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981.
Standardising quality of measurements at both the national and international level results in a unity in measurement that
may be regarded a synonym of traceability. In gas analysis, the key issue in achieving this aim is production of gaseous reference
materials. Establishing a network of secondary measurement standards at gaseous CRM producers’ sites in Ukraine might be interesting
for those involved in gas analysis activities. Inevitably, problems concerning the recognition of measuring capabilities of
both national metrological institutes and local CRM producers are now an international issue. Thus, the problems of national
adoption of international standards, as well as harmonisation between different international documents are currently relevant,
and Ukrainian experience may be useful to others in this field.
Presented at the 3rd International Conference on Metrology, November 2006, Tel Aviv, Israel. 相似文献
982.
983.
984.
R. A. Alieva S. Z. Gamidov F. M. Chyragov A. A Azizov 《Journal of Analytical Chemistry》2005,60(12):1114-1117
A method is developed for cadmium and zinc preconcentration on a minicolumn packed with a new chelating polymer sorbent. The effects of the test solution pH and volume, the sample matrix composition, the eluent volume, and the sample and eluent flow rates are studied. Zinc and cadmium in the eluate are determined by flame atomic absorption spectrometry. Under optimal conditions, the determined ion recovery is more than 95%. The detection limits (3σ, n = 20) are found to be 15.0 (Cd) and 17.2 (Zn) ng/mL. The developed method is employed for cadmium and zinc determination in samples of seawater and water obtained after oil pumping. 相似文献
985.
An amperometric detector with a small thin mercury film electrode is described. The device demonstrates advantageous operational
characteristics such as small dispersion (D<2) and “memory effect” (me<0.6%), extensive maximum sample frequency (msf −200
samples/h), and high sensitivity. It has been proven useful in flow-injection analysis at a constant potential under hydrodynamic
conditions. 相似文献
986.
In the course of investigations on equestrian supplemental products for the presence of doping substances, two products were found to contain forbidden substances. As reported earlier a plant extract (Mexican cactus extract) named “Energy 5” contained the anabolic androgenic steroids (AAS) stanozolol, 17β-hydroxy-17α-methyl-5α-androstane-3β-ol (3β,5α-THMT) as well as mestanolone not declared on the label. In the present study, a product called “Super Kalm Paste” was tested. Analysis by gas chromatography - mass spectrometry (GC-MS) revealed that the preparation contained the class I anti-arrhythmics quinine (trade names KinidinTM, Durules) and cinchonine. The samples were prepared according to a sample preparation procedure established for anabolic steroids in nutritional supplements for humans. The sample treatment comprised the extraction and purification of the analytes as well as the chemical conversion with N-methyl-N-trimethylsilyl-trifluoracetamide (MSTFA) to yield the trimethylsilyl (TMS)-derivatives. To verify whether the administration of such products could lead to positive doping tests, a pilot excretion study on “Energy 5” was conducted with two geldings, and urine samples were collected. Gas chromatography - high resolution mass spectrometry (GC-HRMS) after solid phase extraction and mixed derivatisation has demonstrated the presence of the stanozolol metabolite 16β-hydroxy-stanozolol in urine samples after “Energy 5” application. 相似文献
987.
988.
Heng-Dao Quan Hui-E Yang Masanori Tamura Akira Sekiya 《Journal of fluorine chemistry》2007,128(3):190-195
In this report, a simple process for preparing HFC-245fa through the reaction of 1,1,1,3,3-pentachloropropane (PCP) and anhydrous HF via two-step vapor-phase catalytic fluorination is described. The antimony pentafluoride catalyst was supported on inert porous materials to improve the catalytic activity. The resulting process catalyst not only exhibited high catalytic activity and excellent thermo-stability, but also improved the performance of SbF5, in terms of hygroscopicity and corrosion. 相似文献
989.
本文研究了在表面活性剂存在性,铝与溴代二甲氨基苯基荧光酮的显色反应。在弱酸性介质中,Al^3+BDMAF-CTMAB三元配合物在水浴加热至70℃-80℃时形成,其最大吸收波长为577nm,Al^3+:BDMAF=1:2,表观摩尔吸光系数为1.34×10^5L.mol^-1.cm^-1,表观稳定常数为7.4×10^5。在PH9.5-10.5的氨性缓冲介质中,Al^3+-F^--BDMAF-非离子表面 相似文献
990.
本文利用流化床反应器研究了多元复合氧化物PMo_(12)Bi_3Fe_(8-x)Ce_xK_(0.1)O_y(x=0-8)中稀土元素铈对丙烯氨氧化的催化作用,并用x-射线衍射、红外光谱、扫描电镜和热重技术表征了催化剂的结构,发现x=2-3时,丙烯腈的收率最高。催化剂中存在Fe_2(MoO_4)_3,Ce_2(MoO_4)_3、α-Bi_2O_3、3MoO_3。这三种物相的互相溶解和凝结形成固溶体和准均相,使活源。份在各物相表面或界面上均匀分布,由此产生的各活性组份的协调作用是催化活性的主要来性组铈能抑制MoO_3升华,稳定活性相结构。 相似文献