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。     

差示扫描量热法测定除草剂绿麦隆的纯度

研究了用差示扫描量热法(DSC)测定绿麦隆的纯度。该法测定最佳条件为升温速率0.5 K.min-1,样品量2~3 mg,保护气流速20 mL.min-1。用本法测得绿麦隆原药的纯度为98.35%,相对标准偏差(RSD)为0.034%,测定结果与已知纯度相符。并将测定结果与高效液相色谱(HPLC)法进行了比较。该法具有操作简便,样品用量少,准确度和精密度均较高等优点。     

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%。     

DSC测量中校正对热分析结果的影响

介绍了灵敏度及温度校正对基线和实验结果的影响.仪器温度和灵敏度校正可以减小差示扫描量热法(DSC)曲线的漂移,曲线上得到的温度和焓变值更接近理论值,减小了实验误差.所以,定期对仪器进行重新校正是必要的.     

聚乳酸-聚乙二醇单甲醚共混体系的调制DSC分析

采用调制差示扫描量热法(MDSC)研究了聚乳酸(PLA)与聚乙二醇单甲醚(MPEG)共混体系的热性能。研究结果表明,MDSC可有效分辨PLA重结晶和熔融的重叠效应,在测试条件下,PLA的α’-α晶型转变与α晶体的熔融几乎同时进行。随着升温速率的加快和调制周期的延长,当增塑剂的质量分数为15%时,PLA-MPEG共混物分割在不可逆曲线的重结晶焓逐渐升高(最高约28J/g),熔融焓逐渐降低(最低约为3.3J/g);分割在可逆曲线的熔融峰逐渐由多重峰变为单峰,且焓变值逐渐升高(最高约66.1J/g),相应的可逆曲线熔融分割比例达到了95.2%。通过提高升温速率和延长调制周期,可使大部分熔融分割在可逆曲线上,但过快的升温速率和过长的调制周期会导致PLA相转变时的周期数过少,DSC调制功能的分辨率下降,设置测试条件时需综合考虑。     

多种分析方法测定邻氯代苯亚甲基丙二腈的纯度

采用差示扫描量热单峰法对邻氯代苯亚甲基丙二腈(西埃斯)的纯度进行了测定,通过对升温速率的优化,采用密闭不锈钢耐压池,降低了西埃斯本身挥发性的影响,获得了不同质量样品的纯度值,并与高效液相色谱、气相色谱-质谱和核磁共振等方法的测定结果进行了比较。结果表明:差示扫描量热单峰法、高效液相色谱法、气相色谱质谱法和核磁共振法测定的纯度值分别为99.89%、99.92%、99.25%和95.0％,测定结果最大相差4.92％。 并讨论了不同分析方法产生偏差的原因。     

没食子酸丙酯纯度标准物质的研究

研制了没食子酸丙酯纯度标准物质。依据国家《一级标准物质研制技术规范》,采用高效液相色谱(HPLC)法和差示扫描量热(DSC)法对没食子酸丙酯纯度标准物质进行联合定值,进行了相应的不确定度评定。研制的没食子酸丙酯纯度标准物质定值结果为(99.8±0.5)%(k=2,P=0.95)。该标准物质可用于相关药品生产及使用单位的质量控制和分析方法确认评价。     

Vapour liquid equilibria of monocaprylin plus palmitic acid or methyl stearate at P = (1.20 and 2.50) kPa by using DSC technique

The Differential Scanning Calorimetry (DSC) technique is used for measuring isobaric (vapour + liquid) equilibria for two binary mixtures: {monocaprylin + palmitic acid (system 1) or methyl stearate (system 2)} at two different pressures P = (1.20 and 2.50) kPa. The obtained PTx data are correlated by Wilson, NRTL and UNIQUAC models. The original UNIFAC group contribution method is also considered and new binary interaction parameters for the main groups CH₂, CCOO, OH and COOH are regressed, to account for the non-idealities found in these lipid systems. Established thermodynamic consistency tests are applied and attest the quality of the measured data. In terms of relevance of the selected components, system 1 can be found in the purification and deodorization steps during the production of edible oils, while, system 2 can be found in the purification steps of biodiesel. It should be noted that no such data could be found in the open literature, not only for the specific components selected but also for the combination of the classes of components considered; that is, acylglycerol plus fatty acid or fatty ester.     

Obtaining Modulated Temperature DSC Curves Through a Non-conventional DSC Method

The DSC curve obtained in conventional equipment usually only shows the resultant thermal effect due to simultaneous phenomena, which may occur during isothermal or dynamic analyses. This does not allow one to identify the processes properly and may cause an erroneous interpretation of the resulting curves. Modulated DSC equipment enhances the operating conditions and the analysis capacity of conventional DSC by superimposing a sinusoidal temperature modulation on the linear temperature control. Thus reversing and non-reversing heat flow curves are obtained, which are, respectively, the heat capacity and kinetic components of the DSC curve. Therefore, events that are related to these components can be separately analyzed. A method to obtain curves similar to the MDSC reversing and non-reversing components was developed using conventional DSC equipment in a non-conventional way. It was applied to analyze samples of poly(ethylene terephthalate) (PET) taken from bottles of mineral water. The second PET crystallization step that occurs during its melting was quantified and an apparent initial crystallinity was obtained from the resulting data. This revised version was published online in August 2006 with corrections to the Cover Date.     

甲基苯丙胺标准物质的定值与不确定度分析

为了建立法庭科学毒品检测量值溯源体系,研制了甲基苯丙胺纯度标准物质。通过红外光谱、质谱法对甲基苯丙胺样品进行定性分析,优化并建立了高效液相色谱(HPLC)、差示扫描量热法(DSC)两种定值分析方法。采用热重分析法和电感耦合等离子体质谱法测定水分和无机离子的含量。通过均匀性与稳定性检验结果表明,甲基苯丙胺标准物质的均匀性良好,稳定性至少1年,同时对其进行了不确定度评定。研制的甲基苯丙胺标准物质的纯度为99.8%,扩展不确定度为0.2%(k=2)。     

Thermal analysis applied to the characterization of degradation in soil of polylactide: I. Calorimetric and viscoelastic analyses

An accelerated soil burial test has been performed on a commercial polylactide (PLA) for simulating non-controlled disposal. Degradation in soil promotes physical and chemical changes in polylactide properties, which can be characterized by Thermal Analysis techniques. Physical changes occurred in polylactide due to the degradation in soil were evaluated by correlating their calorimetric and viscoelastic properties. It is highly remarkable that each calorimetric scan offers specific and enlightening information. Degradation in soil affects the polylactide chains reorganization. A multimodal melting behavior is observed for buried PLA, degradation in soil also promotes the enlarging the lamellar thickness distribution of the population with bigger average size. Morphological changes due to degradation in soil lead to an increase in the free volume of the polylactide chains in the amorphous phase that highly affected the bulk properties. Thermal Analysis techniques provide reliable indicators of the degradation stage of polylactide induced by degradation in soil, as corroborated by molecular weight analysis.     

美雄酮甲醇溶液标准物质的定值及不确定度评定

针对目前食品中兴奋剂类药物检测的需求,研制了美雄酮甲醇溶液国家级标准物质.通过对经筛选的市售原料纯品进行液相色谱-质谱和红外光谱定性分析后,研究利用高效液相色谱法(HPLC)和差示扫描量热法(DSC)对美雄酮蛋白同化类固醇类兴奋剂原料进行纯度定值.利用HPLC在245nm监测,以水(含0.1%HAc)+乙腈=50+50...     

苯丙烯酸衍生物的热力学特性研究

激光染料分子——香豆素系列化合物【‘－‘1，8一经甲基香豆素衍生物【‘，’1的相变温度和相变偿分别与其母体7一位、6一位取代基团特性有着相互依赖关系．本文采用DSC法研究了2、3和4一甲氧基苯丙烯酸及个经基一3一甲氧基苯丙烯酸防们分别简称为1、D、m和w）在升温过程中的相变热力学特性，并对它们的结构与其热力学参数之间的关系进行了简要地分析．苯丙烯酸1、H、m和w的结构上。下：1实验部分1．1试样来源合成得到的试样，经鉴定其结构与分子式相符，并经元素分析测定，测定值与理论值相一致，表明试样具有较高纯度．1．2实验方法P…     

水合和pH对蛋白酶K热诱发转变影响的量热法研究

用差示扫描量热法, 在310～450 K温度范围、0.048～4.39克水/克干酶以及pH3～9范围内研究了蛋白酶K(EC 3.4.21.14)的热变性。分别提出表征热变性过程的三个主要热力学参数: 热变性温度T_d、比变性焓△H_d及超额表观比热C_(ex)~(max)和总水量h以及pH的关系。除Td和h的关系属于Flory-Garrett类型外, 蛋白酶K的热变性热力学特征和已报道的球蛋白、双螺旋蛋白及三螺旋蛋白不相同。一级水合水对蛋白酶K热变性热力学特征有最大的影响, pH也是影响该酶热稳定性的重要因素。     

4-甲氟基香豆素衍生物的热力学特性研究

This paper describes the DSC study of 4-trifluorocoumarin derivatives, C_(481), C_(485), C_(500) and C_(480), providing their DSC thermograms and thermodynamic parameters during the phase transitions of these compounds. Singlemelting peaks were observed on DSC thermogram respectively.Experimental results show the existence of certain correlations between the melting point, heat of fusion and molecular structure for this series of compounds.     

Step-scan TMDSC and high rate DSC study of the multiple melting behavior of poly(1,3-propylene terephthalate)

The multiple melting behavior of poly(1,3-propylene terephthalate) (PPT) samples after isothermal crystallization from the melt was studied. The step-scan temperature-modulated differential scanning calorimetry (TMDSC) and high rate DSC were used to investigate this behavior in conjunction with standard DSC, wide-angle X-ray diffraction (WAXD) and polarizing light microscopy (PLM). The effect of PPT average molecular weight on the melting was also examined. In general multiple endotherms after isothermal crystallization of PPT were attributed to a continuous crystal perfection process during the subsequent heating scan via melting-recrystallization-remelting. Multiple melting behavior was more pronounced for the low molecular weight PPT. Step-scan TMDSC showed that extensive recrystallization occurs in PPT samples, especially after rapid isothermal crystallization. In fact two recrystallization exothermic peaks were observed. High rate DSC revealed the initial morphology generated during the isothermal step and showed that the low and middle peaks are associated with melting of primary crystals while the high temperature peak should be attributed to melting of recrystallized material.