Yasuaki Takada

Micellar electrokinetic chromatography—mass spectrometry using a high-molecular-mass surfactant on-line coupling with an electrospray ionization interface

On-line coupling between micellar electrokinetic chromatography (MEKC) and mass spectrometry (MS) was studied with a high-molecular-mass surfactant and an electrospray ionization interface (ESI). A high-molecular-mass surfactant, butyl acrylate-butyl methacrylate-methacrylic acid copolymer sodium salt (BBMA), was employed as a pseudo-stationary phase for an on-line MEKC-MS system. BBMA and a minor component separated by size-exclusion chromatography were determined by ESI-MS. No major ion from the BBMA polymer was detected. The BBMA micelle functioned successfully as the pseudo-stationary phase in a 10 mM ammonium formate buffer containing 10% methanol. Five standard compounds, phenyltrimethylammonium chloride, 1-naphthylamine, quinine sulfate, tetraphenylphosphonium chloride and octaoxyethylenedodecanol, were separated by MEKC and detected by MS. The effects of the concentrations of BBMA on the separation and sensitivity in MEKC-MS were studied. MEKC-MS with BBMA was applied to the separation and detection of a standard mixture of sulfamides.

A sonic spray interface for the mass analysis of highly charged ions from protein solutions at high flow rates.

We have improved the sonic spray interface to enable the analysis of multiply charged ions of protein from a solution at a flow rate of 1 mL/min using a conventional liquid chromatograph/mass spectrometer. In this interface, we added a multihole plate in front of the sampling orifice of a mass spectrometer. This plate does not have a hole coaxial to the sampling orifice but has small holes around the central region of the plate. The plate reduces the density of the solvent molecules in the sprayed gas introduced into the vacuum region through the sampling orifice from the atmosphere and prevents the ions from being solvated and becoming charged droplets due to the cooling that follows adiabatic expansion of the sprayed gas. With this improvement, multiply charged ions whose charge distribution ranged from 11+ to 16+ were analyzed from a 1 μM cytochrome c solution at a high flow rate of 1 mL/min without using a splitter.

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.

High-throughput walkthrough detection portal for counter terrorism: detection of triacetone triperoxide (TATP) vapor by atmospheric-pressure chemical ionization ion trap mass spectrometry.

With the aim of improving security, a high-throughput portal system for detecting triacetone triperoxide (TATP) vapor emitted from passengers and luggage was developed. The portal system consists of a push-pull air sampler, an atmospheric-pressure chemical ionization (APCI) ion source, and an explosives detector based on mass spectrometry. To improve the sensitivity of the explosives detector, a novel linear ion trap mass spectrometer with wire electrodes (wire-LIT) is installed in the portal system. TATP signals were clearly obtained 2 s after the subject under detection passed through the portal system. Preliminary results on sensitivity and throughput show that the portal system is a useful tool for preventing the use of TATP-based improvised explosive devices by screening persons in places where many people are coming and going.

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.

RECENT PROGRESS IN ATMOSPHERIC PRESSURE IONIZATION MASS SPECTROMETRY

Abstract Atmospheric pressure ionization (API) is used as an interface in liquid chromatography-mass spectrometry and capillary electrophoresis-mass spectrometry. In API, quasi-molecular ions of biological molecules in solution are produced at atmospheric pressure. There have recently been several significant advances in spray ionization techniques, which use a solution spraying process. This article gives an overview of three spray ionization techniques: electrospray, ion spray, and sonic spray. It presents their characteristic features and describes the ion formation processes from charged droplets. Furthermore, the charged droplet formation process for each technique is described in terms of the non-uniformity in positive and negative ions in solution as well as in terms of the atomization process.

High-Throughput Walkthrough Detection Portal as a Measure for Counter Terrorism: Design of a Vapor Sampler for Detecting Triacetone Triperoxide Vapor by Atmospheric-Pressure Chemical-Ionization Ion-Trap Mass Spectrometry

Aiming to prevent terrorist attacks in places where many people are coming and going, we have been developing a “high-throughput detection portal system.” The portal system consists of a vapor sampler, an atmospheric-pressure chemical-ionization ion source, and an explosives detector based on ion-trap mass spectrometry. The vapor sampler was designed to be installed in an automated ticket gate of a train station. By optimizing the shape of the nozzle that controls the air flow of the vapor sampler, triacetone triperoxide (TATP) vapor could be detected at a high throughput, i.e., 1200 persons/hour. The false-positive rate of the detection portal system for TATP was evaluated by a field test performed at a train station. A multi-marker logic to determine whether TATP existed or not was adopted, and no false-positive alarms were obtained for over 3000 passengers during the field test. However, acetone, which is an inflammable liquid, was accidentally detected from the passengers during the field test. It is concluded from this detection result that this detection portal system is useful for detecting dangerous chemicals that have high vapor pressure (such as TATP and inflammable liquids) in places where many people are coming and going.

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.

Electrostatic ion guide using double cylindrical electrode for atmospheric pressure ionization mass spectrometry

A novel electrostatic ion focusing lens that consists of two cylindrical electrodes positioned coaxially with each other is described. Square openings are formed in the inner electrode and their angular positions alternate by 90° with respect to the neighboring openings in the axial direction. When a potential difference is applied between the inner and outer electrodes, an electric field penetrates into the interior of the inner electrode through the openings. In the capillary electrophoresis/mass spectrometry analysis of peptides, use of the lens makes it possible to apply a higher voltage to the postacceleration dynode and the signal to background ratio is improved by a factor of 7.

Mass spectroscopic studies of protonation to amino-acid molecules in atmospheric pressure spray

Abstract Positive ions produced by an atmospheric pressure spray from aqueous solutions of alanine, leucine, threonine, serine, aspartic acid, and glutamic acid are detected with a double focusing mass spectrometer to study the origin of the observed ions. The relative intensities of the protonated amino-acid molecules (MH + are found to be grouped into three: (alanine and leucine)> (threonine and serine)>(aspartic and glutamic acids). This trend is ascribed to the difference in the protonation to M in the charged droplets during the spray. A qualitative explanation is proposed on the basis of the Gibbs energy of hydration.