C4馏分中微量乙腈的大口径毛细管色谱测定

采用水相萃取富集技术，利用大口径厚液膜HLZ－60石英毛细管色变柱对C4烃抽余液中的微量乙腈进行分析；结果表明LZP－60石英毛细管色谱柱对乙腈化合物具有良好的惰性和色谱选择性；残余烃杂质峰和大量水分不干扰乙腈峰的流出；定量分析结果表明，样品测量的相对标准偏差为15％，其相对误差为7％，色谱分离检测法完全满足实际工作中微量乙腈分析的需要。     

Excess enthalpies of binary and ternary mixtures of acetonitrile with methanol,ethanol and benzene

Excess molar enthalpies are measured for the binary mixtures methanol—acetonitrile and ethanol—acetonitrile at 25 and 35°C and for the ternary mixtures methanol—acetonitrile—benzene and ethanol—acetonitrile—benzene at 25°C using an isothermal dilution calorimeter. The binary results are well reproduced with an association model which contains four equilibrium constants for the association of alcohol, two equilibrium constants for that of acetonitrile, and two solvation equilibrium constants between alcohol and acetonitrile molecules. The ternary results are compared with those calculated from the model with binary parameters.     

A simple and low-energy strategy for the separation of water and acetonitrile

As acetonitrile is a widely used solvent for the chemical industry, the recovery of acetonitrile from acetonitrile wastewater is significant for both industrial cost reduction and environmental protection. In this article, a simple, low-energy, and low-cost strategy is proposed for the effective separation of acetonitrile from high-concentration acetonitrile wastewater. The approach is based on a sequential combination of two steps: salt-induced phase separation and hydrophobic filtration. The acetonitrile wastewater was first induced to split into two phases by salt, that is, the acetonitrile-rich phase and the water-rich phase, then the above two phases were poured into the hydrophobic filter paper funnel for the separation. It was shown that NaCl is a suitable salting-out reagent, and that hydrophobic filter papers—obtained from modification by butyltrichlorosilane and octyltrichlorosilane were the optimal choice for hydrophobic filtration. The salt-induced phase separation process is able to increase the volume fraction of acetonitrile in the acetonitrile-rich phase up to 92%. The acetonitrile-rich phase can pass through the hydrophobic filter paper, whereas the water-rich phase was intercepted. The hydrophobic filter paper retained strong hydrophobicity and high acetonitrile-separating capacity after 3 months storage, or upon immersion in acetonitrile-water mixtures for 12 h, or applied for 25 consecutive separations.     

Vibrational frequencies and infrared intensities of acetonitrile coordinated with metal cations: an ab initio study

Vibrational frequencies and infrared intensities have been calculated at the 6-31G and 6-31G^** levels for acetonitrile and for the complexes of acetonitrile with Li⁺ and Na⁺ cations. The changes in the infrared characteristics from an isolated acetonitrile to acetonitrile coordinated with metal cations (Li⁺ and Na⁺) have been evaluated. The ab initio calculations predict an essential increase of the intensities of the stretching CN, C-C and deformation CH₃, CCN vibrations in the complexes of acetonitrile with Li⁺ and Na⁺ cations.     

On the exchange of cyanide with acetonitrile. A test of theoretical calculations

- The theoretically predicted formation of an adduct between cyanide and anhydrous acetonitrile was tested experimentally; no evidence for such a complex was found. The previously reported radioactivity loss in the reactions of cyanide - ¹⁴C in acetonitrile solutions was possibly due to protonation and loss of hydrogen cyanide, since no exchange between cyanide and acetonitrile was evidenced within the sensitivity limits of ¹³C labelling. Potassium cyanide and carbonate in the presence of 18-crown-6 ether catalyze the H/D exchange between acetonitrile and trideuteroacetonitrile.     

Real‐Time Observation of Liposome Bursting Induced by Acetonitrile

We show the bursting process of dioleoylphosphatidylcholine (DOPC) liposomes in response to the addition of acetonitrile, a small toxic molecule widely used in the fields of chemistry and industry. The percentage of destroyed liposomes is reduced upon decreasing the acetonitrile fraction in the aqueous solution and vesicle bursting is not observed at volume ratios of 4:6 and below. This indicates that a high fraction of acetonitrile causes the bursting of liposomes, and it is proposed that this occurs through insertion of the molecules into outer leaflet of the lipid bilayer. The elapsed time between initial addition of acetonitrile and liposome bursting at each vesicle is also measured and demonstrated to be dependent on the volume fraction of acetonitrile and the vesicle size.     

反相色谱多二元溶剂的选择性调整

从统计热力学方法推导的溶质保留规律及其相关参数与分子结构之间的关系式出发,探讨了１６种多环芳烃在甲醇／水、乙腈／水、异丙醇／乙腈３种二元溶剂体系下选择性的差异,为确立复杂化合物分离的溶剂选择原则奠定了基础。     

Excess enthalpies and complex formation of acetonitrile with acetone,chloroform, and benzene

Excess enthalpies of binary systems of acetonitrile—acetone, chloroform—acetone and chloroform—benzene, and ternary systems of acetonitrile—chloroform—acetone and acetonitrile—chloroform—benzene are reported at 25°C. The results are analyzed with thermodynamic association theory for complex ternary liquid mixtures. The theory involves two types of self-association of acetonitrile, formation and binary complexes for component pairs of a ternary system, and a nonspecific interaction term expressed by the NRTL equation between various chemical species.     

二阶梯度升温热解吸法测定空气中的微量丙烯腈和乙腈

采用气体采样泵将空气样品的丙烯腈和乙腈吸附到吸附管中,用二阶梯度升温将吸附管中的被测物质解吸到冷阱中,再快速对冷阱升温,将冷阱中的被测物质解吸进入色谱柱进行分离,用气相色谱氢火焰检测器检测空气中的微量丙烯腈和乙腈。丙烯腈、乙腈的色谱峰面积与吸附质量的线性相关系数均大于0.995。该法对实际空气样品中丙烯腈的检出限为5μg/m3,乙腈的检出限为10μg/m3,加标回收率均大于90%。     

Study on Preferential Solvation of Water by Electrochemical Method

The preferential solvation of water plays an important role in ferrocene research which is a subject of current interest. Voltammetric investigations were carried out for Au electrode in acetonitrile/water, showing preferential solvation of water. In our work, the preferential solvation of water in acetonitrile/water was studied by electrochemical methods including cyclic volitammetry, electrochemical impedance spectra and double‐step chronoamperometry. Ferrocenemethanol (FcCH₂OH) molecules as a solute spontaneously adsorb on the electrode surface in anhydrous acetonitrile, resulting from acetonitrile molecules tend to form an acetonitrile solvent layer on the surface of the electrode and acetonitrile solvent layer has a lower energy barrier than the aqueous solvent layer, which has been obtained by modeling solvation. The solvent strongly influences electrochemical behavior of solute. Once there is an amount of water in acetonitrile solvent, FcCH₂OH that adsorbed on the electrode surface desorb. This is because water preferentially solvate with FcCH₂OH in term of intermolecular forces between solvent and solute. Moreover, hydrogen bond between water molecules and FcCH₂OH molecules is stronger than dipole‐dipole interaction between acetonitrile molecules and FcCH₂OH molecules in solvation effect. Through electrochemical behavior of FcCH₂OH changing, preferential solvation of water is analyzed by electrochemical methods.     

Kinetics of underpotential deposition and nucleation of copper on the Pt(111) face in the presence of acetonitrile

The kinetics of underpotential deposition, three-dimensional nucleation, and growth of copper deposits at cathodic overpotentials on a Pt(111) electrode in solutions containing 0.5 M H₂SO₄, 10 mM CuSO₄, and 0–200 mM acetonitrile (AcN) is studied by the cyclic voltammetry, potentiostatic current transients, and scanning probe microscopy methods. At low volume concentrations of acetonitrile ([AcN] ≤ 4 mM), adsorbed acetonitrile molecules accelerate the formation of a co-adsorption lattice of copper adatoms with anions due to local electrostatic effects at the charged interface. At higher concentrations, the underpotential deposition process is hampered, but the desorption of copper adatoms occurs at potentials more positive than those at low acetonitrile concentrations. This effect is attributed to a stabilizing action of acetonitrile molecules situated on the layer of copper adatoms and, in part, on platinum. At [AcN] = 0.4–40 mM, adsorbed acetonitrile molecules accelerate the growth of the bulk copper deposit, but the nucleation stage is hindered. The dependence of the copper amount on the deposition potential at [AcN] = 40 mM exhibits a maximum at 0.15–0.17 V. This effect was previously observed in weakly acid solutions (pH 1.7–3.0) containing no acetonitrile. The maximum rate of the deposit growth corresponds to an optimum number of crystallites (which is not too great) and an optimum distance between the growing centers in conditions of mixed kinetics “diffusion + electron transfer.” A substantial number of complexes Cu(I)-AcN forms at high acetonitrile concentrations.     

Determination of pKa values of organic bases in aqueous acetonitrile solutions using capillary electrophoresis

Capillary electrophoresis (CE) was used for the determination of ionisation constants (pKa) of a variety of organic bases in aqueous acetonitrile solutions over the range 0-60% (v/v) acetonitrile. These bases are used as test compounds in HPLC column evaluation, thus knowledge of their pKa in hydro-organic solutions is useful. The base pKa decreased with acetonitrile concentration and significant shifts from the aqueous pKa (up to -0.8) were found using 60% acetonitrile. The CE application was confirmed to be very suitable for fast and accurate pKa measurement in aqueous organic solutions.     

Comparison of retention of aromatic hydrocarbons with polar groups in binary reversed-phase high-performance liquid chromatography systems

The retention of aromatic hydrocarbons with polar groups has been correlated as log k1 versus log k2 for reversed-phase high-performance liquid chromatography systems with different binary aqueous mobile phases containing methanol, acetonitrile or tetrahydrofuran as modifiers. Distinct changes in separation selectivity have been observed between tetrahydrofuran and acetonitrile or methanol systems. Methanol and acetonitrile systems show lower diversity of separation selectivity. The changes in retention and selectivity of aromatic hydrocarbons with various polar groups between any two chromatographic systems with binary aqueous eluents (tetrahydrofuran vs. acetonitrile, tetrahydrofuran vs. methanol and methanol vs. acetonitrile) have been interpreted in terms of molecular interactions of the solute with especially one component of the stationary phase region, i.e. extracted modifier, and stationary phase ordering. The ordering of the stationary phase region caused by modifier type influences the chromatographic selectivity of solutes with different molecular shape.     

Re-examination of the Reactivity of N-Carboxy Amino Acid Anhydrides 1. Polymerisation of Amino Acid NCAs in Acetonitrile and in the Solid State in Hexane

Ring-opening polymerisation of N-carboxy anhydrides of γ-benzyl-L- glutamate, L-alanine and L-leucine by a primary amine initiator in acetonitrile and in hexane was examined, with care taken to avoid contamination by moisture. The polymerisation of amino acid NCAs initiated by butylamine in hexane proceeded in the crystalline state (solid state) because the NCA crystals did not dissolve in hexane. Although amino acid NCAs were believed to polymerise completely in acetonitrile, polymerisation of the amino acid NCAs in acetonitrile was found to stop at around 20% conversion. As resulting polypeptides did not dissolve in acetonitrile, the polymer terminals were considered to be occluded in the polymer precipitate. On the other hand, each amino acid NCA was much more reactive in the solid state in hexane than in acetonitrile. Especially, L-leucine NCA showed remarkable reactivity in the solid state. The reactivity in the solid state was explained with reference to the crystal structure.     

反相离子对色谱中有机溶剂浓度和离子对试剂浓度对保留值的影响

我们测定了氨基苯磺酸和氨基萘磺酸在反相离子对色谱中不同乙腈/水, 甲醇/水配比和离子对试剂浓度下的保留值,并把两种冲洗剂下的保留值和关系式lnk'=a+C~c~b中的参数a,C作线性关联,得到很好的相关性,这表明有机溶剂乙腈和甲醇对选择性并无显著的影响,但乙腈有更大的冲洗强度.证明关系式lnk'=A+Blnc~p+C~c~ b能较好地描述有机溶剂和离子对试剂浓度对保留值的影响, 但当离子对试剂浓度较高时该关系式不成立.同时提出了有机溶剂浓度和离子对试剂浓度"等同效应" 的概念     

Sum-frequency observation of solvent structure at model chromatographic interfaces: acetonitrile-water and methanol-water systems

The adsorption of methanol-D2O and acetonitrile-D2O solutions at model chromatographic interfaces (octadecylsiloxane and quartz) was studied using sum-frequency spectroscopy. Methanol did not adsorb at either interface in detectable quantities, while acetonitrile adsorbs at the octadecylsiloxane- and quartz-solution interfaces in a concentration-dependent manner and is well ordered at the interface. Adsorption of acetonitrile was decreased by the addition of KCl at 10 and 100 mM. Acetonitrile adsorption was also observed during simulated gradient elution, demonstrating that adsorption of acetonitrile occurs on a time scale relevant to actual chromatographic separations. Examination of the OH stretch spectra of acetonitrile-H2O and methanol-H2O solutions at the interface revealed concentration-dependent changes in the acetonitrile-H2O spectra that are consistent with hydrogen bonding between interfacial water and acetonitrile, indicating that interfacial water is involved in mediating acetonitrile adsorption. The OH stretch spectra of methanol-H2O solutions showed no such changes.     

Effect of organic solvent on the crystal structure of Concanavalin A

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The ionic conductivity and catalyst activity effects of acetonitrile on proton exchange membrane fuel cells

The effect of trace levels of acetonitrile, an airborne pollutant, on proton exchange membrane fuel cells (PEMFCs) membrane/electrode assemblies (MEAs) was investigated in situ and ex situ using electrochemical impedance spectroscopy, cyclic voltammetry and polarization with a fuel cell and a membrane conductivity cell. In situ test results indicate that acetonitrile depresses electrode activity and decreases MEA ionic conductivity. Ex situ tests demonstrate that acetonitrile does not affect the membrane ionic conductivity, indicating the role for an acetonitrile reduction product (ammonium cation).     

STUDY OF THE ADSORPTION OF HUMAN SERUM ALBUMIN ON REVERSED-PHASE SUPPORTS.

This work examines the adsorption of Human Serum Albumin (HSA) on a Reversed-Phase High Performance Liquid Chromatographic (RPLC) support. The adsorption experiments were performed by frontal analysis. Adsorption isotherms were determined in pure buffer and in the presence of acetonitrile. Saturation is always reached, even at the lower protein concentrations. In view of the pore size of the particles (80 Å), it is assumed that HSA is adsorbed on the external surface of silica

In presence of acetonitrile, a variability in the amount of HSA adsorbed is found showing a maximum at 25% of acetonitrile. Slower adsorption kinetics are observed when the concentration of the organic modifier in the eluent is increased. The reversibility of HSA binding to the surface was investigated by desorbing the protein with 40% acetonitrile. The amount of HSA irreversibly adsorbed depends upon the experimental conditions used during the adsorption step. It is at a maximum when HSA is adsorbed with 25% acetonitrile. As the temperature is raised and only in the presence of acetonitrile, an important increase of the amount of HSA irreversibly adsorbed is observed.