We report on the first evidence of electron capture dissociation (ECD) in a radio frequency (rf) ion trap. Peptide ions, [substance P]2+, trapped in a two-dimensional, linear rf ion trap were cleaved by electrons injected along the central axis of the trap. Along the axis, the rf field component was zero and a magnetic field of 50 mT was applied. This electron injection scheme keeps the energy of the electrons below 1 eV, preventing them from heating by the rf field. The present ECD efficiency is approximately 4% by irradiation of electron current of 0.2 microA for 80 ms. ECD in rf traps may open high-throughput and low-cost ECD applications to obtain molecular structure information complementary to collision-induced dissociation.
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.
We propose and demonstrate a new method for multiple-stage mass spectrometry (MSn), collision-activated infrared multiphoton dissociation (CA-IRMPD), which is very effective for the quadrupole ion trap mass spectrometer (QITMS). CA-IRMPD uses a combination of focused laser irradiation (beam radius, approximately 0.4 mm) and collisional activation by a supplemental AC voltage between endcap electrodes. This combination enables IRMPD, which has conventionaLly been ineffective above 10(-4) Torr, to be used under a standard bath gas pressure of 2-8 mTorr. CA-IRMPD can produce richer spectra of product ions than CID or IRMPD while maintaining high sensitivity and mass resolution; thus, it will contribute to an accurate determination of peptide sequences.
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