化学计量中不确定度评定研究进展

测量不确定度是表征合理地赋予被测量之值的分散性的参数。本文针对化学计量不确定度评定基础模型仅适用于线性模型、概率分布为正态分布或缩放位移t分布等局限,介绍了近年来不确定度评定的研究热点:蒙特卡罗方法(Monte Carlo Method,MCM),不确定度评定的来源、评定概念、评估方法及其发展过程,扩大了测量不确定度评定与表示的适用范围。     

蒙特卡洛法评定橡胶门尼黏度测量的不确定度

根据高聚物流变学原理,建立了门尼黏度测量模型,分析了模型中各个变量的概率分布,利用Mathcad软件进行了测量模型的门尼黏度模拟,给出了模拟最佳值、不确定度及其包含区间,实现了门尼黏度测量不确定度的蒙特卡洛法评定。与GUM法相比,蒙特卡洛法评定门尼黏度测量不确定度具有编程模式化,过程简单等优点,适合多变量测量模型的不确定度评价。     

MCM法和GUM法评定氨气检测仪示值误差不确定度的对比

氨气检测仪广泛应用于涉氨作业场所,为确保其测量结果准确可靠必须定期对其检定校准。针对其检定过程中示值误差的测量不确定度,对测量不确定度表示指南方法(GUM)和蒙特卡罗法(MCM)进行了对比研究。建立了氨气检测仪示值误差模型,分析了模型中各个变量的概率分布,利用MCM Alchimia软件进行了测量模型模拟计算,给出了模拟最佳值、不确定度及其包含区间,实现了氨气检测仪示值误差测量不确定度的蒙特卡洛法评定。与GUM法相比,蒙特卡洛法评定氨气检测仪示值误差测量不确定度具有通用性强、过程简单、结果可靠等优点,适合氨气检测仪示值误差的不确定度评价。     

电感耦合等离子体质谱法测定岩石中47种元素的不确定度评定

采用封闭酸溶电感耦合等离子体质谱(ICP-MS)法测定岩石样品,分别对47种元素的测量结果不确定度进行评定。通过分析测试方法和测量条件,得到测量结果的不确定度主要由样品称量、样品溶液定容和样品溶液中元素浓度测量引入。在实验室质控条件下,对各不确定度分量进行评定和计算,其中随机因素导致的不确定度采用期间精密度试验综合评价,即采用A类方法评定。共完成了16个岩石国家标准物质(GBW 07103~GBW 07123)47种元素测量结果的不确定度合成,并参照GB/T 6379.2-2004,建立了含量w与扩展不确定度U之间的关系模型,运用这一关系模型可得到测量结果的不确定度估计值,只要测量过程本身或所使用的设备未变化,就不需要再重复进行不确定度评估。     

气相色谱仪检测器的灵敏度和检测限测量结果不确定度的评定

依据JJF1059-1999《测量不确定度评定与表示》评定了气相色谱仪检测器的主要技术指标灵敏度和检测限测量结果的不确定度。分析了各不确定度分量，建立了评定灵敏度、检测限测量结果不确定度的数学模型，并计算了其测量结果的扩展不确定度。     

原子荧光法测定水中砷的不确定度评定

评定原子荧光法测定水中砷的不确定度.结合原子荧光法原理和相关实验流程,根据JJF 1059.1—2012《测量不确定度评定与表示》建立原子荧光法测定水中砷的不确定度测量模型,对整个测定过程中的不确定度来源进行分析.测量不确定度的主要来源包括:取样体积、样品定容体积、由标准曲线上查得砷浓度、样品稀释、重复性测定,分别进行...     

分光光度法测定血清中尿酸的不确定度评定

对分光光度法测定血清中尿酸含量的不确定度进行了评定。根据GUM和QUAM文件规定的不确定度评定指南,确定尿酸测量不确定度的来源主要为重复测定、工作曲线拟合、标准溶液配制、样本和试剂的移取、和反应时间等不确定度分量,其他测量因素引起的分量较小,可以不予考虑。通过合理选择不确定度分量,优化了评定过程,减少了评定环节,达到了对不确定度合理评定的目的。     

液相色谱仪检测器的最小检测浓度测量结果不确定度的评定

依据JJF1059-1999《测量不确定度评定与表示》,评定了液相色谱仪检测器最小检测浓度测量结果的不确定度。分析了各不确定度分量,建立了评定最小检测浓度不确定度的数学模型。检测器最小检测浓度测量结果的相对扩展不确定度为7.1%(k=2.53)。     

非均匀梯度尿液分析仪测量不确定度评定

对非均匀梯度尿液分析仪测量不确定度进行评定。分别采用对称区间不确定度评定方法、选择校准点左右两侧分辨力较大者进行不确定度评定的方法、不对称区间不确定度评定方法对非均匀梯度尿液分析仪测量不确定度进行评定。采用常规的对称区间不确定度评定方法所得出的置信区间左右对称，不符合这类仪器低浓度范围分辨能力高于高浓度范围分辨能力的特性。如果选择校准点左右两侧分辨力较大者进行不确定度评定，虽较为稳妥，但其置信区间宽，不确定度偏大，测量结果准确度偏低。而通过不对称区间不确定度评定方法所得出的置信区间，左侧比右侧窄，且与仪器梯度相符，适合用于非均匀梯度尿液分析仪测量不确定度的评定。     

冷原子吸收分光光度法测定电子电气产品中汞的不确定度评定

根据《测量不确定度评定与表示指南》,对冷原子吸收分光光度法测定电子电气产品中汞含量的测量不确定度进行了评定。分析了影响不确定度的因素,对各不确定度分量进行了计算,结果表明测量不确定度主要来源于标准曲线拟合和测量重复性,合成相对标准不确定度为1.61%。     

非那雄胺合成工艺改进

非那雄胺能抑制5α-还原酶的活性,明显降低二氢睾酮水平,是一种治疗良性前列腺增生的有效药品。该合成工艺以甾烯酮酸为原料,将其与氯化亚砜反应,无须分离即与叔丁胺反应得17β-酰胺化合物,再氧化开环,环合,氢化,脱氢合成了非那雄胺。经元素分析、IR、1HNMR、13CNMR、MS分析表征了其结构。该法无须使用昂贵的2,2-二吡啶二硫化物和剧毒药品苯亚硒酸酐,且以乙酸铵代替氨气,降低了对设备的要求和腐蚀,更适用于工业生产。     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

Acid hydrolysis of carboxymethylcellulose of low degree of substitution

Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position.     

Estimation of Kinetic Parameters of Thermal Oxidation of Ilmenite

The aim of the presented work was the investigation of thermal oxidation of ilmenite in static air atmosphere. The investigations were carried out by use of a derivatograph (MOM, Hungary). The changes of crystallographic structure of investigated samples were identified by X-ray diffractometry on Philips PW-1710 diffractometer. In temperature above 500°C appears structure of hematite Fe₂O₃. On the basis of the thermogravimetric measurements, the contracting area and contracting volume models were found as the best fitting experimental data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mechanism of action of base-catalyzed oxygenation of phenol derivatives

Cyclopropyl derivative of 2,6-di-tert-butylphenol is synthesized as a probe to investigate the mechanism of base-catalyzed autooxidation of phenol derivatives. Our study indicates that one electron reduction of molecular oxygen from phenolate gives phenoxyl radical 3, a key intermediate of autooxidation. The coupling of phenoxyl radical and superoxide radical gives peroxylate anion 4 and produces the final epoxy alcohol adduct 6.     

氯氧化镁生成热的研究

用氧化镁氯化镁水溶液制备了8水合氯氧化镁[nMg(OH)2·MgCl2·8H2O], 并测定了其在盐酸中的溶解热, 实验结果表明, 氯氧化镁溶解热与n值呈线性关系, 根据溶解热求出5Mg(OH)2·MgCl2·8H2O和3Mg(OH)2·MgCl2·8H2O的生成热分别为-7727.1和5888.1kJ·mol^1^-。     

微量钙的测定方法研究进展

介绍了1995-2006年期间测定微量和痕量钙的方法,如电感耦合等离子体-原子发射光谱法、原子吸收光谱法以及离子色谱法等的工作原理和特点,并说明了其测定微量钙的应用领域。并对微量钙的测定技术进行了展望(引用文献55篇)。     

Stages of thermal decomposition of sodium oxo-salts of sulphur

Thermal behaviour of sodium oxo-salts of sulphur: Na₂SO₄, Na₂S₂O₇, Na₂S₂O₆, Na₂SO₃, Na₂S₂O₅, Na₂S₂O₄, Na₂S₂O₃, Na₂S₃O₆ and of sulphides Na₂S and Na₂S₂ was studied on heating up to 1000°C. The experiments were performed with anhydrous compounds obtained from commercial products by recrystallisation and dehydration. The stage mechanisms of decomposition of anionic sub-lattices of the salts have been proposed basing on the Górski’s morphological classification of simple species. The thermal stability and the stage decomposition mechanisms were correlated with the structure and the potential chemical properties of the salt anions. The thermal decomposition processes were studied by means of thermal analysis, and the decomposition products were identified by means of X-ray phase analysis.     

Synthesis of phenolic components of Grains of Paradise

Two vanilloids, (5E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one (1) and 4-[3-hydroxydecyl]-2-methoxyphenol (2), isolated from the dried seeds of Grains of Paradise (Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared.