Nonlinear dependence of the solubility of water in hydrocarbons on the molar volume of the hydrocarbon

The solubility of water in fifty hydrocarbon solvents at 20°C is estimated by means of the solubility equation derived from the thermodynamics of mobile order in H-bonded liquids. Neglecting the change in nonspecific cohesion forces, and assuming that water is primarily monomeric in solution, the prediction accounts for two main effects: the breaking of the H-bond network linking the water solute molecules together, and the entropy of exchange between water and solvent molecules in solution. The formation of a weak O–H ... hydrogen bond interaction is moreover taken into account according to whether the hydrocarbon is saturated or not. The overall predictive equation foresees a non-linear dependence of the water solubility on the molar volume of the hydrocarbon. Several rules are presented regarding the water solubility-hydrocarbon structure relationship.     

Chromatographic determination of the solubility of low soluble substances—A practical possibility

Using selected examples we demonstrate the determination of solubility of low soluble substances with the help of planar chromatography, which is a new, simple and rapid approach to the problem, to a certain extent challenging the established methods. Our approach is a practical consequence of the thermodynamic view of the chromatographic processes, involving either the adsorption or partition mechanism of separation.

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Chromatographische Bestimmung der Löslichkeit von schwerlöslichen Substanzen — eine praktische Möglichkeit

Zusammenfassung An den gewählten Beispielen wird die Bestimmung der Löslichkeit schwerlöslicher Substanzen mit Hilfe der planaren Dünnschichtchromatographie demonstriert. Dieses Verfahren stellt eine neue, einfache und schnelle Methode dar, die in einem gewissen Maß in Konkurrenz zu den älteren und anerkannten Methoden tritt. Die Methode ist die praktische Konsequenz der thermodynamischen Betrachtung des chromatographischen Prozesses in der Adsorptions- und Verteilungsdünnschichtchromatographie.

     

顶空气相色谱-质谱法测定大型玩具中芳香烃化合物

提出了顶空气相色谱-质谱法测定大型玩具中苯、甲苯、乙苯、间(对)二甲苯、邻二甲苯、萘、蒽等7种挥发性芳香烃残留量的方法。选择顶空平衡温度和时间分别为90℃和40min,用RTX-5色谱柱分离,电子轰击离子源检测。7种芳香烃化合物在一定的质量浓度范围内与其峰面积呈线性关系,方法的检出限(3S/N)在0.02～0.04mg.kg-1之间。在3个添加水平上做回收试验,加标回收率在90.0%～106.8%之间,相对标准偏差(n=7)在0.3%～5.3%之间。     

Molecular ordering in some liquid aromatic hydrocarbons

This study presents a comparison of the structures and molecular correlations for the linear aromatic hydrocarbons: benzene, naphthalene, and anthracene in the liquid phase, performed for the first time by the method of X-ray diffraction. Also for the first time the X-ray diffraction results obtained for anthracene at 513?K have been reported. Monochromatic radiation CuK_α was used to determine the scattered radiation intensity between S _min?=?4π?sin?Θ_min/λ?=?0.417?Å^?1 and S _max?=?4π?sin?Θ_max/λ?=?7.06?Å^?1. The mean angular distributions of X-ray scattered intensity were measured and the differential radial distribution functions of electron density (DRDFs) were calculated. The mean distances between the neighbouring molecules and the mean coordination numbers were found. The most probable models of local ordering of these molecules were suggested. Correlations have been found between the number of benzene rings in the molecules studied and their physical properties.     

Simultaneous determination of volatile aromatic and halogenated hydrocarbons in water and soil by dual-channel ECD/PID equilibrium headspace analysis

Volatile aromatic and halogenated hydrocarbons are determined in water and soil samples by equilibrium headspace gas chromatography. Simultaneous analysis is carried out in a dual column/dual detector arrangement with ECD and PID. Their determination in contaminated soil is performed with the same instrumental configuration. However, in contrast to water analysis, an increased sample temperature was found necessary for highly adsorptive soil specimens. At sample temperatures of 95 °C, recoveries near 100% have been found. Both adsorption and desorption processes were found to be strongly time-dependent.     

Retention of diphenyls,terphenyls, phenylalkanes and fluorene on graphitized thermal carbon black

Summary This paper defines values of retention volumes for zero surface coverage (Henry's constant) at different temperatures, retention indices and variations of the internal energy (differential heats of adsorption) of diphenyl and its alkyl derivatives, terphenyls, diphenylmethane, triphenylmethane, diphenylethanes and fluorene on graphitized thermal carbon black (GTCB). Adsorption on GTCB takes place in accordance with the geometry of these molecules, the strongest adsorption being observed for para-terphenyl with least inhibited internal rotation of the molecule, while the weakest adsorption occurs for 2,6,2,6-tetramethyldiphenyl with the most inhibited internal rotation of the molecules. The flat molecules of fluorene are adsorbed on GTCB more readily than the nonflat molecules of diphenylmethane.     

气相色谱法同时测定甲醇中共存杂质和微量芳烃

提出了甲醇中共存杂质(丙酮、乙酸甲酯、乙醇)和微量芳烃(乙苯、对二甲苯、间二甲苯和邻二甲苯)含量的气相色谱测定方法。用INNOWAX色谱柱,采取程序控制柱温升温,用氢火焰离子检测器,各种化合物完全分离。丙酮、乙酸甲酯和乙醇的线性范围为4.0～20mg.L-1,各芳烃化合物的线性范围为0.4～2.0mg.L-1。方法用于甲醇样品的分析,加标回收率在88%～114%之间,相对标准偏差(n=7)为2.56%～4.68%。     

The effect of some modifiers on the retention of aromatic hydrocarbons on untreated silica gel

Summary The retention parameters of benzene, naphthalene; anthracene and phenanthrene on untreated silica gel were determined in the presence of four modifiers: 1-methyl-2-pyrrolidone (MP), 4-formyl morpholine (FM), -butyrolactone (BL) and sulfolane (SF). Better column performance was found in the case of FM and MP only.     

Asymmetric aryl polyhedral oligomeric silsesquioxanes (ArPOSS) with enhanced solubility

Four new asymmetric Polyhedral Oligomeric SilSesquioxanes (POSS) with the formula (Aryl)Phenyl₇Si₈O₁₂, where Aryl = 1-naphthyl, 2-naphthyl, 9-phenanthrenyl, and 1-pyrenyl, have been synthesized in reasonable yield and high purity. These compounds were characterized with ¹H, ¹³C, ²⁹Si NMR and elemental combustion analysis. These compounds possess polycyclic aromatic functionality, which disrupts symmetry to improve solubility in organic solvents and aromatic polymers, without significant impact on thermal stability.     

Hydrocarbon detection using laser ion mobility spectrometry

A Laser Ion Mobility Spectrometer has been set up and trace detection experiments have been performed. We find that laser ionization almost selectively ionizes aromatic hydrocarbons. Aliphatic hydrocarbons are only laser-ionized in case these contain conjugated double bonds. As, in contrast to radioactive ion mobility spectrometry, background air constituents and air contaminants cannot be ionized, drift spectra are inherently simple and easily interpretable. We show that a laser ion mobility spectrometer can be operated in two basically different modes, either using tunable or fixed-frequency laser sources. In the tunable laser mode, aromatic hydrocarbons can be detected in the positive mode and distinguished from each other on account of their different excitation wavelengths and ion drift times. In the fixed-frequency mode, specially chosen and intentionally admitted aromatic hydrocarbons are laser ionized and the primary ionization is transferred to non-aromatic species by means of atmospheric pressure chemical ionization. In this latter mode of operation nitroglycerin and triacetone triperoxide, two non-aromatic high explosives, could be detected.     

Demetalization of oils resulting from recycled tires by liquid-liquid extraction using modified superheated water An environmentally friendly approach

An approach based on continuous pressurized liquid-liquid extraction with 20% HNO₃/1 M KCl/10⁻³ M EDTA as extractant has been developed for the extraction of metals from the oil resulting from recycled tires. A multivariate optimization of the main variables affecting the extraction process has been performed. The method has been applied to three oil samples with different contents in V, Ni, Zn, Fe and Cu. The target metals have been determined in both untreated and treated oil by flame atomic absorption spectrometry (FAAS) in order to obtain the extraction efficiency. Under the optimum conditions, recoveries higher than 90% have been obtained with a repeatability and within-laboratory reproducibility, expressed as relative standard deviations, ranging from 2.75 to 6.91 and 2.97 to 8.16%, respectively. For applications where the demetalization does not require being complete, a study of the demetalization degree achieved depending on the extraction temperature and extractant composition has also been performed. This study provides useful data about the cheapest working conditions to be used in order to obtain a given demetalization level.     

固定能量同步发光光谱测定法

本文介绍一种分子发光分析新技术——固定能量同步发光光谱测定法(CESLS)。该法系在激发波长和发射波长的同时扫描过程中保,持两者间有一个固定的能量差。它具有比经典发光分析法和固定波长同步发光光谱测定法更为优越的特点,是一种有潜力的多组分分析方法。尤其在PAHs分析中,可望获得广泛应用。本文还讨论了CESLS参数选择的理论优化问题。     

Isobaric vapour–liquid equilibria for the binary systems of fuel oxygenates with aromatic hydrocarbons

Isobaric vapour–liquid equilibrium data at 720?mm?Hg for the binary systems of diisopropyl ether with o-xylene and m-xylene and dimethoxymethane with benzene and toluene are determined. A Swietoslawski type ebulliometer is used for the measurements. The experimental T?x data are used to estimate Wilson parameters and the parameters in turn are used to calculate the vapour compositions and activity coefficients. The activity coefficients are used to calculate molar excess Gibbs free energy (G ^E). All the systems studied here do not exhibit azeotropes. Excess Gibbs free energy values are positive over the entire range of composition for all the systems.     

Superheated water extraction of linear alquilbenzene sulfonates from sediments with on-line preconcentration/derivatization/detection

A fully automated screening method based on superheated water extraction of linear alquilbenzene sulfonates from sediments prior to preconcentration/derivatization/detection is presented. A multivariate optimization of both the extraction step and derivatization step was performed. Superheated water extraction was compared with conventional Soxhlet extraction obtaining better recoveries (>95% versus 80-86%) and a drastic reduction of the extraction time (50 min versus 24 h) by the proposed method. The on-line coupling of the extractor with a preconcentration/derivatization/detection manifold through a flow-injection interface has permitted to obtain a fully automated screening approach. Moreover, this research constitutes an environmentally friendly method due to the use of water as extractant instead of an organic solvent.     

利用气相色谱相对比保留体积估算芳烃的正辛醇/水分配系数

采用气相色谱法在９种常见的固定液上分别测定了１３种芳烃的相对比保留体积,同时对经典的摇瓶法测定了相同化合物的正辛醇／水分配系数,并以此建立了（Ｖｇ〈Ｒ〉－Ｋｖｗ回归方程。利用所建立的回归方程和１３种芳烃化合物的Ｖｇ〈Ｒ〉值对其Ｋｖｗ进行估算的结果表明,选用９种固定液中的任何一种,其Ｋｖｗ估算值的相对误差均在允许的范围内,其中以选用固定液ＤＣ－２００,ＳＥ－３０和ＰＥＧ－２０Ｍ误差较小。