共查询到20条相似文献,搜索用时 187 毫秒
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高速逆流色谱法分离和测定甾体激素 总被引:2,自引:0,他引:2
用自制的高速逆流色谱仪分离两酸睾丸素和氢化可的松注射剂,以氯仿-甲醇-水为溶剂体系及优化的色谱条件,对样品组分作了有效的分离,以苯甲酸为内标,获得令人满意的定量结果,标准偏差小于0.8%。 相似文献
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在0.1mol·L^-1NaHCO3介质中,用伏安法研究了超氧阴离子O2^.-与糖皮质类甾体氢化可的松的化学反应。实验表明,氢化可的松清除O2^.-的化学作用机制为氢化可的松催化O2^.-的歧化反应,氢化可的松是O2^.-的清除剂。氢化可的松催化O2^.-歧化反应的速率对O2^.-为零级表观反应,对氢化可的松则为二级表观反应,求得20℃时氢化可的松催化O2^.-歧化反应表观速率常数k为8.76×10^5L·mol^-1·s^-1。本结果为医学组织研究结果提供了新的实验证据。在抗炎作用方面,氢化可的松除抑制磷脂酶A2的活性从而间接阻止O2^.-的产生外,还能直接化学清除产生的O2^.-,认为氢化可的松的抗炎作用应是这种生物和化学的综合作用结果。 相似文献
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HPLC法测定氯霉素氢化可的松滴耳液中两组分的含量 总被引:1,自引:0,他引:1
采用反相高效液相色谱法,以醋酸泼尼松为内标,UV检测波长为244nm,以YWG-C18为固定相,以甲醇-水(60∶40)为流动相,同时测定了氯霉素氢化可的松滴耳液中氯霉素和氢化可的松的含量,并进行了线性范围和回收率测定,平均回收率(n=6)和相对标准偏差分别为:99.91%和0.86%(氯霉素),99.58%和1.34%(氢化可的松)。 相似文献
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以量子化学方法在密度泛函B3LYP/6-31G(d)水平上计算得到含有电负性原子的溶剂水、醇类、酮类、酯类、氯代烷烃共17种溶剂的结构参数:最高占用轨道能(EHOMO)、分子最低空轨道能(ELUMO)、分子偶极矩(μ)、分子总能量(Etotal) 、最正原子净电荷(q+)、最负原子净电荷(q-)。采用误差反向传播(BP)算法的三层人工神经网络,确定隐含层节点数为7,建立了EHOMO、ELUMO、μ、Etotal、q+、q-、摩尔体积(VM)、介电常数(ε)、温度(T)共9个参数与氢化可的松在不同温度下不同溶剂中的溶解度之间关系的模型。运用此神经网络模型可预测不同分离条件下氢化可的松的溶解度,平均预测相对误差为7.0%。 相似文献
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Haroun M Dufresne C Jourdan E Ravel A Grosset C Villet A Peyrin E 《Journal of chromatography. A》2002,977(2):185-192
The retention of hydrocortisone (used as an amphiphilic model solute) on an immobilized artificial membrane (IAM) column was investigated in relation to the mobile phase concentration of three sodium salts (representing different rankings in the Hofmeister series, i.e. perchlorate, chloride and sulfate) in order to provide insight into the nature of the solute interactions with phospholipid monolayers. The influence of the salt series on solute retention was found to follow the Hofmeister series, emphasizing the role of hydrophobic effect in the solute retention mechanism on phospholipid monolayers. Retention models based on the extended Wyman relations (preferential interaction theory) were developed to analyze more quantitatively the salt effects on the hydrocortisone retention factor. This analysis as well as additional thermodynamic study suggested that the hydrocortisone binding to IAM involved both an insertion into the hydrophobic inside governed by hydrophobic effects and contacts with the interfacial region implying interactions such as van der Waals interactions/hydrogen bonds between the solute hydroxyl groups and the polar headgroups of phospholipidmonolayers. 相似文献
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We have carried out a series of molecular dynamics simulations to investigate the dynamics of X(-)-water (X = F, Cl, Br, and I) and water-water hydrogen bonds in aqueous alkali halide solutions at room temperature and also of Cl(-)-water and water-water hydrogen bonds at seven different temperatures ranging from 238 to 318 K. The hydrogen bonds are defined by using a set of configurational criteria with respect to the anion(oxygen)-oxygen and anion(oxygen)-hydrogen distances and the anion(oxygen)-oxygen-hydrogen angle for an anion(water)-water pair. The results of the hydrogen bond dynamics are obtained for two different cutoff values for the angular criterion. In both cases, similar dynamical behavior of the hydrogen bonds is found with respect to their dependence on ion size and temperature. The fluoride ion-water hydrogen bonds are found to break at a much slower rate than water-water hydrogen bonds, while the lifetimes of chloride and bromide ion-water hydrogen bonds are found to be shorter than those of fluoride ion-water ones but still longer than water-water hydrogen bonds. The short-time dynamics of iodide ion-water hydrogen bonds is found to be slightly faster, while its long-time dynamics is found to be slightly slower than the corresponding water-water hydrogen bond dynamics. Correlations of the observed dynamics of anion(water)-water hydrogen bonds with those of rotational and translational diffusion and residence times of water molecules in ion(water) hydration shells are also discussed. With variation of temperature, the lifetimes of both Cl(-)-water and water-water hydrogen bonds are found to show Arrhenius behavior with a slightly higher activation energy for the Cl(-)-water hydrogen bonds. 相似文献
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Bogumil Brzezinski 《Journal of Molecular Structure》1984,118(3-4):311-318
Heteroconjugated NO+H … N NO … H+N and homoconjugated NO+H … ON NO … H+ON intramolecular hydrogen bonds formed in semisalts of mono- and di-N-oxides of N,N′-tetraalkyl-o-xylyldiamines were studied by IR and NMR spectroscopy. All these hydrogen bonds show large proton polarizability. In the case of the heteroconjugated hydrogen bonds the proton transfer equilibrium shifts from compounds 1 to 3 to the left hand side since the interaction of the hydrogen bond with the solvent environment decreases in this series of compounds. With compound 1 the hydrogen bonds are slightly weaker and longer, hence the wavenumber dependence of the intensity of the continuum caused by these hydrogen bonds is slightly changed with compound 1 compared with compound 2. In the case of compound 3 the intensity of the continuum decreases because of increasing screening of the hydrogen bonds. In the series of homoconjugated hydrogen bonds, from compound 4 to 6 the intense continuum vanishes, and only the band of the 0–1 proton transition at 950 cm−1 remains. The vanishing of the continuum is caused by increasing screening of the hydrogen bonds against their solvent environments by bulky groups, and thus, this change demonstrates again that the interaction of the hydrogen bond with large proton polarizabilities is a necessary prerequisite for IR continua to appear. 相似文献
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We have carried out a series of molecular dynamics simulations to investigate the hydrogen bond and residence dynamics of X(-)-water (X=F, Cl, and I) and pairs in aqueous solutions at a temperature of 673 K. The calculations are done at six different water densities ranging from 1.0 to 0.15 g cm(-3). The hydrogen bonds are defined by using a set of configurational criteria with respect to the anion(oxygen)-oxygen and anion(oxygen)-hydrogen distances and the anion(oxygen)-oxygen-hydrogen angle for an anion(water)-water pair. The F(-)-water hydrogen bonds are found to have a longer lifetime than all other hydrogen bonds considered in the present study. The lifetime of Cl(-)-water hydrogen bonds is shorter than that of F(-)-water hydrogen bonds but longer than the lifetime of water-water hydrogen bonds. The lifetimes of I(-)-water and water-water hydrogen bonds are found to be very similar. Generally, the lifetimes of both anion-water and water-water hydrogen bonds are found to be significantly shorter than those found under ambient conditions. In addition to hydrogen bond lifetimes, we have also calculated the residence times and the orientational relaxation times of water molecules in ion(water) hydration shells and have discussed the correlations of these dynamical quantities with the observed dynamics of anion(water)-water hydrogen bonds as functions of the ion size and density of the supercritical solutions. 相似文献
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The equation of the state of the hydrogen bonding fluid system of AaDd type is studied by the principle of statistical mechanics. The influences of hydrogen bonds on the equation of state of the system are obtained based on the change in volume due to hydrogen bonds. Moreover, the number density fluctuations of both molecules and hydrogen bonds as well as their spatial correlation property are investigated. Furthermore, an equation describing relation between the number density correlation function of "molecules-hydrogen bonds" and that of molecules and hydrogen bonds is derived. As application,taking the van der Waals hydrogen bonding fluid as an example, we considered the effect of hydrogen bonds on its relevant statistical properties. 相似文献
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Substances with intramolecular, easily polarizable hydrogen bonds of different length are compared. Long hydrogen bonds cause IR continua which show band-like structures in the region 2800–1800 cm?1, extending with weaker intensity toward smaller wave-numbers over the whole region studied. Medium length bonds cause continua beginning at 3200 cm?1 and extending over the whole region studied. Very short, easily polarizable hydrogen bonds, such as the bond in the HAuCl4 salt of NN'-tetramethyl-o-xylildiamine di-N-oxide, cause continua with very great intensity in the region 1500–850 cm?1. Comparison of the experimental with calculated continua shows very good agreement with regard to wavenumber regions in which easily polarizable hydrogen bonds of different length cause IR continua.By comparing all these intramolecular, easily polarizable hydrogen bonds causing IR continua it is shown that the charge of the hydrogen bonds is not the decisive property for the occurrence of the continua but rather the shape of the proton potentials. Continua may occur only with hydrogen bonds with double minima or broad flat proton potential. 相似文献
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Dr. Peter Schuster 《Theoretical chemistry accounts》1970,19(2):212-224
CNDO and INDO calculations were performed on numerous structures with hydrogen bonds of different strength. An almost linear relationship is found between the strength of weak hydrogen bonds and the amount of charge transfered.π-electrons and lone pairs are nearly equivalent in hydrogen bonding. The stereochemistry of hydrogen bonds is determined largely by additional interactions betweenσ-bonds of the two molecules. Since proton affinities are calculated too large by the CNDO method, an error is introduced in the potential curves for proton transfer in weak hydrogen bonds. In systems with strong hydrogen bonds both structures with the proton on the right and left have almost the same energy and hence the potential curves for proton transfer are free of the errors mentioned above. 相似文献
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Zakharov BA Kolesov BA Boldyreva EV 《Physical chemistry chemical physics : PCCP》2011,13(28):13106-13116
Predicting behaviour of hydrogen bonds with varying temperature, in particular-correlating donor-acceptor distances in the O-H···O hydrogen bonds with the frequencies of O-H stretching vibrations is important for understanding dynamics of biomolecules and phase transitions in crystals. A commonly used correlation suggested earlier in the literature is based on statistical analysis of different compounds [A. Novak, Structure and Bonding, 1974, 18, 177; K. Nakamoto, M. Margoshes, R. E. Rundle, J. Am. Chem. Soc., 1955, 77, 6480]. The present study is a rare example when correlations between geometry and energy parameters have been found for selected individual hydrogen bonds in the same crystalline compound at multiple temperatures. The properties of several types of O-H···O hydrogen bonds in bis(DL-serinium) oxalate dihydrate and DL-alaninium semi-oxalate monohydrate have been studied by a combination of variable-temperature single-crystal X-ray diffraction and polarized Raman spectroscopy. The changes in the hydrogen bonds geometry could be compared with the changes of the corresponding spectral modes. The correlation suggested by Novak is roughly followed, better for medium and weak, than for short hydrogen bonds. Fine details of spectral changes differ for individual bonds. The way how H-bonds are affected by cooling depends on their environment in the crystal structure. Short O-H···O hydrogen bonds in bis(DL-serinium) oxalate dihydrate expand or remain almost unchanged on cooling, whereas in DL-alaninium semi-oxalate monohydrate all strong H-bonds are compressed under these conditions. The distortion of individual hydrogen bonds on temperature variations is correlated with the anisotropy of lattice strain. 相似文献
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Mejía SM Espinal JF Restrepo A Mondragón F 《The journal of physical chemistry. A》2007,111(33):8250-8256
The potential energy surface of the (ethanol)2-water heterotrimers for the trans and gauche conformers of ethanol was studied using density functional theory. The same approximation was used for characterizing representative clusters of (ethanol)3, (methanol)3, and (methanol)2-water. Trimerization energies and enthalpies as well as the analysis of geometric parameters suggest that the structures with a cyclic pattern in the three hydrogen bonds of the type O-H---O (primary hydrogen bonds), where all molecules are proton donor-acceptor at the same time, are more stable than those with just two primary hydrogen bonds. Additionally, we propose the formation of "secondary hydrogen bonds" between hydrogen atoms of the methyl group of ethanol and the oxygen atom of water or other ethanol molecule (C-H---O), which were found to be weaker than the primary hydrogen bonds. 相似文献