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排序方式: 共有308条查询结果,搜索用时 15 毫秒
11.
Alejandro Marcó Ramón Compañó Roser Rubio Pilar Domènech Albert Palangues Miguel Maestro 《Mikrochimica acta》2002,140(1-2):131-139
Four inter-comparison exercises on organic elemental analysis were carried out between 1997 and 2001 by the Department of
Analytical Chemistry of the University of Barcelona, together with the Microanalysis Service and the Institute of the Marine
Sciences, which both belong to the CSIC in Barcelona, and the University of A Coru?a. More than sixty laboratories participated
in these exercises. Here we describe the design and characteristics of the trials, the samples and the homogeneity tests applied.
We report the results obtained for the analysis of carbon, hydrogen, nitrogen, sulphur and oxygen, their statistical analysis,
and the most relevant aspects of the technical discussion meetings.
Received December 20, 2001; accepted March 18, 2002; published online July 22, 2002 相似文献
12.
本文采用不同的溶剂对溶解前后的胆色素类结石进行了主要元素的控制,同时对特征色素类结石进行了有机元素分析,通过比较溶解前后超微结构和各种元素含量的变化,认为胆红素与金属离子,尤其是钙及其后二阶金属离子,形成了胆色素盐或配位络合物,并与糖蛋白等螯合成了大分子复合物。这是胆色素类结石难溶的主要原因。 相似文献
13.
相转移催化元素硫的歧化反应 总被引:1,自引:0,他引:1
本工作将相转移催化(PTC)应用于元素硫歧化反应,大大降低了反应温度,提高了反应速度。该反应被证实与熔态硫在水溶液中的歧化相同,即4S+6OH~-=2S~(2-)+S_2O_3~(2-)+3H_2O。比较了四乙基铵、四丁基铵、十六烷基三甲基铵和三辛基甲基铵四种相转移催化剂及四氯乙烯、二甲苯和四氯乙烷三种溶剂的影响。讨论了本体系相转移催化的证据。为改进以元素硫歧化反应为基础的提取冶金过程提供了依据。 相似文献
14.
The current status of plasma source-mass spectrometry (PS-MS) is reviewed. An overview of interference effects that exist, alternative plasma sources available, and mass spectrometer interface studies is provided. A discussion of current and future development areas in plasma source mass spectrometry is also included. 相似文献
15.
ELECTROCHEMICAL POLYMERIZATION OF ANILINE IN PHOSPHORIC ACID AND THE PROPERTIES OF POLYANILINE 总被引:1,自引:0,他引:1
The behavior of the electrochemical polymerization of aniline in a weak acid, phosphoric acid, is very similar to that in strong acids, i.e. its polymerization rate increases quickly with the electrolysis time. The FTIR spectra of polyaniline samples synthesized in phosphoric acid indicate that the counter ion H2PO4^- is present in both the oxidized form and the reduced form of polyaniline. The counter ion plays an important role in adjusting the pH value at the electrode surface of polyaniline during the oxidation and reduction processes. As a result, a pair of redox peaks still appear in cyclic voltammograms of polyaniline in a solution of sodium sulfate of pH 5.5 and in a solution of NaH2PO4 of pH 7.0,respectively, at low potential scan rate; and the color of polyaniline film also changes with applied potential at pH 7.0. Thus,the pH region for the electrochemical activity and the electrochromism of polyaniline is extended to pH 5.5 for a solution of sodium sulfate and to pH 7.0 for a solution of NaH2PO4. The conductivity of polyaniline is 3.3 S cm^-1, depending on the concentration of phosphoric acid used in the stage of polymerization of aniline. The result of elemental analysis of polyaniline is presented here. 相似文献
16.
Robert S. Pomeroy Jeffrey D. Kolczynski Jonathan V. Sweedler M. Bonner Denton 《Mikrochimica acta》1989,99(3-6):347-353
A unique simultaneous emission spectrograph is utilized to perform qualitative and quantitative analysis on trace quantities of solid particulates. The atomic emission spectroscopic system consists of a direct current plasma source and an echelle spectrograph with a charge injection device detector, enabling the system to simultaneously measure the wavelength range from 220 nm to 520 nm with 0.02 nm resolution at 300 nm. Monitoring all wavelengths simultaneously allows the qualitative and quantitative determination of most major and minor constituent in a trace quantity of sample with little prior knowledge about the sample. The ability to perform qualitative and quantitative analysis on particulates is demonstrated by evaluating NBS certified coal fly ash, as well as a sample taken from the respirator air filter at an acute care unit in a hospital.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria 相似文献
17.
镇元素簇合物是人们最感兴趣的簇合物之一l‘-’].已有的。作主要是研究它的稳定性和电子结构,对其成键性质还研究得不多·为止匕我们对Lkin为元素簇合物中所含原子个数,e为该化合物的电荷)进行了定域化研究,并得出一些有意义的结果·1计算我4rl采用GAMESS90程序m,在4-31G基组下进行了正则分子轨道SCFi十算(闭壳层采用RHF,开壳层采用UHF).然后,以QSU90程序问,用B0yS方法进行了定域化计算,得到定域分子轨道(LM),再根据LMO的系数和集居数分析,判断各分子中原子的成键情况问.共计算了18个簇合物.它们的原子数… 相似文献
18.
The use of inductively coupled plasma mass spectrometry (ICP-MS) coupled with separation techniques for the purpose of elemental speciation has recently gained a lot of attention. Much of this is due to ever improving separation capabilities of Chromatographic techniques, the high sensitivity of ICP-MS, and the continuing development of better interface techniques. Additionally, there is a growing awareness of the need to monitor various species of an analyte, rather than just total analyte concentrations, due to their often varying natures. For the sake of learning from different elemental speciation approaches, this review brings together some selected types of elemental speciation which have been recently seen in literature. These include separations using various forms of liquid chromatography, such as reversed phase, reversed phase ion pairing, micelle, ion exchange, and size exclusion. Elemental speciation employing gas Chromatographie separations and supercritical fluid separations are discussed as well as elemental speciation using capillary electrophoresis. 相似文献
19.
20.
Leandro Augusto Gouvêa De Godoi Carla Eloísa Diniz Dos Santos Eugenio Foresti Marcelo Zaiat Márcia Helena Rissato Zamariolli Damianovic 《International journal of environmental analytical chemistry》2019,99(9):809-823
Recent developments in wastewater treatment have led to a renewed interest to obtain elemental sulphur (S°) as a by-product from bioreactors. However, practical studies are limited by the gap of adequate analytical techniques for its determination. This paper provides a statistical study and matrix effect evaluation of an adapted spectrophotometric method for routine S° analyses in aqueous samples, based on a methodology previously described by Hart (1961). Four complex matrices were tested: domestic sewage and effluent samples from three different bioreactors. Tested performance criteria included linearity, matrix effect, limit of detection and quantification and S° recovery. Results were linear (R2 = 0.99994) in the studied range (5 to 100 mg S° L?1) and no matrix effect was observed. The accuracy was based on recovery values that varied from 100% to 106%. The colloidal S° separation and extraction protocol was also considered suitable for aqueous samples, reaching more than 99.0% of S° recovery. 相似文献