不可忽视的“化学实验教学设计”

化学实验在科学研究和化学学习中有着重要作用,化学实验教学设计意在教学理论的指导下,对实验的目标进行分解、实验内容进行改进与组合、实验过程进行优化、实验的效果进行评价。结合实施原则从3个方面对化学实验教学设计进行了探索。     

白酒年份检测鉴定技术研究进展

综述了白酒年份检测鉴定技术,包括气相色谱法、气相色谱-质谱法、荧光光谱法以及稳定同位素质谱法等技术,并对上述几类方法进行了比较。以气相色谱为基础的分析技术,通过对白酒酒基中的挥发物成分进行分析并构建指纹图谱和预测模型,与实际样品谱图进行匹配进行年份测定;以稳定同位素为基础的分析技术,通过对存储过程中白酒酒基中放射性同位素¹⁴C等成分衰减程度来进行年份测定;以光谱为基础的分析技术,通过预测模型的构建和实际样品的匹配进行年份测定;电子鼻、电子舌检测技术更依赖于鉴定人员对于分析方法的熟练使用,以科学分析方法进行数据分析。最后对白酒年份检测鉴定技术的发展进行了展望。     

溴鎓离子的形成及其在有机化学中的应用

对烯烃和溴素形成溴鎓离子过程、加成的立体化学进行描述,对有机化学中的烯烃和溴素加成的立体专一性进行举例和解析,并对部分高校利用该理论进行考研题型的扩展进行讨论。     

一个异乎寻常的冷胀热缩的现象——关于“熵”的实验设计

本实验是针对选修4《化学反应原理》第四节“化学反应进行的方向”中关于“熵”的概念开发创设的一个演示和探究实验,它有助于学生的探索和理解。化学反应进行的方向是中学化学所涉及的概念之一,教材以学生熟悉的自发进行的放热反应为例,介绍化学反应能量降低具有自发进行的倾向,再以生活现象为例,说明混乱度增加是自然界的普遍规律,是化学反应自发进行的另一种倾向。     

综合设计性实验:食品添加剂甘氨酸钠碳酸盐的合成及性质初探

介绍一个综合设计性实验——食品添加剂甘氨酸钠碳酸盐的合成及性质初探。学生查阅文献,设计实验方案,采用湿法、超声法、微波法合成甘氨酸钠碳酸盐并对合成方法进行比较,学习使用红外和紫外大型分析仪器对产物进行表征,并对产物的性质进行了初步探讨,最后总结实验结果,进行答辩,完整地进行了一次简单的科研实践过程。     

水合肼在还原制备苯胺类化合物中的专利技术进展

从专利角度出发,对水合肼作为还原剂,硝基苯类化合物还原制备苯胺类化合物的方法进行综述。对水合肼还原制备硝基苯的专利申请情况、主要申请人的申请情况进行了分析,对镍、钯、铁以及活性炭等催化剂在水合肼还原制备苯胺类化合物中的应用进行归纳和总结,且对活性炭作为催化剂的反应进行了概述,且对其发展趋势进行了展望。     

锆氢化反应研究I.酯类及双官能团化合物的锆氢化反应

本工作以一氯一氢二茂锆为还原试剂,对苯甲酸乙酯和苯甲酸甲酯进行还原,对还原的条件及水解产物的分离鉴定进行了研究。并对同时含酯基与其它官能团的几种化合物进行了选择性还原,列出了官能团还原先后的顺序,对结果进行了讨论。     

novAA400P石墨炉原子吸收光谱仪常见故障分析、处理和日常维护要求

对novAA400P石墨炉原子吸收光谱仪常见故障进行了分析总结,并结合应用实践给出了处理方法,可以快速准确地进行故障的处理,保证检测工作的顺利进行,同时对石墨炉原子吸收的日常维护进行了介绍.     

快速傅立叶变换用于色谱噪声平滑及微弱信号的检测

应用快速傅立叶变换法（ＦＦＴ）对色谱噪声进行平滑处理及微弱信号检测,同时,也与其他数字滤波法进行了比较。结果表明,利用ＦＦＴ法可以很好地对噪声进行平滑处理,使信噪比提高１８倍,为更好地进行痕量组分的色谱微弱信号检测打下了基础。     

GD-MS法和ICP-MS法测定高纯铌中痕量元素

采用辉光放电质谱法(GD-MS)对高纯铌中Ta,Mo,W等痕量杂质元素进行了测试,并对GD-MS工作参数进行了优化,部分元素与采用电感耦合等离子体质谱法(ICP-MS)定量分析的结果进行比较,对某些元素含量差别较大的原因进行了分析,论述了Element GD辉光放电质谱仪的特点及其在痕量杂质分析上的优势。     

Rapid Chemical Reaction Monitoring by Digital Microfluidics‐NMR: Proof of Principle Towards an Automated Synthetic Discovery Platform

Microcoil nuclear magnetic resonance (NMR) has been interfaced with digital microfluidics (DMF) and is applied to monitor organic reactions in organic solvents as a proof of concept. DMF permits droplets to be moved and mixed inside the NMR spectrometer to initiate reactions while using sub‐microliter volumes of reagent, opening up the potential to follow the reactions of scarce or expensive reagents. By setting up the spectrometer shims on a reagent droplet, data acquisition can be started immediately upon droplet mixing and is only limited by the rate at which NMR data can be collected, allowing the monitoring of fast reactions. Here we report a cyclohexene carbonate hydrolysis in dimethylformamide and a Knoevenagel condensation in methanol/water. This is to our knowledge the first time rapid organic reactions in organic solvents have been monitored by high field DMF‐NMR. The study represents a key first step towards larger DMF‐NMR arrays that could in future serve as discovery platforms, where computer controlled DMF automates mixing/titration of chemical libraries and NMR is used to study the structures formed and kinetics in real time.     

NMR仪器温控系统测试与校正

介绍了一型自主研制的温控系统的原理与结构,采用核磁共振(NMR)实验测温方法检测了温控系统的精确性和稳定性.针对精确性进行了设计校正,校正后精确度达到了±0.2℃.指出了稳定性方面的特点与不足之处,提出改进意见.     

数字化矩形离子阱质谱仪的设计及性能

将数字化离子阱技术和矩形离子阱(RIT)技术相结合,建立了数字化矩形离子阱质谱仪.此技术和装置既具有数字化电源的结构简单、输出稳定和易精确控制等特点,又结合了矩形离子阱的高离子存储效率、结构简单以及加工和装配容易等优点.构建了基于电喷雾(ESI)电离源的数字化矩形离子阱质谱仪系统,并使用Fenfluramine和PPG2000分别对此系统的质量分辨率和质量范围进行了测试.研究结果表明:一个用印刷线路板(PCB)制作的简单矩形离子阱,在200 V(半峰值)的数字束缚电压的驱动下,获得了大于500的质量分辨率和超过2600 Th的质量范围.实验证明,数字化离子阱技术的应用可以显著提高矩形离子阱的性能,特别是质量范围等关键的质谱仪指标.     

Interfacing an analogue infrared spectrometer to a microcomputer

An Apple microcomputer has been interfaced to a Perkin-Elmer model 577 infrared spectrometer. The spectral data are digitized with the aid of an in-house designed 12-bit analogue-to-digital interface unit. Control and status signals are obtained from the spectrometer and an optical encoder unit is used to provide an accurate wavenumber marker for the conversion and data recording. The digital data are formatted by the microcomputer and then can be manipulated by programs already developed for handling spectral data recorded from digital spectrometers.     

Quantitative proton magnetic resonance determination of N,N‐dimethylformamide in one intermediate of the Quimi‐Hib vaccine

Quimi‐Hib is a conjugate vaccine against Haemophilus influenza type b (Hib) where the Hib antigen is the only one produced by chemical synthesis. NMR has become the alternative of choice for the identity of intermediates during the chemical synthesis of Hib antigen. We explore a rapid quantitative proton magnetic resonance (qHNMR) assay for the determination of N,N‐dimethylformamide (DMF) as a residual in one of the critical intermediates. The proposed assay has been shown to be accurate, precise for intermediate precision conditions (relative standard deviation <3% for spectrometer‐to‐spectrometer variations), specific (no detected interferences), and rugged (percentage difference <3% for day‐to‐day and spectrometer‐to‐spectrometer variations). The quantitative NMR assay can replace the common chromatographic methods for monitoring the DMF contents in one crucial step of the synthetic scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

Research on Dispersive Detection Technology Based on Digital Micromirror Device by Atomic Fluorescence Spectrometry

A ultraviolet (UV) digital micromirror spectrometer using a digital micromirror device (DMD) as a spatial light modulator, a grating as a spectroscope and a photomultiplier tube (PMT) as a detector, was specially designed for dispersive hydride generation atomic fluorescence spectrometry (HG-AFS). To improve the detection ability of the UV digital micromirror spectrometer for weak fluorescence signals at 180–320 nm, a high UV transmittance DMD was used and the signal acquisition system was improved, and the control parameters of DMD and PMT negative high voltage were optimized. The feasibility of the spectrometer was demonstrated with standard sample analyzing of As, Sb, Bi, and Hg, the emission and atomic fluorescence spectra were obtained, and the scattering interference caused by the light source was discussed. The results showed that the UV digital micromirror spectrometer had a preliminary ability for the excitation fluorescence analysis by HG-AFS. In addition, due to no macroscopic moving parts, the UV digital micromirror spectrometer had simple construction and fast analysis speed (0.848 s per spectrum scan).     

Parahydrogen-Induced Radio Amplification by Stimulated Emission of Radiation

Radio amplification by stimulated emission of radiation (RASER) was recently discovered in a low-field NMR spectrometer incorporating a highly specialized radio-frequency resonator, where a high degree of proton-spin polarization was achieved by reversible parahydrogen exchange. RASER activity, which results from the coherent coupling between the nuclear spins and the inductive detector, can overcome the limits of frequency resolution in NMR. Here we show that this phenomenon is not limited to low magnetic fields or the use of resonators with high-quality factors. We use a commercial bench-top 1.4 T NMR spectrometer in conjunction with pairwise parahydrogen addition producing proton-hyperpolarized molecules in the Earth's magnetic field (ALTADENA condition) or in a high magnetic field (PASADENA condition) to induce RASER without any radio-frequency excitation pulses. The results demonstrate that RASER activity can be observed on virtually any NMR spectrometer and measures most of the important NMR parameters with high precision.     

Solution-State 2D NMR Spectroscopy of Mixtures HyperpolarizedUsing Optically Polarized Crystals

The HYPNOESYS method (Hyperpolarized NOE System), which relies on the dissolution of optically polarized crystals, has recently emerged as a promising approach to enhance the sensitivity of NMR spectroscopy in the solution state. However, HYPNOESYS is a single-shot method that is not generally compatible with multidimensional NMR. Here we show that 2D NMR spectra can be obtained from HYPNOESYS-polarized samples, using single-scan acquisition methods. The approach is illustrated with a mixture of terpene molecules and a benchtop NMR spectrometer, paving the way to a sensitive, information-rich and affordable analytical method.     

Parahydrogen‐Induced Radio Amplification by Stimulated Emission of Radiation

Radio amplification by stimulated emission of radiation (RASER) was recently discovered in a low‐field NMR spectrometer incorporating a highly specialized radio‐frequency resonator, where a high degree of proton‐spin polarization was achieved by reversible parahydrogen exchange. RASER activity, which results from the coherent coupling between the nuclear spins and the inductive detector, can overcome the limits of frequency resolution in NMR. Here we show that this phenomenon is not limited to low magnetic fields or the use of resonators with high‐quality factors. We use a commercial bench‐top 1.4 T NMR spectrometer in conjunction with pairwise parahydrogen addition producing proton‐hyperpolarized molecules in the Earth's magnetic field (ALTADENA condition) or in a high magnetic field (PASADENA condition) to induce RASER without any radio‐frequency excitation pulses. The results demonstrate that RASER activity can be observed on virtually any NMR spectrometer and measures most of the important NMR parameters with high precision.     

Interpretation du Spectre RMN de l'Octaacetate de Cellobiose a 250 MHz. Application au Triacetate de Cellulose

Using a 250 MHz NMR spectrometer and double resonance experiments the full identification of the 14 cyclic protons of α octaacetate cellobiose has been performed. The results obtained here are of particular interest as affording an answer to the problem of the existence of particular signals in the NMR spectra of cellulose triacetate. These signals are both due to the anomeric extremity of the polymer.