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EP Sheretov VS Gurov MV Dubkov OV Korneeva 《Rapid communications in mass spectrometry : RCM》1999,13(16):1699-1702
In this article we compare the classical monopole mass filter of von Zahn and the monopole mass filter with a hyperbolic V-shaped electrode. The experimental results and those of computer simulation for both mass spectrometers are presented. We show that the replacement of a conventional 90 degrees V-shaped electrode by an electrode with a hyperbolic profile substantially improves the peak shape of any given mass, and increases the mass resolution by a factor of 3-4 and the abundance sensitivity by a factor of 100. The potential of high analytical performance combined with electroforming techniques for electrode manufacture indicate future practical uses of such instruments. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements
have been reported for the Co1.1−x
Zn
x
Ge0.1Fe1.2O1 spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic
ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained
under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important
role of magnetic anisotropy (due to the presence of Co2+ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed. 相似文献
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MV Muftakhov YV Vasil'ev VA Mazunov 《Rapid communications in mass spectrometry : RCM》1999,13(12):1104-1108
Appearance energies of [M-H](-) ions from carbonyl compounds R-CO-R' (R,R' = H, CH(3), NH(2), OH) have been measured by means of negative ion mass spectrometry in resonant electron capture mode. Values of electron affinity of the corresponding radicals, CH(2)&dbond;C(X)O, NH&dbond;C(X)O and O&dbond;C(X)O, have been determined. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Jofré VP Assof MV Fanzone ML Goicoechea HC Martínez LD Silva MF 《Analytica chimica acta》2010,683(1):126-4586
A new method was developed for analyzing sulfur compounds in the aroma of white wines using ultrasound assisted-emulsification-dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry detection. In the present work, the analytical method for simultaneous determination of seven sulfur compounds (methylmercaptoacetate, methyl(methylthio)acetate, 2-methylthioethanol, 3-methylthiopropanol, 3-methylthiohexanol, 4-methylthio-4-methyl-2-pentanone and hexanethiol) is reported. Parameters that affect the efficiency of the methodology such as extracting and dispersing solvents, sample volume, ion strength, cavitation time and centrifugation time were investigated using a fractionated factorial 26-1 (R = V) screening design. Then, the factors presenting significant positive effects on the analytical response (extracting volume, ion strength, cavitation time and centrifugation time) were considered in a further central composite design to optimize the operational conditions for the ultrasound assisted-emulsification-dispersive liquid-liquid microextraction procedure. Additionally, multiple response simultaneous optimization by using the desirability function was used to find the optimum experimental conditions. The best results were obtained using pH sample 4.25, extractant volume 150 μL, ionic strength 8.75% NaCl, cavitation time 20 s and centrifugation time 50 s. The use of the optimized ultrasound assisted-emulsification-dispersive liquid-liquid microextraction technique allowed to obtain the best extraction results with the minimum interference from other substances from the matrix, and it allowed to quantify the analytes in white wine samples by calibration graphs. Recoveries ranging from 91.99% to 125.87% for all sulfur compounds proved the accuracy of the proposed method in white wine samples. Method detection limits were in the range of 0.36-1.67 ng mL−1 and limits of quantitation were between 0.63 and 3.02 ng mL−1 for sulfur compounds in white wine samples. The proposed methodology was successfully applied for the determination concentrations of sulfur compounds in different commercial Chardonnay wine samples from Mendoza, Argentine. 相似文献
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