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ABSTRACT: This study outlines some observations of the pressure effect for gas phase ion-molecule reactions of anthraquinone derivatives with dimethyl ether in an external source ion trap mass spectrometer. At the reagent pressure of 7.998 x 10(-2) Pa, formation of the protonated ions, [M + 13]+, [M + 15]+, and [M + 45]+ ions, of anthraquinones can be observed. However, at the pressure of 1.066 x 10(-2) Pa, formation of molecular ions and many fragment ions of the M+. or [M + H]+ ions have been observed. Since the pressure effect is notable within a small range of pressures for many compounds, it is important to draw attention to the use of the ion trap with an external source where other factors such as ion source residence time may play a role. This can also provide some information for better and more careful controls of the reagent pressure in order to obtain fair CI spectra in an external source ion trap mass spectrometer.
Analytical Sciences 05/2001; 17(4):515-8. · 1.25 Impact Factor
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ABSTRACT: Gas-phase ion-molecule reactions of anthraquinone derivatives with dimethyl ether (DME) were investigated using an external source ion trap mass spectrometer. Semi-empirical calculations were executed to determine possible reactive sites for the product ions. Collision activated dissociation (CAD) was successfully performed for very low abundance of ion-molecule products. Even for product ions with a relative intensity below 1%, CAD experiments can be successfully performed. Significantly more structural information could be elucidated based on this special feature. Importantly, the CAD spectra of very minor ions could be measured by this ion trap instrument, which significantly enhances the future role of the ion trap as a powerful analytical instrument. CAD of all product ions on anthraquinone compounds typically eliminates neutral molecules such as CO or H(2)O. A hydration phenomenon in the CAD processes resulting from the precursor ions incorporating one molecule of H(2)O and then eliminating one molecule of CO was observed in this study.
Rapid Communications in Mass Spectrometry 02/2001; 15(21):1977-87. · 2.79 Impact Factor
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ABSTRACT: Novel results on the selective self-ion/molecule reactions (SSIMR) in both external and internal source ion trap mass spectrometers are demonstrated. Selective self-ion/molecule reaction product ions were produced between the oxygenated and nitrogenated crown ethers. For the oxygenated crown ethers, self-ion/molecule reactions lead to the formation of the protonated ions, adduct ions of fragments ([M + F](+)) and [M + H(3)O](+), while the nitrogenated crown ethers produce [M + H](+), [M + CH](+) and [M + C(2)H(3)](+) ions.
Rapid Communications in Mass Spectrometry 02/2001; 15(15):1309-16. · 2.79 Impact Factor
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ABSTRACT: The preservation of normal nerve function or identification of nerve route is critical in some surgeries of cerebellopontine angle tumors. Over the last 5 years, intraoperative facial nerve electromyogram (EMG) and brainstem auditory evoked potential (BAEP) were applied for evaluation of facial nerve integrity and brainstem function in patients while undergoing resection of cerebellopontine angle (CPA) tumor. This report represents the retrospective analysis of our results.
The inhalational anesthesia with 1-1.5% isoflurane in pure O2 was used. Muscle relaxation was maintained with continuous infusion of atracurium. The degree of muscle relaxation was aimed at a T4/T1 ratio of train-of-four response more than 20% of the adductus pollicis upon ulnar nerve stimulation at the wrist. In 236 patients suffering from CPA tumor without facial palsy, the EMG of the mentalis muscle ipisilateral to the tumor was obtained through stimulation of the facial nerve. The stimulation was applied with a nerve finder, which delivered an electrical stimulation of a single 2 mamp direct current. The EMG finding was compared with the clinical result. In 198 patients, BAEP was used to monitor the brainstem function during tumor resection. In case of intact hearing the BAEP was taken ipsilateral to the operation side and in case with total hearing loss contralateral BAEP to operation side was used. For BAEP stimulation, 90 db click sound stimulation with frequency of 11.26 Hz was applied to both ears. BAEP signals were obtained and recorded at the mastoid region of either side in reference to the vertex. The EMG and BAEP signals were recorded and saved to an evoked potential monitor.
In facial nerve EMG monitoring, there were two false positive and no false negative tests. Except for the two false positive tests, the postoperative clinical results in the other cases were compatible with the intraoperative facial nerve EMG findings. In BAEP monitoring, there were twenty-eight positive tests.
The low incidence of false negative test suggests that facial nerve EMG is valuable in detection of facial nerve function in CPA tumor resection. Intraoperative BAEP abnormality is possibly useful in identifying postoperative brainstem dysfunction.
Acta anaesthesiologica Sinica 10/1997; 35(3):141-7.
