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891.
I. perlingová L. Dabrowská J. Kuera M. Tichý 《Fresenius' Journal of Analytical Chemistry》1995,352(1-2):87-91
Two batches of a reference material Creatinine in Human Urine have been prepared with creatinine concentrations at the physiological level, and used in interlaboratory comparisons in which up to 26 laboratories participated employing up to 4 independent methods. The 95% confidence intervals obtained for the certified creatinine concentrations are better than the acceptable ranges of commercially control samples available for clinical laboratories, the certified values being traceable to mean values of the commercial control samples. Thus, a suitable reference material has been prepared for the quality assurance of environmental and occupational health studies in which the concentration of a pollutant or its metabolites in human urine has to be related to the creatinine concentration. 相似文献
892.
In contrast with previous reports, it was found that the reaction of 1-phenylcyclohexene with peroxyformic acid is not entirely stereospecific, but gives some trans-1-phenylcyclohexane-1, 2-diol (IV) beside the cis-isomer (III). The reaction of 1-phenylcyclohexene oxide (II) with formic acid yielded a similar mixture of III and IV, while addition of trichloroacetic acid in benzene was entirely cis-stereospecific. Reaction of the epoxide II with potassium hydroxide took place only under very drastic conditions to give a small yield of III, while sodium 2-dimethylaminoethoxide added exclusively in a trans way, leading to the amino ether X, which was easily transformed into the trans-glycol IV. The latter compound was also the main product of the borohydride reduction of 2-hydroxy-2-phenylcyclohexanone (IX). Possible explanations of the observed stereochemical results are discussed. 相似文献
893.
Summary The method for estimation of iodide formulated in the earlier publications of the series bas been modified by the use of sodium fluoride as the complexing agent in the place of oxalate or phosphoric acid. The results obtained are in excellent agreement with the calculated ones and the method has been successfully applied for the estimation of iodide in iodized salt. 相似文献
894.
Both enantiomers of trans-2,3-diphenylphosphinomethyl-norbornene-(5), prepared by two independent synthetic routes, were used as ligands in the asymmetric hydrogenation of -acetamidocinnamic acid in the presence of rhodium(I). Small variations in the ligand structure have a remarkable influence on the activity of the catalytic system.
-2,3----(5), , - (I). .相似文献
895.
Summary 1. It has been established that the method of precipitation with ethanol in the presence of an increased concentration of Mg2+ can be used for the rapid isolation of the ribosome fraction from plant material.2. The optimum conditions for the complete precipitation of the ribosome fraction from a homogenate of cotton seeds have been selected.3. By treating an extract of the seeds with 0.5 M KCl it was possible to reduce the amount of tRNA in a preparation of the total rRNA.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 852–856, November–December, 1977. 相似文献
896.
Spontaneous vesicle formation was observed in aqueous mixtures of partially hydrolyzed polyacrylamide and single-tailed cationic surfactants. The influences of pH, addition of long-chain alcohols, variation of hydrocarbon chain length, and head group size of the cationic surfactants were investigated systematically. It was found that 30-50% hydrolyzed degree of polyacrylamide and cationic surfactants with 10 or 12 methylene groups are suitable for vesicle formation in the mixed aqueous systems at pH 9.2. Addition of long-chain alcohols was found to be helpful for vesicle formation in some cases. The vesicle stability was also investigated at various temperatures and amounts of ethanol addition. Copyright 2001 Academic Press. 相似文献
897.
Summary Spot tests have been described for calcium sulphate, lead sulphate, silver, thallium and formaldehyde based on the reaction with selenosulphate. In these reactions either red elemental selenium (CaSO4, CH2O) or black metal selenide (PbSO4 Tl, Ag) is formed. The limits of identification are: 0.2 mg of PbS04 or CaSO4, 2 g of Ag, 10 g of Tl, 0.2 g of CH2O.
This paper has been dedicated to Prof. Dr.Fritz Wessely, Vienna, on the occasion of his 70th birthday. 相似文献
Zusammenfassung Für Calciumsulfat, Bleisulfat, Silber, Thallium und Formaldehyd werden Tüpfelproben beschrieben, die auf Umsetzungen mit Selenosulfat beruhen. Hierbei -wird entweder rotes elementares Selen abgeschieden (CaSO4 CH2O) oder schwarze Selenide werden gebildet (PbSO4, Tl, Ag). Die Nachweisgrenzen betragen: 0,2 mg PbSO4 oder CaSO4, 2 g Ag, 10 g Tl, 0,2 g CH2O.
This paper has been dedicated to Prof. Dr.Fritz Wessely, Vienna, on the occasion of his 70th birthday. 相似文献
898.
Summary Thorium and zirconium can be quantitatively precipitated by quinaldinic acid atph 2.7 and 3, respectively. As the precipitates are of nonstoichiometric composition they are to be ignited to oxides. By this reagent thorium can be quantitatively separated from arsenic (As3+), mercury (Hg2+), rare earths, manganese, magnesium and alkaline earths and zirconium from all the aforesaid ions excepting rare earths which contaminate to a slight extent. 相似文献
899.
Summary The previously described gravimetric determinations of silver were used for the potentiometric and amperometric determinations of silver in the presence of interfering cations. The potentiometric titration of silver with MFTD (MBT) is a simple matter, if enough complexone is present, in both ammoniacal and neutral solutions. The amperometric determination of silver with MFTD (MBT) is carried out in neutral solution, containing complexone, with rotated platinum electrode and mercury-mercuric iodide half-cell, short-circuited through a microammeter. The only interfering elements are mercury, gold, and some of the platinum metals. 相似文献
900.
B. I. Popov L. L. Sedova G. N. Kustova L. M. Plyasova Yu. V. Maksimov A. I. Matveev 《Reaction Kinetics and Catalysis Letters》1976,5(1):43-49
In the study of the Fe1–xCrxMo1·5O6 system by X-ray, IR and Mössbauer methods the formation of solid state substitution solutions has been detected, which possess similar catalytic properties in methanol oxidation.
, , Fe1–xMo1·5O6 , .相似文献