流动注射-氢化物发生-原子吸收光谱法测定木糖中痕量砷

食品中砷的测定除国家标准中采用的氢化物发生-原子荧光光谱法外,还有银盐法、砷斑法和还原比色法[1]等,但后3种方法的灵敏度较低,样品处理和操作也较为繁琐,对于痕量砷较难得到准确的结果。氢化物发生-原子荧光光谱法检出限低,需有专用设备;火焰原子吸收光谱法测定[1-2]间接或富集后     

氢化物发生-原子吸收光谱法测定大米中微量砷

砷是一种毒性很大的元素，对人的心肺、呼吸、神经、生殖、造血、免疫系统都有不同程度的损伤作用]。由于大气、地下水、土壤、肥料和农药等污染，砷会在粮食的可食部分积累，因此砷的测定已成为食品和环境监测的必测项目。测砷的常规方法有砷斑法、银盐法。目前，氢化物原子吸收光谱法，氢化物原子荧光法已有报道。本文采用氢化物发生—原子吸收光谱法测定大米中砷，本法具有灵敏度高，干扰少，操作简便等特点，结果满意。     

氢化物发生原子荧光光度法测定水中微量砷

砷是一种对人体有害的元素,在饮用水质量标准中对砷的含量有着严格的要求,建立水中微量砷的快速检测方法有重要意义.氢化物发生原子荧光光度法测定水中微量砷是在酸性条件下,以硼氢化钾为还原剂,使砷与硼氢化钾和酸生成氢化物气体,由载气(氩气)载入石英原子化器,用砷空心阴极灯作激发光源,产生原子荧光,其荧光强度在一定范围内与砷含量成正比.该方法克服了其他分析方法操作繁琐、灵敏度低的缺陷,具有灵敏度高、干扰少、分析速度快的特点.本文探讨应用原子荧光光度计测定水中微量砷的方法.     

氢化物发生原子荧光光谱法测定中药中微量砷

1　引　　言砷是目前公认的对人体有害的微量元素 ,是制定中药质量标准和质量监测中的必测项目。常见的砷的分析方法有原子吸收法、质谱法和分光光度法等。氢化物发生 原子荧光光谱法作为测定砷的国家标准补充方法得到了广泛的应用。该法以其较高的灵敏度、较好的选择性、较小的干扰、较宽的线性范围和较快的分析速度等优点 ,得到了广泛的应用。本文在最佳条件下 ,以 1 2g L碘化钾 +1 0g L硫脲为预还原抗干扰剂 ,建立了断续流动氢化物原子荧光法测定微量砷的方法。2　实验部分2 .1　仪器与试剂　AFS 2 3 0双道原子荧光光度计 (北京海光仪…     

微波消解样品-电感耦合等离子体原子发射光谱法测定食品中总砷

近年来,食品安全已经成为人们关注的热点问题,世界卫生组织将食品安全问题确定为全球公共卫生领域的研究重点。食品中砷及含砷化合物因毒性较大,已被列入必检项目。国家标准GB/T5009.11-2003中测定砷的方法有砷斑法、氢化物原子荧光光谱法、银盐法、硼氢化物还原比色法     

萃取分离-氢化物原子荧光法测定锑精矿中微量砷

在氢化物原子荧光分析中,发现当锑含量高于砷250倍时砷的测定结果明显偏高。另外,大量锑污染仪器管道致使清洗十分困难,从而引起严重的记忆效应。本文采取苯萃取砷(Ⅲ)分离大量锑,然后将砷(Ⅲ)反洗入水相,调节测定液酸度为20％盐酸介质,用氢化物原子荧光法测定砷、该方法避免了大量锑的干扰,同时也解决了锑污染仪器管道等问题。主要仪器和试剂 WYD-2型双道氢化物无色散原子荧光分析仪(江苏宝应无线电厂生产);激发光源:砷无极灯(北京电光源研究所出品);砷标准溶液1μg/mL,20％盐酸介质;碘化钾洗液:2mL 85％KI与98mL HCl(3+1)混合硼氢化钾溶液:1％(微碱性),现用现配。     

氢化物发生-原子荧光光谱法同时测定水中砷和锑

建立在硝酸介质中用氢化物发生-原子荧光光谱法同时测定水中砷和锑的方法。优化了仪器工作条件、酸度、硼氢化钾及还原剂浓度。砷、锑的线性范围为0～10．0μg／L;检出限分别为0．02,0．01μg／L;测定结果的相对标准偏差分别为1．77％～3．72％,2．95％～4．87％（n=6）;加标回收率分别为98％106％,96％105％。该法操作简便,灵敏度高,快速,便于推广,适用于水中砷和锑的同时测定。     

氢化物原子吸收分光光度法测定食品中砷

食品样中砷的测定一般用银盐法,然而此法灵敏低操作繁琐,本法用氢化物原子吸收分光光度法测定食品中的砷则操作简便、快速、灵敏度高.方法灵敏度为0.8ng·ml~(-1),检出限为0.5ng·ml~(-1).1 试验部分1.1 仪器与试剂WYX-402型原子吸收分光光度计HCF氢化物发生器T型石英管砷标准溶液:100ng·ml~(-1)混合酸:硝酸+高氯酸(4+1)盐酸溶液:0.5mol·L~(-1)硼氢化钾:5g·L~(-1)还原剂:称取碘化钾15g、抗坏血酸10g溶解于离子水,定容至100ml.     

氢化物发生—无色散原子荧光法测定人发中微量砷

测定人发中微量砷对医学和环境科学具有重要意义。氢化物发生-无色散原子荧光法具有灵敏度高、干扰少等优点,已报道该法用于土壤、废水及半导体材料中微量砷的测定。本文研究了氢化物发生-无色散原子荧光法测定人发中微量砷的适宜条件。方法快速、简便,样品分析的准确度、精密度良好。     

原子荧光光谱法测定粗锌中的砷

建立了测定粗锌中砷含量的原子荧光光谱法。粗锌样品经硝酸溶液(1+1)低温溶解完全以后,在盐酸介质中,用抗坏血酸预还原,以硫脲掩蔽铜、铁、银等杂质元素,砷被硼氢化钾还原为氢化物,用氩气导入原子化器测量。砷测定结果的相对标准偏差为1.5%~3.0%(n=11),加标回收率为98.4%~103.6%。与国家标准测定方法分光光度法测定结果对比,相对偏差为0.1%~2.4%。该法准确、可靠,适用于砷含量在0.005 0%~0.50%之间的粗锌中砷的测定。     

利用手持技术改进测定乙醇分子结构实验

利用压强传感器代替排水集气法,改进测定乙醇分子结构实验的仪器装置,并探索最佳反应条件。另外,设计两个空白实验,结合压强变化曲线对实验误差进行相关讨论。     

光谱仪测试范围的扩展

由于石化行业的生产需要，其材质的使用具有多样性和广泛性，经常会出现顾客委托的测试样品的一个或几个元素跨越光谱仪现有测试程序测量范围的情况。本法通过对光谱仪测试原理的认识，根据光谱仪的测试能力及标样的采集，实现了一个或几个元素测量范围的扩展，并对其测量的影响因素进行了研究。     

Neutral diterpenoids of oleoresins of five species of conifers of Transcarpathia

The compositions of the neutral diterpenoids of the oleoresins of five species of conifers growing in the Transcarpathia have been studied. It has been found that the oleoresins ofAbies alba M.,Larix decidua M., andPicea excelsa L. contain more than 50% of neutral diterpenoids. The group and qualitative compositions of the oxygen-containing diterpenoids have been determined. In the oleoresins ofAbies alba,Picea excelsa, andPicea abies tertiary alcohols — cis-abienol and isocembrol — predominate, while inLarix decidua the main component is the hydroxy ester larixyl acetate. Primary alcohols related to the resin acids have been found in all the oleoresins investigated. Features of the distribution of diterpenoids according to the species of conifers have been revealed. The results obtained are necessary for the chemotaxonomy of conifers of the family Pinceae.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 812–816, November–December, 1988.     

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.     

Influence of viscosity of medium on processes of oxygen quenching of excited states of mesoporphyrin

The oxygen quenching rate constants for singlet and triplet excited states of the dimethyl ester of mesoporphyrin IX increase with decreasing viscosity of the medium and reach a maximum at a viscosity of approximately 0.4 mPa·sec, after which the rate constants begin to decrease. The drop in rate constant with increasing fluidity of the medium may be related to a nonequilibrium character of the elementary act in the interaction of the reactants in the solvent cage. In viscous media such as isopropyl alcohol, isobutyl alcohol, and isoamyl alcohol, the reaction radius is greater than the sum of the radii of the reacting particles. The long-range character of these processes is due to the relatively weak dependence of the quenching probability on distance.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 161–167, March–April, 1989.     

Determination of heats of detonation and influence of components of composite explosives on heats of detonation of high explosives

The heats of detonation of 20 simple high explosives and explosive mixtures were determined by means of an adiabatic detonation calorimeter designed by the authors. The results indicated that the performance of the instrument was reliable and the experimental data were very accurate. For explosive mixtures, there was a linear accumulative relationship between the heats of detonation of the explosive mixture and its components. Accordingly, the heats of detonation of explosive mixtures could be calculated directly from the heats of detonation of simple explosives and the characteristic heats of other components. The experiments showed that the gold or brass shell of the cylindrical charge could be substituted by a thick-walled porcelain shell, which had the advantage of cheapness.

     

物质分配系数的测定实验改进

实验教学目的是从解决实际问题出发,以实验技术训练和实验设计思想培养为目标。介绍了将单一的物质分配系数测定实验改进为综合实验,提高了实验效果及实验资源利用率。     

Calculation of enthalpies of hydrogenation of hydrocarbons

Sets of hydrogen molecule equivalents have been developed which permit the calculation of hydrogenation of different types of carbon-carbon bonds from ab initio total energies (3-21G and 6-31G* basis sets, and, to a more limited extent, for MP2/6-31G* data) of reactants and products. The calculated enthalpies of hydrogenation are in good agreement with experiment for unstrained molecules, with average errors on the order of 2 kcal/mol. The 6-31G* equivalents allow the enthalpies for strained molecules to be calculated accurately, but the 3-21G equivalents do not. The equivalents for both basis sets have been tested by calculating the enthalpies of hydrogenation of carbon-carbon bonds in nitrogen- and oxygen-containing organic molecules, free radicals, and classical carbocations. The results are in good agreement with experiment in most cases.     

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。