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81.
Dennis F. Thekkudan Sarah C. Rutan Peter W. Carr 《Journal of chromatography. A》2010,1217(26):4313-4327
Simulated chromatographic data were used to determine the precision and accuracy in the estimation of peak volumes (i.e., peak sizes) in comprehensive two-dimensional liquid chromatography in time (LC × LC). Peak volumes were determined both by summing the areas in the second dimension chromatograms and by fitting the second dimension areas to a Gaussian peak. The Gaussian method is better at predicting the peak volume than the moments method provided there are at least three second dimension injections above the limit of detection (LOD). However, when only two of the second dimension signals are substantially above baseline, the accuracy and precision of the Gaussian fit method become quite poor because the results from the fitting algorithm become indeterminate. Based on simulations in which the modulation ratio (MR = 41σ/ts) and sampling phase (?) were varied, we conclude for well-resolved peaks that the optimum precision in peak volumes in 2D separations will be obtained when the MR is between two and five, such that there are typically four to ten second dimension peaks recorded over the eight σ width of the first dimension peak. This sampling rate is similar to that suggested by the Murphy–Schure–Foley criterion. This provides an RSD of approximately 2% for the signal-to-noise ratio used in the present simulations. The precision of the peak volume of experimental data was also assessed, and RSD values were in the range of 4–5%. We conclude that the poorer precision found in the LC × LC experimental data as compared to LC may be due to experimental imprecision in sampling the effluent from the first dimension column. 相似文献
82.
The present study focuses on the evaluation of 1.0 mm i.d. (internal diameter) columns on a commercial Ultra-High Pressure system. These systems have been developed specifically to operate columns with small volumes, typically 2.1 mm i.d., by reducing extra-column volume dispersion. The use of columns with smaller i.d. results in a reduced solvent consumption and required sample volume. The evaluation of the columns was carried out with samples containing neutral and pharmaceutical compounds. In isocratic mode, the extra-column volume produced additional band broadening leading to poor performances compared to equivalent 2.1 mm i.d. columns. By increasing the length of the column, the influence of the extra-column bandspreading could be reduced and 75,000 plates were obtained when four columns were coupled. In gradient mode, the effect of the extra-column contribution on efficiency was limited and about 80% of the performance of the 2.1 mm i.d. columns was obtained. Optimum conditions in gradient mode were further investigated by changing flow rate, gradient time and column length. A different approach of the calculation of peak capacity was also considered for the comparison of the influence of these different parameters. 相似文献
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M.A. Koshelev 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(3):550-552
Broadening and shifting of the 211-202 transition of H216O, H217O, H218O by pressure of water, nitrogen and oxygen were precisely measured at room temperature using spectrometer with radio-acoustic detection of absorption. Shift parameters for all studied lines as well as broadening parameters of H217O, H218O lines were measured for the first time. Comparison of obtained results with previously known experimental and theoretical data is presented. 相似文献
86.
O.M. Lyulin I. Morino R. Kumazawa 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(3):531-539
The absorption spectra of methane at different path lengths and different pressures for three temperatures 180, 240 and 296 K have been recorded in the 5556-6166 cm−1 region using the Bruker IFS 120 HR and 125 HR high-resolution Fourier transform spectrometers. The multispectrum fitting procedure has been applied to these spectra to recover the spectral line parameters. The main goal of this procedure was the determination of self-broadening and self-pressure-induced shift coefficients and the exponents of their temperature dependences. These parameters have been derived for 406 assigned lines with good values of the signal to noise ratio. The rotational dependence of these parameters is discussed. 相似文献
87.
测量了磁性纳米Fe3O4颗粒的X射线衍射谱(XRD)、正电子湮没寿命谱(PALS)和符合多普勒展宽谱(CDBS),研究了不同压力和退火温度对磁性纳米Fe3O4颗粒物相、电子结构、缺陷及电子动量分布等的影响. XRD,PALS,CDBS测量结果表明:纳米Fe3O4颗粒的缺陷浓度随压力的增加而增大,但物相和缺陷类型并未发生变化;磁性纳米Fe3O4<
关键词:
正电子
3O4')" href="#">Fe3O4
寿命谱
多普勒展宽谱 相似文献
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Chung-jong BongKwon-sang Ryu Seung-hoon NahmEun Kyu Kim 《Journal of magnetism and magnetic materials》2011,323(5):379-382
We present a magnetic and nondestructive method to evaluate the remanent life of modified 9Cr-1Mo steel by measuring the reversible magnetic permeability. Specimens with ten different kinds of aging periods were prepared using an isothermal heat treatment at 690 °C. The Larson-Miller parameter (LMP) was calculated and the peak interval of reversible magnetic permeability (PIRMP) was measured using the surface type probe. PIRMP was inversely proportional to LMP. We can evaluate the remanent life of modified 9Cr-1Mo steel using the relationship between PIRMP and LMP. Also, we present the possibility that the tensile strength and yield strength measured by destructive methods could be estimated by PIRMP measured nondestructively. 相似文献