差示扫描量热法测定对乙酰氨基酚原料药纯度

建立差示扫描量热(DSC)法测定对乙酰氨基酚原料药纯度的方法。考察升温速率、称样量、坩埚类型对测定结果的影响,确定最佳测定条件:升温速率为1.0℃/min,称样量为2.0~2.2 mg,选用Tzero密封铝坩埚作为样品盘。DSC法测定对乙酰氨基酚原料药纯度为99.91%,测定结果的相对标准偏差为0.03%(n=6),DSC法测定结果与紫外可见分光光度法测定结果(99.85%)基本一致,且DSC法测定结果的相对标准偏差较小。该方法简便、快速、准确,无需标准品,可用于对乙酰氨基酚原料药纯度的测定。     

差示扫描量热法测定比沙可啶的纯度

建立差示扫描量热法测定比沙可啶原料药样品纯度的方法。考察了炉体气氛、升温速率、称样量3个因素对差示扫描量热法测定结果的影响,确定差示扫描量热法最佳实验条件:升温速率为2.0 K/min,称样量为2.0~4.0 mg,炉内气体为静态空气。差示扫描量热法测定比沙可啶样品纯度为99.86%,测定结果的相对标准偏差为0.02%(n=6),差示扫描量热法测定比沙可啶样品纯度值与HPLC测定结果具有良好的一致性。该方法可以快速、准确地测定比沙可啶化学纯度,为比沙可啶纯度测定提供了一种新的分析方法。     

差示扫描量热法测定马来酸酐纯度

用差示扫描量热法（DSC）测定马来酸酐的纯度,测定条件为升温速率0．8℃／min,样品量2．6～2．8mg,氮气流速为40mL/min。纯度测定结果的相对标准偏差（RSD）为0．02％（n=5）。将DSC法、液相色谱法、药典法、滴定分析法对不同物质纯度的测定结果进行了比对,4种方法的测定结果基本一致。DSC法简便、快速、准确、重现性好,适合马来酸酐纯度的测定。     

甘露醇纯度的差示扫描量热法测定

使用差示扫描量热法(DSC)对甘露醇纯度进行测定。密封式铝坩埚封装样品,最佳实验条件为升温速率约0.7℃·min-1,样品量约2.5mg,氮气流速为20～40mL·min-1;纯度测定的RSD为0.016,纯度准确测定的下限为98%,通过F检验及t检验,该方法与药典法无显著差异。该方法简便、快速、准确,适合甘露醇等高纯度药品的纯度测定。     

差示扫描量热法测量纯度的不确定度分析

依据JJF1059-1999分析了差示扫描量热法测量纯度的不确定度。以美国PE公司的DSC-2C型差示扫描量热仪为例,该方法测量苯纯度的提高扩展不确定度为0.11%。     

几种缩聚耐热聚合物单体纯度的差示扫描量热(DSC)测定

利用差示扫描量热法测定了缩聚单体的纯度。对于一种新型聚芳醚砜的单体4,4′—二氯二苯砜的纯度在99.0和99.9mol%时,所得缩聚物的比浓粘度分别可达0.36和0.62。提出了适用于缩聚单体纯度DSC测定法的试验程序。采用封闭坩埚,该法可用于升温时有少量升华(或挥发)的单体的纯度测定。     

差示扫描量热法测定草酸艾司西酞普兰纯度

采用差示扫描量热法(DSC),根据DSC曲线利用纯度分析软件测定草酸艾司西酞普兰的纯度。对实验条件进行了优化,升温速率为4.0 K/min,称样量为2~3.2 mg。测得草酸艾司西酞普兰的纯度为99.17%,相对标准偏差为0.05%(n=6)。该法测定结果与非水滴定法测定结果(99.24%)基本一致。差示扫描量热法可用于测定草酸艾司西酞普兰纯度,方法操作简便、结果准确。     

示差扫描量热法进展及其在高分子表征中的应用

示差扫描量热法(DSC)是表征材料热性能和热反应的一种高效研究工具,具有操作简便、应用广泛、测量值物理意义明确等优点.近年来DSC技术的发展大大拓展了高分子材料表征的测试范围,促进了对高分子物理转变的热力学和动力学的深入研究.温度调制示差扫描量热法(TMDSC)是DSC在20世纪90年代的标志性进展,它在传统DSC的线性升温速率的基础之上引入了调制速率,从而可将总热流信号分解为可逆信号和不可逆信号两部分,并能测量准等温过程的可逆热容.闪速示差扫描量热法(FSC)是DSC技术近年来的创新性发展,它采用体积微小的氮化硅薄膜芯片传感器替代传统DSC的坩埚作为试样容器和控温系统,实现了超快速的升降温扫描速率以及微米尺度上的样品测试,使得对于高分子在扫描过程中的结构重组机制的分析以及对实际的生产加工条件的直接模拟成为可能.本文从热分析基础出发,依次对传统DSC、TMDSC和FSC进行了介绍,内容覆盖其发展历史、方法原理、操作技巧及其在高分子表征中的应用举例,最后对DSC未来的发展和应用进行了展望.本文希望通过综述DSC原理、实验技巧和应用进展,帮助读者加深对DSC这一常用表征技术的理解,进一步拓展DSC表征高分子材料的应用.     

差示扫描量热法对芝麻酚纯度标准物质的定值

建立了采用差示扫描量热法对芝麻酚纯度标准物质的定值及不确定度评价的数学模型、有效检测技术和分析方法.采用差示扫描量热法测量芝麻酚样品纯度的实验条件为升温速率3.0 K/min,称样量3.4～4.7 mg,炉内气体为静态空气.对通过均匀性检验和长期稳定性考察的芝麻酚纯度标准物质进行定值和不确定度评价,同时采用高效液相色谱...     

差示扫描量热法确定L-脯氨酸的热动力学参数

利用差动热分析仪测得L 脯氨酸的差示扫描量热分析(DSC)曲线,采用普适积分法和微分方程法通过逻辑选择确定了L 脯氨酸相变和热解过程的最可几机理函数,并计算出相应的指前因子和活化能.     

差示扫描量热仪对物质相变潜热的精确量度

差示扫描量热仪(DSC)在测量物质相变潜热方面有着十分广泛的应用。当相变前后试样的比热发生较大的变化,亦即相变前后DSC的基线不在同一直线上时,导致在实际测量样品的相变潜热过程中,出现各种经验处理方法共存的局面[1-3]。对于同一实验曲线,不同的经验处理方法会得到不同的潜     

Thermal Denaturation of Bacterial Cells Examined by Differential Scanning Calorimetry

Thermal stability of vegetative cells of Listeria monocytogenes, Escherichia coli and Lactobacillus plantarum was studied by counting viable fractions and determining DSC curves of their suspensions. DSC curves in the 5–99°C range showed a series of endothermic transitions between 50 and 60°C, where the heat destruction of cells occurred. Heat denaturation of DNA required a higher temperature than cell killing. Thermal death was strongly influenced by the pH, composition and NaCl content of the suspending buffer. A mathematical model developed by us enabled comparison of DSC peak temperatures and temperatures required for loss of viability.This revised version was published online in November 2005 with corrections to the Cover Date.     

用DSC研究稀土顺式聚丁二烯的低温结晶与熔融行为

采用示差扫描量热仪研究了稀土顺式聚丁二烯(PB)等温过程的结晶及其熔融行为. 结果表明,在等温结晶的后期存在晶型完善的过程,而且随着等温结晶温度的提高,结晶速率均下降. PB的熔融总是在比等温结晶温度高约2 ℃处开始,而且在10 ℃/min的升温速率下,DSC曲线不仅显示出很宽的熔融温度范围,而且在低温处还出现了小肩峰,说明等温结晶后体系中具有在该升温速率下不同稳定性的晶体. 通过不同温度下的等温结晶曲线,分别采用结晶度趋于零(Xc=0)时的熔点和结晶时间无限长(t-1c＝0)时的熔点,用Hoffman-Weeks方法得到顺式聚丁二烯的平衡熔点T∞m位于9～17.6 ℃之间.     

Physical Aging of Maltose Glasses as Measured by Standard and Modulated Differential Scanning Calorimetry

The physical aging characteristics of maltose glasses aged at two temperatures below the glass transition temperature, T_g, (T_g-10°C and T_g-20°C) from 5 to 10 000 min were measured by standard differential scanning calorimetry (SDSC) and modulated differential scanning calorimetry (MDSC). The experimentally measured instrumental T_g, the calculated T_g, and the excess enthalpy values were obtained for aged glasses using both DSC methods. The development of excess enthalpy as a function of aging time, as measured by both SDSC and MDSC, was fit using the Cowie and Ferguson and Tool-Narayanswamy-Moynihan models. The change in the T_g values and the development of the excess enthalpy resulting from physical aging measured by the two DSC methods are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study by Differential Scanning Calorimetry of Water-in-Oil Emulsions Stabilized by Clays and CTAB

In this work, we have tested various formulations in order to get emulsions containing pure water, Tunisian olive oil, Tunisian clays, and an ammonium salt. Two different types of clays: smectite and kaolinite and the cethyltrimethylamonium bromide (CTAB) were tested. CTAB is used as surfactant and a compound modifying the clays properties. The amount of CTAB being fixed at 0.66 w/w, the proportions of clays were varied from 0 to 9% for each of the following proportions of water: 10, 20, 30%. To the aqueous phase obtained by mixing two separate aqueous phases: water + CTAB and water + clay, the oil was added drop by drop, the agitation being maintained at 5000 rpm. The obtained mixtures were analyzed by Differential Scanning Calorimetry (DSC), optical microscopy and bottle tests. An optimized formulation containing water (30%), smectite clay (5.3%) and CTAB (0.66%) was found to give W/O emulsions which kinetic stability is greater than 75 days regarding coalescence and greater than 700 hours regarding sedimentation.     

Thermal Properties of Standard and Reference Humic Substances by Differential Scanning Calorimetry

Differential Scanning Calorimetry combined with Fourier transform infrared spectroscopy, was applied to the study of a number of fulvic and humic acids extracted from soils, peat, river and seawater. The thermal patterns obtained were related to the nature and origin of samples. The low-temperature endotherms were attributed to dehydration and loss of peripheral polysaccharide chains. The endotherm at 250°C observed for soil FA was ascribed to partial decarboxylation of more labile surface COOH groups, whereas the high-temperature exotherms at about 500°C were related to the degree of polycondensation of the aromatic network of the humic molecules.This revised version was published online in November 2005 with corrections to the Cover Date.     

Primary Transformation Rate Measurements Through Differential Scanning Calorimetry

Summary. The primary crystallization of molten alloy systems at high undercooling is studied by a precise quantitative analysis of the calorimetric signal obtained during the transformation in terms of the reaction rate under isothermal and continuous heating regimes. It is shown that, under specific conditions, namely, stoechiometric primary precipitates, generalized relationships for the crystallization enthalpy and the reaction rate may be obtained.