Comparison of void volume, mobile phase volume and accessible volume determined from retention data for oligomers in reversed-phase liquid chromatographic systems

The experimental technique of mass spectrometric tracer pulse chromatography was used to determine the void volume, i.e., the total volume of eluent in the column, and the volume of eluent moving freely through the column, i.e., mobile phase volume, for a series of eluents with a C(18)-bonded RPLC column. The interstitial volume of the column was determined by size exclusion chromatography. In order to evaluate the utility of the accessible volumes determined from the retention volumes of homologous solutes, the accessible volume of the column was determined as a function of eluent composition and temperature with polystyrene and polyethylene glycol samples using Martin's Rule. Comparison of these four measured volumes indicated that the experimentally measured accessible volumes did not correspond to either the void volumes, mobile phase volumes or interstitial volumes.     

Studies of left ventricular volume estimation from gated blood pool scan with the use of regression equations

The authors carried out experimental and clinical studies of left ventricular volume measurement using equilibrium-gated blood pool scan. Using phantoms, we experimentally obtained a regression equation between radioisotope levels and camera counts. From this equation, we deduced a regression equation between camera counts and volumes, which was then used for calculation of left ventricular volumes using count technique. In an experiment using phantom with various volumes, we obtained a favorable result that the average absolute error between the true and measured volumes was as small as 6.8%. In 11 patients, we calculated the left ventricular volume and ejection fraction employing the regression equation and compared the calculated values with the values obtained by cinemascopy. This comparison disclosed an excellent correlation (r = 0.955 for end-diastolic volume, 0.997 for end-systolic volume and 0.853 for ejection fraction). Mean absolute error was 16.2% for end-diastolic volume and 16.0% for end-systolic volume. These results indicate that this technique is clinically applicable.     

288.15, 298.15和308.15 K温度条件下甘氨酰甘氨酸在蔗糖-水混合溶剂中的体积性质研究

利用Anton Paar DMA55精密数字密度计测定了288.15, 298.15和308.15 K甘氨酰甘氨酸在蔗糖-水混合溶剂中的密度, 计算了甘氨酰甘氨酸的表观摩尔体积VΦ和极限偏摩尔体积 , 得到了其由纯水溶剂转移至混合溶剂中的迁移偏摩尔体积Δtrs 和理论水化数Nh．根据共球交盖模型, 讨论了迁移偏摩尔体积和水化数的变化规律．结果表明, 甘氨酰甘氨酸带电中心与蔗糖之间的结构相互作用对其迁移体积有正贡献, 且占主导地位．甘氨酰甘氨酸的迁移偏摩尔体积为正值, 且随着蔗糖浓度的增大而增大; 理论水化数随温度升高、蔗糖浓度的增大而减小; 温度升高, 极限偏摩尔体积增大, 迁移偏摩尔体积变化很小．     

Volumes of solid state ions and their estimation

Formula unit volume, Vm, has recently been identified as the key link to a number of thermodynamic functions and has given rise to an alternative approach to thermodynamics for modern inorganic materials (volume-based thermodynamics, VBT). In an earlier publication, we reported over 400 ion volumes for commonly encountered cations and anions derived from crystal structure data which can, in turn, be used to generate formula unit volumes for those ionic salts, for which crystal structure data, which is the preferred source of such volume data, is not available. The purpose of the present paper is to report a further 147 supplementary ion volumes. These are compared to ion volumes obtained from the summation of Hofmann's elemental volumes, a convenient and alternative approach for the estimation of Vm. It is shown that many elusive ion volumes can be estimated using these databases in tandem by adopting the newly proposed isomegethic rule and other volume additivity rules. Generation of volume data for new, hypothetical, and counterintuitive ions, as well as for traditional ions, is now a reality, as is demonstrated.     

Activation and Reaction Volumes for [4+2] and [3+2] Additions Involving Maleic Anhydride

The partial molar volumes of reactants and products of the [3+2] addition of C-(p-nitrophenyl)-N-phenylnitrone to maleic anhydride and of the [4+2] addition of 9,10-dimethylanthracene to the same dienophile were determined, and the reaction volumes were calculated. A new method was suggested for determining the reaction volume. The activation volumes of both reactions were calculated from the dependences of the reaction rates on the external pressure. The volume parameters of the reactions involving the reagents of close size are close. The ratios of the activation volumes to the reaction volumes are unity, which suggests a common concerted mechanism of the reactions. Factors that could be responsible for significant changes in the absolute values of the reaction volume parameters are discussed.     

Defect-assisted conductivity in organic ionic plastic crystals

In order to determine the role of defects (vacancies and extended lattice defects) in the conductivity mechanism of a well studied organic ionic plastic crystal electrolyte, conductivity and mean defect volumes were measured. The ionic conductivity of the salt showed a characteristic phase dependence. Defect volumes, as measured by positron annihilation lifetime spectroscopy, showed increasing rates of expansion with increasing rotational disorder. The dependence of ionic conductivity on defect volume was observed to be phase dependent. Increases in mean defect volume size below approximately 100 cm(3) mol(-1) did not always facilitate ionic conductivity. It was shown that the material undergoes a solid-solid phase transition to the most disordered phase (a plastic crystalline phase with the highest conductivity) when the mean defect volume becomes larger than the molar volume of either the rotating anionic or cationic species. Conductivity in this phase had the strongest dependence on defect volume. Critical volumes calculated from the free volume model of Cohen and Turnbull were unrealistically large.     

Partial molar volumes of 18-crown-6 ether in organic solvents at 25°C

The partial molar volumes at infinite dilution of 18-crown-6 ether (CE) in a variety of polar and polarizable solvents with molar volumes ranging from 18 to 170 cm³-mol^–1, were measured at concentrations ranging from 0.02 to 0.1 mol-L^–1 at 25°C. The partial molar volumes of the solute at infinite dilution showed remarkable dependancy on the molar volume of the solvent. The partial molar volumes at infinite dilution for the CE increases as the solvent molar volume increases.     

Molar excess volumes of 1,4-dioxane+ acetonitrile,n-butylamine+acetonitrile andn-butylamine+1,4-dioxane at different temperatures

Molar excess volumes and partial molar volumes are reported for binary mixtures of 1,4-dioxane + acetonitrile, n-butylamine + acetonitrile and n-butylamine + 1,4-dioxane at five different temperatures and over the complete concentration range. The Prigogine-Flory-Patterson model of solution thermodynamics has been used to predict the excess molar volumes. This work shows the importance of the three contributions: interactional, internal pressure and free volume, to the excess volume.     

Volumetric Properties of Glycerol Formal + Propylene Glycol Mixtures at Several Temperatures and Correlation with the Jouyban–Acree Model

Molar volumes, excess molar volumes, and partial molar volumes were investigated for glycerol formal + propylene glycol mixtures from density measurements at temperatures from (278.15 to 313.15) K. Mixture compositions were varied in 0.05 in mass fraction of both components. Excess molar volumes were fitted to the Redlich?CKister equation and compared with literature values for other systems. The system exhibits positive excess volumes probably due to increased non-specific interactions. The effect of temperature on the different volumetric properties studied was also analyzed. In addition, the volumetric thermal expansion coefficients were calculated. The Jouyban?CAcree model was used for density and molar volume correlations of the mixtures at the different experimental temperatures. The mean relative deviations between experimental and calculated data are 0.04±0.03 and 0.04 ±0.05, respectively, for the density and molar volumes, using the minimum number of data points, the Jouyban?CAcree model can predict density and molar volume with acceptable accuracies (0.06±0.04 and 0.08±0.05, respectively).     

Volumetric properties of the glycerol formal + water cosolvent system and correlation with the Jouyban–Acree model

Excess molar volumes and partial molar volumes were investigated from density measurements for glycerol formal?+?water mixtures at temperatures from 278.15 to 313.15?K. Excess molar volumes are fitted using Redlich–Kister equation and compared with literature values for other systems. The system exhibits negative excess volumes, probably due to increased interactions like hydrogen bonding or large differences in molar volumes of components. The effect of temperature on different volumetric properties studied is also analysed. Besides, the volume thermal expansion coefficients are also calculated as 2.51?×?10^?4?K^?1 for water and 7.24?×?10^?4?K^?1 for glycerol formal at 298.15?K. Finally, the Jouyban–Acree model was used for density and molar volume correlations of the studied mixtures at different temperatures. The mean relative deviations between experimental and calculated data were 0.24?±?0.14% and 0.71?±?0.62%, respectively, for density and molar volume data.     

甘氨酸在多元醇-水混合溶剂中的体积性质

利用精密数字密度计测定了甘氨酸分别在不同组成的乙二醇 水和丙三醇 水混合溶剂中的密度,计算了甘氨酸的表观摩尔体积、极限偏摩尔体积和理论水化数.根据结构水合作用模型讨论了迁移偏摩尔体积的变化规律,并与乙醇 水体系作了比较. 结果表明,甘氨酸分子在醇 水混合溶剂中增体积效应的大小与醇分子所含OH基数目的多少有关,但最直接也是最重要的影响因素是其水合壳层的结构形态. 乙醇 水体系中的增体积效应特别显著与该溶剂结构变化上的微观不均匀性和不连续性有关.     

Cell Volume Effect on the Ferroelectric Stability of Perovskite Oxides PbTiO3 and BaTiO3 from First Principle Calculation

Electronic structure of ferroelectric PbTiO3 and BaTiO3 is calculated by the full potential linearized augmented plane wave method. The total energy as a function of the displacement of Ti-cation is obtained for PbTiO3 and BaTiO3 at different cell volumes. At experimental cell volume, Ti-displacement lowers the total energy and the ferroelectricity is stable. When the cell volume is reduced to 90%, total energy is increased with Ti-displacement and ferroelectricity will disappear. The cell volume effect is also confirmed by comparison of the density of states of Ti and O at different cell volumes.     

L-丝氨酸在正丙醇-水混合溶剂中的体积性质

应用精密数字密度计测定了298.15 K时不同组成的L-丝氨酸-正丙醇-水体系的密度, 计算丝氨酸的表观摩尔体积、极限偏摩尔体积、迁移偏摩尔体积和水化数. 根据结构水合作用模型讨论了迁移偏摩尔体积和水化数的变化规律. 结果表明, 丝氨酸两性离子部分和亲水侧链与正丙醇羟基间的相互作用对其迁移体积有正贡献, 且占主导地位. 丝氨酸在正丙醇-水混合溶剂中的迁移偏摩尔体积为正值, 且随醇浓度的增大而增大. 丝氨酸在正丙醇-水混合溶剂中的水化数随溶液中醇浓度的增加而减小.     

Effect of pressure on the rotational mobility of spin probes in polymers

The effects of pressure on the rotational mobility of three nitroxyl radicals (spin probes) in natural rubber, polyethylene, and butadiene-nitrile rubber SRN-26 have been studied. The activation volumes, activation energies, and pre-exponential factors of spin probe rotation at constant pressure and volume have been determined. The activation volumes of probe rotation (20–70 cm³/mol) increase with increasing size of radicals and differ insignificantly from the activation volumes of the β-relaxation process. In the polar polymer SRN-26, the activation volumes of rotation of radicals are appreciably more than in the nonpolar polymers, natural rubber and polyethylene. These features are apparently due to different volumes of the kinetic chain segment controlling probe rotation. The activation volumes of radical rotation around different molecular axes differ significantly. The activation energy of probe rotation at constant volume is appreciably less than at constant pressure. It has also been shown that the energy necessary for the formation of a fluctuation hole is the main factor that determines temperature dependence of the rotational mobility of low-molecular particles in the polymer.     

Study On The Concentration Effect In Gel Permeation Chromatography. I. A New Model Theory For Concentration Dependence Of Hydrodynamic Volumes And Gpc Elution Volumes

Abstract

A new model theory for concentration dependence of hydrodynamic volumes and GPC elution volumes was proposed. In this theoretical model both the reduction of hydrodynamic volumes and the viscosity phenomena in the interstitial volume are taken into account at the same time. The effective hydrodynamic volumes, Vhs, of a solvated macromolecule decrease with increasing reduced viscosity, (7_sp/c), and the GPC elution volumes,Ves, increase with increasing concentration, c, and intrinsic viscosity,(7), respectively according to the following relations.     

Performance of experimental sample injectors for high-performance liquid chromatography microcolumns

An experimental injector for HPLC microcolumns and a 3-nl conductivity detector connected directly to the injector outlet with a 19-nl tube were used to study injector dispersion, guide the design of improved injectors, and suggest appropriate injection techniques. With regard to the small injection volumes required when no on-column concentration technique is used, we show that in some circumstances: (i) there are two volumes to be considered, the sample volume (that which is intended to be injected) and the effective injection volume (that which contains all the sample after it has completely emerged from the injector). Due to dispersion, the latter is often many times the former. An injector performance factor is defined as the ratio of the two volumes. (ii) A smaller sample chamber volume in an injector does not necessarily produce a proportionately smaller effective injection volume, in which case there is a reduction of peak height that degrades sensitivity without a commensurate reduction in peak width that would improve resolution. (iii) Adjusting the geometry of the sample chamber and stator passage can significantly improve injector performance, as illustrated for sample volumes from 2 nl to 1 microl. (iv) In some cases, reducing the diameter of an injector passageway in an attempt to reduce dispersion actually causes performance to worsen.     

Excess volumes of isomeric butanols with di-n-butyl ether

The excess volumes of four isomeric butanols with di-n-butyl ether were determined at 30°C. The isomeric effect was distinctly observed in the excess volume profiles. 1-Butanol and 2-methyl-l-propanol systems exhibited negative excess volumes throughout the concentration range. The 2-butanol system had positive excess volumes up to 0.9 mol fraction of alcohol after which it became negative, while the 2-methyl-2-propanol system exhibited positive excess volumes throughout the concentration range. NCL Communication No. 4678     

293.15K时咪唑醋酸盐-乙醇二元体系的体积性质及分子间相互作用简

用比重瓶法测定了293.15 K时1-甲基咪唑醋酸盐([Mim]Ac)/1,3-二甲基咪唑醋酸盐([Mmim]Ac)/1-乙基-3-甲基咪唑醋酸盐([Emim]Ac)-乙醇(EtOH)二元体系在全组成范围内的密度. 计算出[Mim]Ac/[Mmim]Ac/[Emim]Ac和EtOH的表观摩尔体积和体系的超额摩尔体积. 用三参数多项式关联拟合了表观摩尔体积与摩尔分数的关系,外推出组分的极限偏摩尔体积和摩尔体积. [Mim]Ac/[Mmim]Ac/[Emim]Ac和EtOH的摩尔体积的外推值与实验值分别在±0.07和±0.04 cm3/mol范围内相一致. 计算出了[Mim]Ac/[Mmim]Ac/[Emim]Ac和EtOH分别在无限稀溶液中的溶剂化系数. 用Redlich-Kister 方程关联拟合了超额摩尔体积与摩尔分数的关系. 分别根据极限偏摩尔体积、摩尔体积与极限偏摩尔体积的差值、溶剂化系数和超额摩尔体积对照讨论了分子间相互作用的强弱. 结果显示,在[Mim]Ac/[Mmim]Ac/[Emim]Ac的浓度无限稀溶液中,[Mim]Ac/[Mmim]Ac/[Emim]Ac-EtOH分子对间相互作用的强弱顺序为[Mim]Ac-EtOH>[Mmim]Ac-EtOH >[Emim]Ac-EtOH;在EtOH的浓度无限稀溶液中,以及体系中[Mim]Ac/[Mmim]Ac/[Emim]Ac的摩尔分数在0.15～0.95间时,[Mim]Ac/[Mmim]Ac/[Emim]Ac-EtOH分子对间相互作用的强弱顺序都为[Emim]Ac-EtOH>[Mmim]Ac-EtOH>[Mim]Ac-EtOH.     

The densities and molar volumes of molten lead(II) dodecanoate/dodecanoic acid mixtures over their complete composition range: Evidence for non-ideal behaviour

Data are presented for the densities and molar volumes of the molten system lead(II) dodecanoate/dodecanoic acid over its complete composition range. For equimolar mixtures, plots of molar volume against temperature show curvature at high temperatures, suggesting deviations from ideal behaviour. Support for this comes from a plot of molar volume at constant temperature against acid mole fraction. Densities and molar volumes are reported for lead (II) carboxylate/carboxylic acid (0.5 mole fraction) and for pure carboxylic acid for the even chain acids C₁₀ to C₁₈. The molar volumes at constant temperature in these cases are linear functions of chain length, although the volume occupied per methylene group in equimolar mixtures is suggested to be slightly smaller than with pure soap or pure acid. An explanation for non-ideal behaviour becoming more marked at higher temperature is given in terms of acid monomer-dimer equilibria.     

PACKING OF IONS IN SILICATE GLASSES

Any silicate glass can be regarded as the relaxation of SiO_2 glass and the volumeis composed of two parts. One is the topological volume of O~(2-), which is equal to thevolume per oxygen of SiO_2 glass, the other is the topological volumes of cations. Thetopological volume of a monovalent cation equals the volume shared by each sphere indense haphazard packing of equal spheres of the cation's size. The charges of bivalentcations cause a decrease of volume, the decrement being the packing volume of Ca~(2+). Anequation is reached for the calculation of the volume per oxygen of silicate glasses. Alot of calculations show that the equation is accurate, so accurate that the densities canbe calculated. The study reveals some characters of the glass structure and clearly ex-presses the contributions of various cations to the volumes of glasses.