排序方式: 共有25条查询结果,搜索用时 15 毫秒
1.
Dula Amarasiriwardena Steven F. Durrant Alexandra Lásztity Antoaneta Kvska Mark D. Argentine Ramon M. Barnes 《Microchemical Journal》1997,56(3):352-372
Semiquantitative analysis with accuracy of ±30 to 50% is a valuable tool for rapid screening of samples prior to quantitative determination of trace metals. In this study semiquantitative analysis software available with commercial inductively coupled plasma–mass spectrometry (ICP-MS) instrumentation is applied for rapid multielemental analysis, and the accuracy and precision of this semiquantitative analysis approach is evaluated with biological certified reference materials. Samples were prepared by high-pressure, high-temperature nitric acid vapor-phase digestion. For most elements the measured semiquantitative results are in the range of the certified values. With appropriate analyte solution dilution, the measured concentrations of the major elements (e.g., Ca) also agree with certified values. The accuracy is within ±10% for 28 element determinations that include 16 individual elements (Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Rb, Sb, Sr, Tl, and Zn) and ±20% for 54 element determinations that include three more elements (Mg, V, and U) in eight certified reference materials including water. The method precision is 11 ± 11% (relative standard deviation,n= 65). 相似文献
2.
Theodora Zapryanova Antoaneta Hrussanova Alexander Milchev 《Journal of Electroanalytical Chemistry》2007,600(2):311-317
The nucleation and growth of copper crystals on a glassy carbon electrode are investigated at different constant overpotentials. Current transients are recorded and the number of copper nuclei is microscopically registered. The experimental data for the growth current are interpreted according to the theories of progressive and instantaneous nucleation and information is obtained on the stationary nucleation rate, the saturation nucleus number density and the exchange current density at the crystals–solution interface boundary. 相似文献
3.
A simple method to produce silver nanoparticles on a glass surface from silver nanolayer deposited by magnetron sputtering and thermal annealed is presented. Localized surface plasmon resonance of nanoparticles shows a red shift depending on the silver nanolayer thickness, the refractive index and the thickness of an ultra-thin silicon compound adsorbed on the surface. A highly enhanced Raman spectrum of the characteristic groups of a silicon compound adsorbed on the nanoparticles surface was obtained. 相似文献
4.
Antoaneta Krushevska Mihály Kotrebai Alexandra Lásztity R. M. Barnes Dulasiri Amarasiriwardena 《Fresenius' Journal of Analytical Chemistry》1996,355(7-8):793-800
Water soluble tertiary amines enhance signals and decrease polyatomic chloride interferences in the direct inductively coupled plasma – mass spectrometric (ICP-MS) determination of As and Se in biological samples. Preliminary experiments with amine concentrations and nebulizer flow rates produced element and interference signal intensity changes. Arsenic and Se ICP-MS determination parameters have been optimized by a simplex procedure with amines in an argon plasma or without amines but with addition of N2 to the Ar. Variables include RF (radio frequency) power, nebulizer gas flow rate, intermediate gas flow rate, and amine concentration or nitrogen gas flow rate. Detection limit, minimization of polyatomic ion intensities, and reproducibility have been evaluated as reponse factors. The signal enhancement and element-to-molecular interference ratios differ to some extent with analyte intensity optimum operating conditions. The detection limits with addition of nitrogen (16 pg mL–1 for As and 180 pg mL–1 for Se) or of amines (8 pg mL–1 for As and 120 pg mL–1 for Se) and the extent of chloride interference minimization were compared. Amines addition was more beneficial. Biological standard reference materials and food and fecal samples were analyzed following different sample dissolution procedures. 相似文献
5.
Prof. Dr. Antoaneta D. Stefanova Philip I. Iotov Dimcho I. Dimitrov 《Monatshefte für Chemie / Chemical Monthly》1975,106(3):723-728
The liquid phase oxidation of 1.2.4.5-tetramethylbenzene catalysed by cobaltous acetate and promoted by KBr in acetic acid was kinetically studied. In view of deriving the kinetic equation for the absorption of oxygen, a number of experiments were carried out. The values of the activation energy and of the preexponentA=1014 were determined as well. The resulting kinetic equation: $$ - \frac{{d\left[ {O_2 } \right]}}{{d\tau }} = 10^{14} \cdot \exp \left( { - \frac{{84,460 \times 10^3 }}{{RT}}} \right) \cdot C_{C_6 H_2 (CH_3 )_4 }^{0,5} \cdot C_{Co(OAc)_2 }^{0,5} \cdot C_{KBr}^{0,5} $$ is in accordance with the theoretically derived expression of this type. 相似文献
6.
Antoaneta Delijska und Christina Prveva 《Fresenius' Journal of Analytical Chemistry》1976,281(4):281-284
Zusammenfassung Eine direkte spektrographische Methode zur Bestimmung von As, Te, Sb, Pb, Sn, Bi, Cd, Ag, W, Ti, Fe, Cu und Zn in Mo(VI)-oxid durch Anwendung eines neuen thermochemischen Reagenses — Tetraäthylammoniumjodid (TEAI) — wurde entwickelt. Der TEAI-Puffer gewährleistet eine vollständigere Trennung der zu bestimmenden Elemente von der Matrix und eine höhere Empfindlichkeit im Vergleich zum bisher verwendeten Graphitpulver. Durch Anwendung eines inhomogenen Magnetfeldes bzw. durch Zufuhr von KJ oder ZnO wird eine weitere nachträgliche Erhöhung der Empfindlichkeit bei der Bestimmung der meisten Verunreinigungen erzielt. Das Verfahren zeichnet sich durch gute Reproduzierbarkeit und Genauigkeit aus.
Direct spectrographic determination of impurities in Mo(VI) oxide using a tetraethylammonium iodide buffer
A direct spectrographic method for the determination of As, Te, Sb, Pb, Sn, Bi, Cd, Ag, W, Ti, Fe, Cu and Zn in Mo(VI) oxide has been developed by using a new thermochemical agent, tetraethylammonium iodide (TEAI). The TEAI-Buffer ensures a complete separation of the elements to be determined from the matrix and a higher sensitivity by comparison with the graphite powder commonly used in practice. A higher sensitivity for most impurities has further been achieved by using an inhomogeneous magnetic field or by adding KI or ZnO, respectively. Main advantage of the method is its good reproducibility and precision.相似文献
7.
Antoaneta Krushevska Mihály Kotrebai Alexandra Lásztity R. M. Barnes Dulasiri Amarasiriwardena 《Analytical and bioanalytical chemistry》1996,355(7-8):793-800
Water soluble tertiary amines enhance signals and decrease polyatomic chloride interferences in the direct inductively coupled plasma – mass spectrometric (ICP-MS) determination of As and Se in biological samples. Preliminary experiments with amine concentrations and nebulizer flow rates produced element and interference signal intensity changes. Arsenic and Se ICP-MS determination parameters have been optimized by a simplex procedure with amines in an argon plasma or without amines but with addition of N2 to the Ar. Variables include RF (radio frequency) power, nebulizer gas flow rate, intermediate gas flow rate, and amine concentration or nitrogen gas flow rate. Detection limit, minimization of polyatomic ion intensities, and reproducibility have been evaluated as reponse factors. The signal enhancement and element-to-molecular interference ratios differ to some extent with analyte intensity optimum operating conditions. The detection limits with addition of nitrogen (16 pg mL–1 for As and 180 pg mL–1 for Se) or of amines (8 pg mL–1 for As and 120 pg mL–1 for Se) and the extent of chloride interference minimization were compared. Amines addition was more beneficial. Biological standard reference materials and food and fecal samples were analyzed following different sample dissolution procedures. 相似文献
8.
Ivanka Kostova Antoaneta Ivanova Bozhanka Mikhova Antonina Vitkova 《Monatshefte für Chemie / Chemical Monthly》2000,131(2):191-194
Summary. A new lignan of the dibenzylbutyrolactone type, haplotonin, was isolated from the aerial parts of Haplophyllum suaveolens together with five known compounds-the alkaloids flindersine, 6-methoxyflindersine, N-acetoxymethylflindersine, and evoxine
and the lignan 4-acetyldiphyllin. This is the first report on the occurrence of N-acetoxymethylflindersine in the genus Haplophyllum and on 6-methoxyflindersine and 4-acetyldiphyllin as constituents of the investigated species.
Received August 10, 1999. Accepted (revised) October 12, 1999 相似文献
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(1) Background: Myoinositol (MI) and D-chiro-inositol (DCI) are involved in a number of biochemical pathways within oocytes having a role in oocyte maturation, fertilization, implantation, and post-implantation development. Both inositols have a role in insulin signaling and hormonal synthesis in the ovaries. (2) Methods: Literature search (with key words: inositols, myo-inositol, d-chiro-inositol, PCOS) was done in PubMed until Sept. 2020 and 197 articles were identified, of which 47 were of clinical trials (35 randomized controlled trials). (3) Results: Many studies have demonstrated that in patients with polycystic ovarian syndrome (PCOS) MI treatment improved ovarian function and fertility, decreased the severity of hyperandrogenism including acne and hirsutism, positively affected metabolic aspects, and modulated various hormonal parameters deeply involved in the reproductive axis function and ovulation. Thus treating with MI has become a novel method to ameliorate PCOS symptoms, improve spontaneous ovulation, or induce ovulation. The current review is focused on the effects of MI and DCI alone or in combination with other agents on the pathological features of PCOS with focus on insulin resistance and adverse metabolic outcomes. (4) Conclusions: The available clinical data suggest that MI, DCI, and their combination in physiological ratio 40:1 with or without other compound could be beneficial for improving metabolic, hormonal, and reproductive aspects of PCOS. 相似文献