扰流色谱体系的建立及基本原理

扰流色谱是国际上八十年代初出现的一种色谱新技术[1]．至今，国内尚未报导．扰流色谱技术作为一种物理化学测试手段，具有设备简单，操作方便，应用广，精度高等特点．它可进行表面催化反应动力学的研究和多种物理化学常数的测定，因此研究和建立我国的扰流色谱测试方法是色谱技术的延伸，是物理化学测试方法应开拓的领域．1扰流色谱装置扰流色谱实验装置示意图如图1．它由以下几部分组成：（1）一台具有高灵敏度检测器（如FID）的普通气相色谱仪．（2）取样柱．（3）扩散柱．（4）四通阀．（5）限流器．四通阀控制载气的流向，载气的转…     

A Study of Retention Time Gradient Effect of Gradientally Loaded Columns

In this work, the "retention time gradient effect" of gradient GC columns is intensively studied to establish some equations and formulas for structure calculation of chromatographic columns. In addition, the relevant computer programs are designed.     

Supported liquid membrane microextraction with high-performance liquid chromatography-UV detection for monitoring trace haloacetic acids in water

Supported liquid membrane microextraction (SLMME) with high-performance liquid chromatography (HPLC)-UV detection has been developed for the extraction, preconcentration, and determination of all the nine haloacetic acids (HAAs) in water. The HAAs are extracted into a supported liquid membrane, and then back-extracted into few microliters of an acceptor solution. The extract was directly analyzed by HPLC-UV with a 15-min run. Enrichment factors in the range of 300-3000 were obtained in a 60-min extraction, and detection limits were at low to sub-microg/L level with R.S.D. values between 1.5 and 10.8%. The parameters that affected analyte enrichment were studied. This approach offers an attractive alternative to the current US Environmental Protection Agency standard methods for HAA analysis, which require complex sample preparation and derivatization prior to analysis by gas chromatography. SLMME can also be used in conjunction with other analytical schemes, such as, ion chromatography and capillary electrophoresis.     

碳酸盐碳,氧稳定同位素微量测试方法的研究

本文简要叙述了微量碳酸盐样品碳，氧稳定同位素测试对于古海洋学研究的重要性，着重介绍了该方法的原理，制样过程以及质谱测量，同时还介绍了微量测试几个方面的试验工作，并对影响微量测试的几种因素进行了探讨。     

Single-molecule Michaelis-Menten equations

This paper summarizes our present theoretical understanding of single-molecule kinetics associated with the Michaelis-Menten mechanism of enzymatic reactions. Single-molecule enzymatic turnover experiments typically measure the probability density f(t) of the stochastic waiting time t for individual turnovers. While f(t) can be reconciled with ensemble kinetics, it contains more information than the ensemble data; in particular, it provides crucial information on dynamic disorder, the apparent fluctuation of the catalytic rates due to the interconversion among the enzyme's conformers with different catalytic rate constants. In the presence of dynamic disorder, f(t) exhibits a highly stretched multiexponential decay at high substrate concentrations and a monoexponential decay at low substrate concentrations. We derive a single-molecule Michaelis-Menten equation for the reciprocal of the first moment of f(t), 1/, which shows a hyperbolic dependence on the substrate concentration [S], similar to the ensemble enzymatic velocity. We prove that this single-molecule Michaelis-Menten equation holds under many conditions, in particular when the intercoversion rates among different enzyme conformers are slower than the catalytic rate. However, unlike the conventional interpretation, the apparent catalytic rate constant and the apparent Michaelis constant in this single-molecule Michaelis-Menten equation are complicated functions of the catalytic rate constants of individual conformers. We also suggest that the randomness parameter r, defined as <(t - )2> / t2, can serve as an indicator for dynamic disorder in the catalytic step of the enzymatic reaction, as it becomes larger than unity at high substrate concentrations in the presence of dynamic disorder.     

铑(Ⅲ)-溴酸钾-三氯偶氮氯膦催化分光光度法测定微量铑

铑（Ⅲ）在酸性介质中对溴酸钾氧化三氯偶氮氯膦的褪色反应有明显的催化作用。确定了最佳反应条件，建立了测定微量铑的催化分光光度新方法。铑在1．0～50．0μg／L范围内符合比耳定律，其表观摩尔吸光系数ε550＝1．08×106L·mol-1·cm-1。用于铂－铑催化剂中铑的测定，结果满意。     

Dendritic polyisophthalate endcapped with naphthyl groups for holographic recording

A novel dendritic polyisophthalate with 12 naphthyl groups at the chain ends was synthesized from 5‐hydroxyisophthalic acid as an AB₂ monomer, 1,3,5‐benzenetricarbonyl trichloride as an ‘initiator core’ molecule, and β‐naphthol as an endcapping reagent, via a stepwise growth process. An average molecular weight of 2860 g mol^?1, and a refractive index of 1.618 at 650 nm were obtained by gel permeation chromatography and ellipsometry, respectively. A photopolymerizable recording dry film incorporating this dendrimer as a polymeric binder was used for holographic recording. Diffraction gratings with diffraction efficiency exceeding 80%, together with a modulation index of 10^?2 were obtained. Copyright © 2004 John Wiley & Sons, Ltd.     

Selective detection of dopamine in the presence of ascorbic acid and uric acid by a carbon nanotubes-ionic liquid gel modified electrode

The electrochemistry of dopamine (DA) was studied by cyclic voltammetry at a glassy carbon electrode modified by a gel containing multi-walled carbon nanotubes (MWNTs) and room-temperature ionic liquid of 1-octyl-3-methylimidazolium hexafluorophosphate (OMIMPF₆). The thickness of gel on the surface of the electrode has to be controlled carefully because the charging currents increase with the modified layer being thicker. The anodic peaks of DA, ascorbic acid (AA) and uric acid (UA) in their mixture can be well separated since the peak potential of AA is shifted to more negative values, while that of UA is shifted to more positive values due to the modified electrode. At pH 7.08 the three peaks are separated ca. 0.20 and 0.15 V, respectively; hence DA can be determined in the presence of UA and more than 100 times excess of AA. Under optimum conditions linear calibration graphs were obtained over the DA concentration range 1.0 × 10⁻⁶ to 1.0 × 10⁻⁴ M. The detection limit of the current technique was found to be 1.0 × 10⁻⁷ M based on the signal-to-noise ratio of 3. The modified electrode has been successfully applied for the assay of DA in human blood serum. This work provides a simple and easy approach to selectively detect dopamine in the presence of ascorbic acid and uric acid.     

An extended stochastic response surface method for random field problems

An efficient and accurate uncertainty propagation methodology for mechanics problems with random fields is developed in this paper. This methodology is based on the stochastic response surface method (SRSM) which has been previously proposed for problems dealing with random variables only. This paper extends SRSM to problems involving random fields or random processes fields. The favorable property of SRSM lies in that the deterministic computational model can be treated as a black box, as in the case of commercial finite element codes. Numerical examples are used to highlight the features of this technique and to demonstrate the accuracy and efficiency of the proposed method. A comparison with Monte Carlo simulation shows that the proposed method can achieve numerical results close to those from Monte Carlo simulation while dramatically reducing the number of deterministic finite element runs. The project supported by the National Natural Science Foundation of China (10602036). The English text was polished by Yunming Chen.