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11.
The speed of sound u in and densities of eight binary mixtures of p-dioxane (p-C4H8O2) with methylcyclohexane (c-C6H11CH3), 1-chlorohexane (C6H13C1), 1-bromohexane (C6H13Br), p-xylene [C6H4(CH3)2], propylbenzene (C6H5C3H7), methyl acetate CH3COOCH3), butyl acetate (CH3COOC4H9), and amyl acetate (CH3COOC5H11) were measured over the whole composition range at 30°C. Isentropic compressibilities (K
S), Rao's molar sound functions (R), excess molar volumes (V
E), excess isentropic compressibilities (K
S
E
) together with relative change in volume V/12 values, have been obtained for all measured mole fractions. The excess partial molar volume (V1-V
1
0
) of p-dioxane in different solvents have also been estimated. The experimental results have been analyzed in terms of the Prigogine–Flory–Patterson theory of solutions. 相似文献
12.
13.
Surface diffusion in reversed-phase liquid chromatography (RPLC) using silica gels bonded with C1 and C18 alkyl ligands of different densities was studied from the viewpoints of two extrathermodynamic relationships, i.e., enthalpy-entropy compensation (EEC) and linear free energy relationship (LFER). First, according to the four methods proposed by Krug et al., the values of surface diffusion coefficient (Ds) were analyzed to confirm that an actual EEC resulting from substantial physico-chemical effects takes place for surface diffusion. Then, it was also demonstrated that a LFER is observed between surface diffusion and the retention equilibrium. The establishment of EEC and LFER suggests a mechanistic similarity of molecular migration by surface diffusion, irrespective of the alkyl chain length and the densities of C1 and C18 ligands. Finally, a thermodynamic model for the LFER based on the real EEC was used to estimate Ds values under various RPLC conditions. The Ds values can be estimated with a mean square deviation of about 25–30%. The agreement between the Ds values estimated and those experimentally measured suggests that the total mass flux by surface diffusion consists of the two contributions due to C1 and C18 ligands and that the contribution of each ligand is proportional to the ligand density. 相似文献
14.
Studies on Phase Behavior of Alkyl Polyglucoside Based on Microemulsions with Modified Fishlike Phase Diagram 总被引:1,自引:0,他引:1
JinLingCHAI GanZuoLI ZhaoYuDIAO GaoYongZHANG 《中国化学快报》2004,15(3):361-364
The three-phase behavior in the quaternary system of an alkyl (C8/10^- or C12/14^-)polyglucoside / 1-butanol / n-octane / water has been studied at 40℃ with the modified fishlike phase diagram, which is presented by us for the first time. The mass fraction of 1-butanol in the hydrophile-lipophile balanced interfacial layer, A^S, the coordinates of the start point B and the end point E of the phase diagram, and the solubilities of alkyl polyglucoside and 1-butanol in n-octane phase were calculated. The solubilization of the microemulsion was also discussed. 相似文献
15.
A novel and simple method for the determination of active endocrine disrupter compounds (octylphenol OP, and nonylphenol NP) in paper using microwave-assisted extraction (MAE) and headspace solid-phase microextraction, coupled with gas chromatography-mass spectrometry has been developed. Parameters affecting the efficiency in the MAE process such as exposure time and extraction solvent were studied in order to determine operating conditions. The optimised method was linear over the range studied (1.25-125 microg kg(-1) for OP and 9.50-950 microg kg(-1) for NP) and showed good level of precision, with a RSD lower than 10% and detection limits at 0.10 and 4.56 microg kg(-1) for OP and NP, respectively. The results obtained from six different types of paper revealed the presence of the target compounds in all samples analysed, at levels ranging between 3 and 211 microg kg(-1). 相似文献
16.
The separation, characterization, and determination of mixtures of alkyl ether sulfates (AES) and fatty acids (C10-C16) in background electrolytes (BGEs) containing acetonitrile (ACN)-water mixtures is addressed. Due to inhibition of the ionization of the carboxylate groups, the migration time and the resolution between the fatty acids decreased when the water content of the BGE was reduced, but efficiency and resolution between the AES oligomers improved. The migration times increased and resolution improved by substituting 5% ACN by an equivalent amount of dioxane. A complete separation of the two surfactant classes, up to the AES oligomers with 8 ethylene oxide units (EOs) with respect to C10, with excellent resolution between the AES oligomers, while preserving a satisfactory resolution between the fatty acids, was achieved with a BGE containing 5 mM trimethoxybenzoic acid, 7 mM dipentylamine, 85% ACN, 5% dioxane, and 10% water. The two surfactant classes were increasingly resolved by further reducing the water content of the BGE. Thus, C2 (acetate) was resolved from the AES oligomers up to 7 EOs using 90% ACN and 5% dioxane, but the resolution between the heavier fatty acids was poor with this BGE. Identification of the AES oligomers was eased by the excellent regularity of the successive migration times; thus, within each AES subclass or series of oligomers with the same number of carbon atoms in the alkyl chain, the migration times decreased following a mild curve as the number of EOs increased. The way how the data obtained by indirect photometry (corrected peak areas that are proportional to the molar concentrations) should be managed to avoid systematic error when the calibration curve is constructed using an AES standard with an oligomer distribution different from that of the samples is discussed and equations are given. Decyl sulfate was successfully used as internal standard. The detection limits (S/N = 3) were of ca. 2 microM for individual AES oligomers. 相似文献
17.
18.
Xiu-Kui Qu Lan-Ying Zhu Ling Li Xi-Lian Wei Feng Liu De-Zhi Sun 《Journal of solution chemistry》2007,36(5):643-650
As a continuation of our previous investigation, interactions between cyclodextrin (β-CD), γ-cyclodextrin (γ-CD) and alkyl trimethylammonium bromides in aqueous solutions have been studied with titration calorimetry and 1H NMR at 298.15 K. The results are discussed in terms of the amphiphilic interaction of CD with surfactants and the iceberg
structure formed by water molecules existing around the hydrophobic tail of surfactant molecules. The stoichiometry of the β-CD–surfactant system is 1:1 whereas that of the γ-CD–surfactant system is 1:2. The corresponding formation enthalpy (negative) of the complexes of the two systems decreases
with an increase in the number of carbon atoms (n) in hydrophobic chain of surfactant molecule, C
n
H2n+1, whereas the entropy increases with the enlargement of n. 相似文献
19.
Presence of nonylphenol, octyphenol and bisphenol a in two aquifers close to agricultural, industrial and urban areas 总被引:1,自引:0,他引:1
Active endocrine disruptors (nonylphenol, octylphenol and bisphenol A) were analysed in 2 aquifers and the corresponding surface
waters. They are compounds widely used in industrial processes. The objective of this study was to determine the leaching
potential of these compounds in groundwaters and to eventually correlate these levels with surface water samples. The areas
sampled were agricultural, close to large cities and with an important industrial activity in the surrounding area.
Samples (200 mL) were extracted using off-line SPE with polymeric OASIS 60 mg cartridges. Analyses were performed by gas chromatography-mass
spectrometry (GC-MS) using selected ion monitoring (SIM) and full scan for quantification and unequivocal identification,
respectively. This paper reports the detection limit for the compounds studied (from 0.001 to 0.030 μg L−1), and method performance as regards to linearity (0.01–1.3 μg L−1), reproducibility (less than 9%) and recovery (84 to 95%).
The results from a monitoring program revealed the presence of the target compounds in all samples analysed, at levels of
0.07 and 1.9 μg L−1. The presence of these compounds in groundwater was attributed basically to degradation of inert ingredients present in the
formulation of many pesticides or to the increasing application of sludge in agricultural practice, although the infiltration
of industrial run-off and wastewater disposal cannot be disregarded. 相似文献
20.
The reactions of 1,4-bis[2-(tributylstannyl)tetrazol-5-yl]benzene with α,ω-dibromoalkanes were carried out in order to synthesise pendant alkyl halide derivatives of the parent bis-tetrazole. This led to the formation of several alkyl halide derivatives, substituted variously at N1 or N2 on the tetrazole ring. The crystal structures of 1,4-bis[(2-(4-bromobutyl)tetrazol-5-yl)]benzene (2-N,2-N′), 1,4-bis[(2-(4-bromobutyl)tetrazol-5-yl)]benzene (1-N,2-N′) and 1,4-bis[(2-(8-bromooctyl)tetrazol-5-yl)]benzene (2-N,2-N′) are reported. Further discussion involves the structure of 1,4-bis[2-(6-bromohexyl)-2H-tetrazol-5-yl]benzene (2-N,2-N′) previously reported. 相似文献