Retention behaviors of novel ionic liquid stationary phases and their selectivity for capillary gas chromatography

<正>One chloride-terminated ionic liquid(CTIL) and two hydroxyl-terminated ionic liquids(HTILs) were synthesized and used as stationary phases for capillary gas chromatography(CGC).Molecular interactions of these stationary phases were evaluated by Abraham solvation parameter model,indicating that the CTIL exhibits remarkably strong H-bond basicity and the HTILs possess both H-bond basicity and acidity.The molecular interactions were further confirmed by separation of a complex mixture consisting of ketones,aldehydes,esters,alcohols and aromatic compounds.It was found that the obtained solvation parameters correlate well with the chromatographic performances of the analytes in terms of elution order and resolution.The well correlated relationship between the solvation parameters and the selectivity of the CTIL and HTILs stationary phases is quite helpful in predicting and understanding the retention behaviors of different types of analytes on these stationary phases.     

Synthesis, spectroscopic and electrochemical property of an unsymmetrical porphyrin and its Zn compound

<正>In this article,a new 5-(p-maleicaminophenyl)-10,15,20-triphenylporphyrin(H_2P) and relative zinc compound(ZnP) were synthesized and characterized by means of elemental analyses,UV-vis,IR,MS and ~1H NMR spectroscopies.Furthermore,we have investigated the fluorescence spectroscopy of these compounds.The oxidation and reduction properties of the compounds were studied by the cyclic voltarnmetry,the oxidation-reduction potentials were obtained.     

化学法快速测定铁基非晶合金中硼含量的试样分解方法研究

用化学法测定铁基非晶合金中硼元素时,因合金试样难溶性及硼的某些特性,存在试样分解难的问题。利用H2O2强氧化性及硼既溶于酸又溶于碱的性质,通过试验确定了用H2O2(30%)与HCl(密度约1.19g/mL)分解试样,试样溶解完全。将该方法用于测定硼质量分数大于0.5%的铁基非晶合金中的硼,测定结果与ICP-AES法测定结果相符,测定结果的相对标准偏差小于1.5%(n=10)。     

胶粘剂拉伸剪切强度测量结果的不确定度评定

依据GB/T 7124-2008《胶粘剂拉伸剪切强度的测定》,以环氧树脂结构胶为例,对胶粘剂拉伸剪切强度测量结果的不确定度分量进行了分析和量化,计算了合成标准不确定度和扩展不确定度。当环氧树脂结构胶的拉伸剪切强度为28.8 MPa时,扩展不确定度为1.0 MPa(k=2)。     

催化剂载体对硼氢化钠在纳米金电极上电氧化行为的影响

分别以中孔炭(MPC)和VXC-72R炭黑作载体,制备了中孔炭载纳米Au粒子(Au/MPC)和VXC-72R炭黑载纳米Au粒子(Au/CB),并将其用作直接硼氢化钠燃料电池阳极电氧化催化剂.分别用X-射线衍射(XRD)、透射电镜(TEM)等比较了不同载体催化剂的结构和形貌.结果表明,纳米Au粒子均为面心立方结构,Au/MPC中纳米Au粒子的粒径为16nm左右比Au/CB中的纳米Au粒子的更小,且均匀分散在载体的表面.用循环伏安曲线和动电位极化曲线等比较了不同载体催化剂的电化学特性.结果表明,Au/CB的电流密度为38.10mA·cm-2,而Au/MPC的电流密度达到42.88mA·cm-2,比Au/CB的电流密度提高了12.5%.     

圆盘状a-Co(OH)2的控制合成及其电化学性能

采用AAO模板及后处理方法合成了圆盘状a-Co(OH)2并研究了其电化学电容性能.在该合成方法中,先采用阳极氧化铝模板结合交流电沉积的方法获得钴纳米线,而后将其在碱液中通过溶解氧氧化生成终端产物.用红外光谱(FT-IR),X射线衍射(XRD)和场发射扫描电子显微镜(FE-SEM)表征了产物的结构和形貌;用循环伏安、恒电流充放电测试方法对其电化学性能进行了测试.此外,对圆盘状Co(OH)2的形成机理进行了初步探讨.结果表明,用此方法合成的Co(OH)2具有圆盘状形貌,属a相态,且表现出较好的电容特性.     

Humidity responsive asymmetric free-standing multilayered film

A humido-responsive free-standing film has been created using layer-by-layer assembly technique. Polyethylenimine (PEI) at high pH was assembled with poly(acrylic acid) (PAA) at low pH on a Teflon substrate to yield a micro-nanostructured surface that can be made superhydrophobic after being coated with a low surface energy compound. The resulting asymmetric free-standing film with one surface being superhydrophobic while the other is hydrophilic after detachment from the substrate can undergo reversible bending/unbending shape transitions when the environmental humidity is changed. The bending/unbending movement of the free-standing film can be ascribed to the different responses of these two surfaces to humidity.     

A Time‐Resolved Spectroscopic Study of the Bichromophoric Phototrigger 3′,5′‐Dimethoxybenzoin Diethyl Phosphate: Interaction Between the Two Chromophores Determines the Reaction Pathway

3′,5′‐Dimethoxybenzoin (DMB) is a bichromophoric system that has widespread application as a highly efficient photoremovable protecting group (PRPG) for the release of diverse functional groups. The photodeprotection of DMB phototriggers is remarkably clean, and is accompanied by the formation of a biologically benign cyclization product, 3′,5′‐dimethoxybenzofuran (DMBF). The underlying mechanism of the DMB deprotection and cyclization has, however, until now remained unclear. Femtosecond transient absorption (fs‐TA) spectroscopy and nanosecond time‐resolved resonance Raman (ns‐TR³) spectroscopy were employed to detect the transient species directly, and examine the dynamic transformations involved in the primary photoreactions for DMB diethyl phosphate (DMBDP) in acetonitrile (CH₃CN). To assess the electronic character and the role played by the individual sub‐chromophore, that is, the benzoyl, and the di‐meta‐methoxybenzylic moieties, for the DMBDP deprotection, comparative fs‐TA measurements were also carried out for the reference compounds diethyl phosphate acetophenone (DPAP), and 3′,5′‐dimethoxybenzylic diethyl phosphate (DMBnDP) in the same solvent. Comparison of the fs‐TA spectra reveals that the photoexcited DMBDP exhibits distinctly different spectral character and dynamic evolution from those of the reference compounds. This fact, combined with the related steady‐state spectral and density functional theoretical results, strongly suggests the presence in DMBDP of a significant interaction between the two sub‐chromophores, and that this interaction plays a governing role in determining the nature of the photoexcitation and the reaction channel of the subsequent photophysical and photochemical transformations. The ns‐TR³ results and their correlation with the fs‐TA spectra and dynamics provide evidence for a novel concerted deprotection–cyclization mechanism for DMBDP in CH₃CN. By monitoring the direct generation of the transient DMBF product, the cyclization time constant was determined unequivocally to be ≈1 ns. This indicates that there is little relevance for the long‐lived intermediates (>10 ns) in giving the DMBF product, and excludes the stepwise mechanism proposed in the literature as the major pathway for the DMB cyclization reaction. This work provides important new insights into the origin of the 3′,5′‐dimethoxy substitution effect for the DMB photodeprotection. It also helps to clarify the many different views presented in previous mechanistic studies of the DMB PRPGs. In addition to this, our fs‐TA results on the reference compound DMBnDP in CH₃CN provide the first direct observation (to the best of our knowledge) showing the predominance of a prompt (≈2 ps) heterolytic bond cleavage after photoexcitation of meta‐methoxybenzylic compounds. This provides insight into the long‐term controversies about the photoinitiated dissociation mode of related substituted benzylic compounds.     

Variable-weighted least-squares support vector machine for multivariate spectral analysis

Multivariate spectral analysis has been widely applied in chemistry and other fields. Spectral data consisting of measurements at hundreds and even thousands of analytical channels can now be obtained in a few seconds. It is widely accepted that before a multivariate regression model is built, a well-performed variable selection can be helpful to improve the predictive ability of the model. In this paper, the concept of traditional wavelength variable selection has been extended and the idea of variable weighting is incorporated into least-squares support vector machine (LS-SVM). A recently proposed global optimization method, particle swarm optimization (PSO) algorithm is used to search for the weights of variables and the hyper-parameters involved in LS-SVM optimizing the training of a calibration set and the prediction of an independent validation set. All the computation process of this method is automatic. Two real data sets are investigated and the results are compared those of PLS, uninformative variable elimination-PLS (UVE-PLS) and LS-SVM models to demonstrate the advantages of the proposed method.     

Quantitative analysis of levodopa, carbidopa and methyldopa in human plasma samples using HPLC-DAD combined with second-order calibration based on alternating trilinear decomposition algorithm

An HPLC method combined with second-order calibration based on alternating trilinear decomposition (ATLD) algorithm has been developed for the quantitative analysis of levodopa (LVD), carbidopa (CBD) and methyldopa (MTD) in human plasma samples. Prior to the analysis of the analytes by ATLD algorithm, three time regions of chromatograms were selected purposely for each analyte to avoid serious collinearity. Although the spectra of these analytes were similar and interferents coeluted with the analytes studied in biological samples, good recoveries of the analytes could be obtained with HPLC-DAD coupled with second-order calibration based on ATLD algorithm, additional benefits are decreasing times of analysis and less solvent consumption. The average recoveries achieved from ATLD with the factor number of 3 (N = 3) were 100.1 ± 2.1, 96.8 ± 1.7 and 104.2 ± 2.6% for LVD, CBD and MTD, respectively. In addition, elliptical joint confidence region (EJCR) tests as well as figures of merit (FOM) were employed to evaluate the accuracy of the method.