitive and Comprehensive Detection of Chemical Warfare Agents in Air by Atmospheric Pressure Chemical Ionization Ion Trap Tandem Mass Spectrometry with Counterflow Introduction

A highly sensitive and specific real-time field-deployable detection technology, based on counterflow air introduction atmospheric pressure chemical ionization, has been developed for a wide range of chemical warfare agents (CWAs) comprising gaseous (two blood agents, three choking agents), volatile (six nerve gases and one precursor agent, five blister agents), and nonvolatile (three lachrymators, three vomiting agents) agents in air. The approach can afford effective chemical ionization, in both positive and negative ion modes, for ion trap multiple-stage mass spectrometry (MS(n)). The volatile and nonvolatile CWAs tested provided characteristic ions, which were fragmented into MS(3) product ions in positive and negative ion modes. Portions of the fragment ions were assigned by laboratory hybrid mass spectrometry (MS) composed of linear ion trap and high-resolution mass spectrometers. Gaseous agents were detected by MS or MS(2) in negative ion mode. The limits of detection for a 1 s measurement were typically at or below the microgram per cubic meter level except for chloropicrin (submilligram per cubic meter). Matrix effects by gasoline vapor resulted in minimal false-positive signals for all the CWAs and some signal suppression in the case of mustard gas. The moisture level did influence the measurement of the CWAs.

Real-Time Air Monitoring of Mustard Gas and Lewisite 1 by Detecting Their In-Line Reaction Products by Atmospheric Pressure Chemical Ionization Ion Trap Tandem Mass Spectrometry with Counterflow Ion Introduction

A new method enabling sensitive real-time air monitoring of highly reactive chemical warfare agents, namely, mustard gas (HD) and Lewisite 1 (L1), by detecting ions of their in-line reaction products instead of intact agents, is proposed. The method is based on corona discharge-initiated atmospheric pressure chemical ionization coupled with ion trap tandem mass spectrometry (MS(n)) via counterflow ion introduction. Therefore, it allows for highly sensitive and specific real-time detection of a broad range of airborne compounds. In-line chemical reactions, ionization reactions, and ion fragmentations of these agents were investigated. Mustard gas is oxygenated in small quantity by reactive oxygen species generated in the corona discharge. With increasing air humidity, the MS(2) signal intensity of protonated molecules of mono-oxygenated HD decreases but exceeds that of dominantly existing intact HD. This result can be explained in view of proton affinity. Lewisite 1 is hydrolyzed and oxidized. As the humidity increases from zero, the signal of the final product, namely, didechlorinated, dihydroxylated, and mono-oxygenated L1, quickly increases and reaches a plateau, giving the highest MS(2) and MS(3) signals among those of L1 and its reaction products. The addition of minimal moisture gives the highest signal intensity, even under low humidity. The method was demonstrated to provide sufficient analytical performance to meet the requirements concerning hygienic management and counter-terrorism. It will be the first practical method, in view of sensitivity and specificity, for real-time air monitoring of HD and L1 without sample pretreatment.

Detection of proteinous toxins using the Bio-Threat Alert system, part 3: effects of heat pretreatment and interfering substances

We previously reported that the Guardian Bio-Threat Alert (BTA) system could detect (detection limit: about 0.1 μg/ml) staphylococcal enterotoxin B (SEB), botulinum toxins (BTX) A and B, and ricin, with no interference by white-powdered materials or colored matrices. In this study, the capability of the BTA system was further assessed. With 10 min of preheating at 60°C, all toxins could be detected, but with preheating at 80°C, BTX A and B and ricin became undetectable. About 20% SEB could be detected after heating at 80°C, but this detection ability was completely removed after heating at 100°C. The effects of chemicals usually used for decontamination, such as sodium hypochlorite, hydrogen peroxide, formaldehyde, and sodium nitrite, on the detectability of SEB, BTX A, or ricin in the BTA system were also tested. The concentrations giving 50% line intensity for SEB, BTX A, and ricin were 3.1, 11, and 15 μM for sodium hypochlorite and 88, 210, and 60 mM for formaldehyde, respectively. The addition of hydrogen peroxide or sodium nitrite did not decrease the detectability even when used at high concentrations.

Detection of proteinous toxins using the Bio-Threat Alert system, part 4. Differences in detectability according to manufactural lots and according to toxin subtypes

In a series of experiments, we have tested the usefulness and limitations of the Guardian Bio-Threat Alert (BTA) system for detection of staphylococcal enterotoxin B (SEB), botulinum toxins (BTXs) A and B, and ricin. In this report, the BTA system has been further evaluated for toxin subtypes and the detection ability of manufactural lots of the BTA strips. The SEB strips failed to detect staphylococcal enterotoxin A, C, and D; the BTX strips generally failed to detect BTXs C, D, E, and F, but one lot showed positive results for BTXs C and D with very low sample values. Differences were observed in sample values at 1 μg/ml for all main toxins according to the different manufactural strip lots: 3.9-fold difference for SEB, 6.3-fold difference for BTX A, 10.9-fold difference for BTX B, and 6.4-fold difference for ricin. The ricin strips showed high cross reactivity toward RCA120. The BioWarfare Agent Detection Devices system showed much lower sensitivity than the BTA system for BTX and ricin (detection limit: about 10 μg/ml).