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31.
F. J. Molina A. O. Vila C. Llcer M. J. Martos J. E. Figueruelo 《Journal of separation science》1991,14(9):590-592
Internal calibration in modified hydrodynamic chromatography has been realized by the approach of Prieve and Hoysan, i.e. the use of polystyrene monodisperse latexes to evaluate the equivalent capillary radius, R. The value obtained has been used to estimate the average sizes of a variety of liposome samples from egg yolk lecithin. 相似文献
32.
合成了1-甲基-3-羟乙基咪唑四氟硼酸盐离子液体([C2OHmim]BF4),用红外光谱表征了其结构。以所合成的离子液体作为还原剂、稳定剂与反应介质制备了Ag纳米微粒,用XRD和TEM对微粒的结构和形貌进行了表征。在四球摩擦磨损实验机上研究了[C2OHmim]BF4离子液体及掺入Ag纳米微粒后的离子液体的摩擦学性能。掺入银纳米微粒后,离子液体在高载荷下的润滑性有了大幅的改善。用SEM和XPS分别对磨痕表面的形貌和元素组成、化学状态进行了分析,结果表明:在低、高载荷分别起润滑作用的是有机膜和金属-有机复合膜。 相似文献
33.
Delatour T 《Analytical and bioanalytical chemistry》2004,380(3):515-523
Liquid chromatography–tandem mass spectrometry (LC-MS/MS) is a versatile coupling system which combines both selectivity and sensitivity and certainty. Hence, it is generally considered as the most reliable technique to quantify chemical compounds in complex matrices. In the present paper, we evaluate the performance of LC-MS/MS methods for the quantification of 3-nitrotyrosine in human urine in order to point out its dependence on the design of the quantification method, and emphasize the role of matrix effects in the performance. We compare external and internal calibrations, isotope dilution and isotopomer-based exact matching. The role of both sample preparation and multiple transitions monitoring is particularly addressed. 相似文献
34.
The densities of ethanol and ethanol–water mixtures were measured with a vibrating tube densimeter at 25.0, 50.0 and 75.0 °C in the pressure range from 0.10 to 40.00 MPa. Densities were correlated using an empirical model. Partial molar volumes, excess molar volumes, isothermal compressibilities, cubic expansion coefficients and internal pressures were calculated from obtained densities. This study reports the dependence of densities, partial molar volumes, excess molar volumes, isothermal compressibilities, cubic expansion coefficients and internal pressures on composition, temperature and pressure. 相似文献
35.
ICP-AES中内标法的应用研究 Ⅲ.用内标法校正基体干扰 总被引:1,自引:0,他引:1
通过观测基体对分析元素发射强度的干扰情况,分析干扰机制,从而确定用来校正基体干扰的内标元素与分析元素的匹配条件。实验结果表明,只要选择合适的内标元素,可以校正基体干扰。 相似文献
36.
37.
A homologous series of 2,4-dichlorobenzyl alkyl ethers (DCBEs) have been synthesized and purified for use as retention index calibrants and internal standards. They are stable, sensitive to ECD and FID and ideal for GC-MS, with base peaks at m/z 159/161. The retention index calibration against the n-alkanes for a linear temperature program (LTP) series is given and recommendations made for the most suitable members of the DCBE series for use as internal standards in organochlorine (OC) residue analysis. 相似文献
38.
WANG Yan-xia YE Song 《高等学校化学研究》2006,22(4):520-523
IntroductionPhotochemical reactions, which involve a three-membered ring, have been of great interest to experi-mental photochemists[1—10]. A main reason for thisphenomenon is that the cyclopropane ring exhibits somereaction characteristics of double bon… 相似文献
39.
W. Ren 《Colloid and polymer science》1992,270(10):990-998
Inverse relaxation is studied for hard elastic polypropylene (HEPP), rubber and non-elastic polypropylene. The results show that contractive stress, stress, and internal friction are three essential factors related to the phenomenon. A three-element model in which each element has a definite meaning is proposed to describe this phenomenon. The results also show that, in the first cyclic deformation, relaxation time increases with the increase of recovery for all the materials, which indicates that recovery viscosity increases with the increase of recovery, but the stress rising amplitude (SRA) of inverse relaxation has a maximum in the recovery range. Analysis indicates that SRA equals recovery internal friction (RIF) for ideal material in which stress is solely a function of strain, independent of paths, and approximately equals RIF for non-ideal material at a given strain. From this principle it is found that the order of the work counteracted by RIF for the four materials is the same as that of their second hysteresis loop, and the RIF of HEPP has a sudden increase at the later recovery range. 相似文献
40.
Antonio Fernández-Ramos Benjamin A. Ellingson Rubén Meana-Pañeda Jorge M. C. Marques Donald G. Truhlar 《Theoretical chemistry accounts》2007,118(4):813-826
This article shows how to evaluate rotational symmetry numbers for different molecular configurations and how to apply them
to transition state theory. In general, the symmetry number is given by the ratio of the reactant and transition state rotational
symmetry numbers. However, special care is advised in the evaluation of symmetry numbers in the following situations: (i)
if the reaction is symmetric, (ii) if reactants and/or transition states are chiral, (iii) if the reaction has multiple conformers
for reactants and/or transition states and, (iv) if there is an internal rotation of part of the molecular system. All these
four situations are treated systematically and analyzed in detail in the present article. We also include a large number of
examples to clarify some complicated situations, and in the last section we discuss an example involving an achiral diasteroisomer. 相似文献