农、兽药及工业化学物残留量分析中样品前处理微量化学法技术研究

建立了一种用于残留物分析样品处理的微量化学法(MICCM)体系,提出了该体系的基本概念、原理、单元操作,选择了一套基本系列设备和器具,并将这一体系用于检测不同样品中的农药、兽药、工业化学物残留量及食品添加剂。实例中,各方法检测限、回收率、变异系数的实验数据均达到了国际上对残留量分析方法的技术要求。该体系与经典常量化学法(MaCCM)样品处理体系相比,具有快速、简便、工效高,节省人力、试剂材料、能源以及占用场地小等多种优点。残留物分析可广泛用该体系取代经典法样品处理体系。     

高温比热容测试常见问题及误差分析

介绍了同步热分析仪(STA449F3)测试高温比热容过程中的常见问题及误差分析. 采用差示扫描量热三步法测试高温比热容. 试验结果表明, 提高仪器的稳定性和升温速率可减小比热测试值与理论值之间的误差. 此外, 将常规一段升温测试分割成若干个窄温区间, 提高了高温比热容测试的准确性.     

咖啡因、茶碱和氨茶碱的低温热容和热分析

咖啡因、茶碱和氨茶碱是临床应用中广泛使用的三种重要的甲基化的黄嘌呤.采用绝热量热、热重分析(TG)和差示扫描量热法(DSC)研究了这三种药物的热力学性质.采用绝热量热法测定了β型-咖啡因、茶碱和氨茶碱在80-370K温度范围内的摩尔热容值,结果显示氨茶碱的摩尔热容值最大,茶碱的摩尔热容值最小.采用最小二乘法对这三种药物热容的测量值和温度进行了拟合,得到了热容与折合温度的多项式,计算了咖啡因、茶碱和氨茶碱在298.15K时的热容分别为226.49、218.13和554.78J·K-1·mol-1;并计算了它们相对于298.15K时的焓和熵.采用热综合分析仪对这三种药物的热稳定性进行了评价,结果表明它们的热稳定顺序为氨茶碱咖啡因茶碱.通过DSC分析,得到了咖啡因和茶碱的相转变温度、相转变焓和熵.基于密度泛函理论的第一性原理,计算了咖啡因和茶碱分子的结构稳定性,结果显示咖啡因分子的稳定性低于茶碱,与实验结果吻合.     

仪器分析中的定量方法

在目前国内使用的仪器分析教材中,当介绍每一种仪器分析方法的应用时,均要涉及到它的定量分析方法。与经典的化学分析不同,除少数仪器方法(如:库仑分析、电重法、热分析等)外,一般都需要有与待测物质相同的标准样品,并以如下关系式为基础进行定量分析:     

热分析联用技术在高分子材料热性能研究中的应用

主要综述了热重-傅里叶变换红外(TG-FTIR)、裂解-色谱/质谱(Py-GC/MS)以及热重-质谱(TG-MS)三种常见的热分析联用技术的测试方法、原理,近几年这几种方法在高分子材料热性能研究中的应用进展和成果表明它们为材料的热分解过程和机理的探索提供了切实可行的研究方法,文章最后还展望了这些方法在热分析技术发展中的重要前景。     

陆英提取物乌索酸的热分析研究

用差示扫描量热法(DSC)和热重-微分热重法(TG-DTG)对静态空气气氛的乌索酸进行了热分析研究,为热分析鉴别乌索酸提供了实验依据.结果表明,加热到251℃时质量损失约3.31%,251～341 ℃时质量损失约68.09%,341～464 ℃时质量损失约27.70%,到464℃时质量仅余约0.90%.在158、311、415℃分别有3个放热峰.     

精密滴定量热计的改进及联机

LKB8700精密量热系统的滴定量热计是用于常量的量热测定,反应器是进口的玻璃容器。加热器、温度计、滴定管均装在反应器内,不便装样和清洗,滴定液进口只有一个,三种液体的混合只能分步滴定,热敏电阻随温度的变化用惠斯登电桥测量。针对快速反应手动跟踪较为困难这一情况,特别是为了研究油田应用的油-水-表面活性剂三元体系或多元体系,我们设计和建立了图1所示不锈钢制反应器,并在桥路输出中与微机相联接(图2),实     

槐米总黄酮提取物的热分析指纹图谱

以芦丁标准品作对照,应用热重法(TG)和微商热重法(DTG)对不同提取方法(碱提酸沉法、乙醇回流法和超声辅助法)以及提取条件(碱提取液pH值、稳定剂种类)下制备的槐米总黄酮提取物进行热重分析及热特征图谱解析。结果表明,由于提取方法和条件不同,产品质量有明显区别,反映在TG-DTG曲线上,表现出不同峰形、峰位及失重情况。在碱提酸沉法提取中,碱提取液pH=9,硼砂作稳定剂时,提取物的产率和含量均较高,而且其TG-DTG曲线特征与芦丁标准品比较接近。因此这些热分析图谱可以作为控制槐米总黄酮提取物质量的指纹图谱。     

组氨酸锌配合物生成反应的热动力学研究

用微量量热法对醋酸锌与组氨酸在水中的反应进行了热动力学研究。通过实验和计算得出了该反应的热动力学参数 (活化焓、活化熵、活化自由能 )、速率常数和三种动力学参数 (活化能、指前因子及反应级数 )。并对温度改变对该反应的影响及配合物的合成条件进行了讨论。     

高氮含能配合物[Co(AZT)_2(H_2O)_4](HTNR)_2·4H_2O的合成、晶体结构及性质

合成了新型含能配合物[Co(AZT)2(H2O)4](HTNR)2·4H2O(AZT=3-叠氮-1,2,4-三唑,HTNR=酸式三硝基间苯二酚),并用元素分析(EA)和傅立叶变换红外光谱(FT-IR)对其进行了表征.采用缓慢蒸发溶剂法培养得到配合物单晶,用X射线单晶衍射仪进行了结构测定,该晶体属于三斜晶系,空间群为P1,晶胞参数:a=7.1824,b=10.1812,c=13.115,α=98.046°,β=105.367°,γ=104.103°,V=875.23,Z=1.采用差示扫描量热分析(DSC)和热重-微分热重分析(TG-DTG)研究了目标配合物的热分解过程,结合分解产物的红外光谱分析,提出了其热分解机理.用Kissinger,Starink和Ozawa三种多重扫描速率方法对第一放热分解过程的非等温动力学进行了分析,求得的活化能分别为124.53,124.82和125.55kJ·mol-1,三种方法求得的活化能数据平行性好.测定了标题化合物的感度性质,结果表明标题化合物具有一定的摩擦感度.     

高温下渣熔融对煤焦-CO2气化反应特性的影响

在STA449F3型热天平上采用等温热重法研究了加入不同比例粗渣的煤焦在反应温度900～1380 ℃的气化反应性。利用热重-差示扫描量热法(TG-DSC)对煤焦的热行为进行分析,主要考察了加入不同比例粗渣、反应温度对煤焦反应性的影响。结果表明,煤焦-CO₂反应过程中,气化反应性和碳转化率可根据煤灰熔融流动温度分为相对低温段和高温段。在低温段,加入粗渣增加了煤焦的气化反应性和碳转化率;在高温段,加入粗渣会减小煤焦的碳转化率,并当粗渣加入量超过一定比例时,会降低煤焦的气化反应性。气化初期反应速率可根据粗渣熔融流动温度分为低温区域的化学反应控制和高温区域的扩散控制。     

煤及其拔头半焦的燃烧反应特性研究

采用热天平研究了贵州褐煤、三江原煤及其拔头半焦的燃烧行为,考察了粒径和升温速率对样品着火点和燃烧稳定性的影响。减小样品的粒径可显著降低样品的着火点,改善样品的燃烧性能,在粒径100～120目和升温速率25℃/min下,样品的燃烧稳定性最好。根据Coats-Redfern方法求解燃烧反应动力学参数。燃烧反应动力学分析表明,三种样品的热天平燃烧反应均为一级反应,并得到了实验样品的燃烧反应动力学参数,表观活化能E和指前因子A。贵州褐煤的活化能为100.0～163.6 kJ/mol,三江原煤的活化能为73.4～161.2 kJ/mol,三江煤焦的活化能为68.3～178.1 kJ/mol。     

Characterization of hydraulic mortars by means of simultaneous thermal analysis

The properties of hydraulic mortars were studied by means of simultaneous thermal analysis (STA), according to a procedure proposed in the literature. Hydraulic limes, cement and/or slaked lime were mixed using different proportions of both inert and reactive aggregates, in order to test the effectiveness of such procedure in distinguishing the different degree of hydraulicity of such samples. The use of the normalized coordinates suggested in the literature results in overlapping of the clusters of different kinds of mortars. Modified coordinates are proposed, which give promising results in view of outlining a ‘master curve’ of hydraulicity.     

污泥与煤和煤矸石共燃特性研究

利用STA 409 PC型同步热分析仪,对煤、煤矸石和污泥不同质量比样品的燃烧过程进行了热重分析。结果表明,单一煤和煤矸石的DTG曲线都只有一个明显的失重峰,污泥的DTG曲线有两个明显的失重峰,而混合物的DTG曲线都有两个失重峰。通过分析不同样品的混燃过程,发现随着煤所占质量比的增加,最大失重峰速率所对应的温度都有所降低。煤、煤矸石、污泥及其混合物的活化能为16.93kJ/mol～109.89kJ/mol。随着污泥所占质量比的增加,混合物的着火温度有所降低,当达到70%时,污泥与煤混合物的着火点接近单一污泥的着火点。     

A novel direct coupling of simultaneous thermal analysis (STA) and Fourier transform-infrared (FT-IR) spectroscopy

Evolved gas analysis (EGA) from thermal analyzers such as thermogravimetry (TG) or simultaneous thermal analysis (STA) which refers to simultaneous TG–DSC is well established since it greatly enhances the value of TG or TG–DSC results. The sensitive and selective FT-IR technique is in particular useful for the analysis of organic molecules but also for infrared active permanent gases evolved during most decomposition processes. The coupling interface between thermal analyzers and FT-IR spectrometers usually consists of heated adapters and a flexible, heated transfer line. In this work, a novel direct coupling of an STA instrument and an FT-IR spectrometer without a transfer line is presented. A very small FT-IR spectrometer is directly mounted on top of the STA furnace leading to a compact and fully integrated STA–FT-IR coupling system. The possibilities and the value of simultaneous STA–FT-IR measurements are demonstrated for organic, biomass, and ceramic samples in the temperature range between room temperature and about 1,500 °C. Various samples from the field of inorganics and organics—especially polymers—were furthermore measured showing the advantages of the direct STA–FT-IR coupling compared to state-of-the-art STA–FT-IR coupling using a heated transfer line: we found that the time delay caused by the volume of the transfer line itself is rather negligible whereas a significantly better correlation between gas detection and TG results was observed in case of some highly condensable decomposition gases. Aspects of quantification of evolved gases are furthermore discussed as well as the known nonlinearity of FT-IR detection at higher gas concentrations.     

Spherical tensor analysis of nuclear magnetic resonance signals

In a nuclear magnetic-resonance (NMR) experiment, the spin density operator may be regarded as a superposition of irreducible spherical tensor operators. Each of these spin operators evolves during the NMR experiment and may give rise to an NMR signal at a later time. The NMR signal at the end of a pulse sequence may, therefore, be regarded as a superposition of spherical components, each derived from a different spherical tensor operator. We describe an experimental method, called spherical tensor analysis (STA), which allows the complete resolution of the NMR signal into its individual spherical components. The method is demonstrated on a powder of a (13)C-labeled amino acid, exposed to a pulse sequence generating a double-quantum effective Hamiltonian. The propagation of spin order through the space of spherical tensor operators is revealed by the STA procedure, both in static and rotating solids. Possible applications of STA to the NMR of liquids, liquid crystals, and solids are discussed.     

Polyoxometalates-engineered hydrogen generation rate and durability of Pt/CNT catalysts from ammonia borane

Heterogeneously catalyzed hydrolytic dehydrogenation of ammonia borane is a remarkable structure sensitive reaction. In this work, a strategy by using polyoxometalates(POMs) as the ligands is proposed to engineer the surface and electronic properties of Pt/CNT catalysts toward the enhanced hydrogen generation rate and durability. Three kinds of POMs, i.e., silicotungstic acid(STA), phosphotungstic acid(PTA)and molybdophosphoric acid(PMA), are comparatively studied, among which the STA shows positive effects on the catalytic activity and durability. A catalyst structure-performance relationship is established by a combination of kinetic and isotopic analyses with multiple characterization techniques, such as HAADF-STEM, EDS, Raman spectroscopy and XPS. It is shown that the STA compared to the other two POMs can increase the Pt binding energy and thus promote the reaction. The insights demonstrated here could open a new avenue for boosting the reaction by employing the POMs as the ligands to engineer the catalyst electronic properties.     

Molecular assembly and photophysical properties of quaternary molecular hybrid materials with chemical bond

In this paper, two long chain aliphatic carboxylic acids (oleic acid [OLA] and stearic acid [STA]) are modified with cross-linking molecules (N-2-aminoethyl-3-aminopropyl-methyl-dimethoxylsiliane, (AEAPMMS, H(2) N(CH(2))(2)HN(CH(2))(3)SiCH(3)(OCH(3))(2) and 3-aminopropyl-methyl-diethoxylsiliane (APMES, H(2) N(CH(2))(3)SiCH(3)(OC(2)H(5))(2)) resulting in four new kinds of structural molecular bridge OLA (STA)-AEAPMMS (APMES). Subsequently, ternary molecular complex systems with four molecular bridges OLA (STA)-AEAPMMS (APMES) and 2,2-bipyridyl (bipy) of lanthanides (terbium and europium) or zinc ions were assembled, which resulted in four novel kinds of quaternary molecular hybrid materials (named as bipy-Ln (Zn)-OLA (STA)-AEAPMMS (APMES) with strong chemical bonds (N-Ln(Zn)-O coordination bonds and Si-O covalent bonds) after a sol-gel (cohydrolysis and copolycondensation) process of the modified molecular bridges (as structural ligand) with inorganic precursor (tetraethoxysilane, TEOS). And especially bipy behaves as functional ligand to sensitize the luminescence of terbium or europium ions through the effective intramolecular energy transfer process, which gives rise to the characteristic emission of metal ions. The design and assembly from structural and functional ligands can help achieve a candidate technology for molecular hybrids.     

一种煤与两种城市污水污泥混合热解的热重分析

采用热重分析法对一种煤和两种城市污水污泥（S1和S2）及其混合物进行了热解实验研究,揭示了煤和污泥在氮气中的热解特性及污泥对煤热解特性的影响。煤和污泥的热解特性参数不同,主要表现在总失重率、失重速率及挥发分析出温度区间等。煤与污泥S1混合有助于增加样品的热解总失重率,提高失重速率;污泥S1与煤的挥发分析出区间部分重合,污泥灰中含的无机物对煤的热解起到催化效果;煤和S2污泥混合后热解反应过程中无明显相互作用;煤与城市污水污泥混合物的相互作用与样品特性和混合比例有关。     

煤沥青的电化学加氢──Ⅰ．原料煤沥青的预处理和组成结构分析

为选择适于作为碳纤维原料的煤沥青，对三种中低温煤沥青的预处理和组成结构进行了研究，同时对其中的太钢煤沥青进行了热缩聚制取中间相沥青的结构变化分析。研究分析结果表明，只要经过合适的工艺路线进行处理，这三种煤沥青都有可能作为沥青基碳纤维的原料。