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971.
Partha?ChattopadhyayEmail author Andrew S.?Fisher Derek N.?Henon Steve J.?Hill 《Mikrochimica acta》2004,144(4):277-283
An environmentally friendly and simple method has been developed for complete digestion of lead, cadmium and antimony from soil samples using a magnesium nitrate assisted dry ashing procedure. Statistical data for a series of experiments with standard reference materials are presented, and precision values are found to be comparable for inductively coupled plasma-mass spectrometry and for inductively coupled plasma-atomic emission spectrometry. From a single digest solution all analytes are quantified without involving any pre-concentration routes. Inter-method comparison of inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) shows that the probability of the results being different is less than 99%. 相似文献
972.
The choice of an analytical procedure and the determination of an appropriate sampling strategy are here treated as a decision theory problem in which sampling and analytical costs are balanced against possible end-user losses due to measurement error. Measurement error is taken here to include both sampling and analytical variances, but systematic errors are not considered. The theory is developed in detail for the case exemplified by a simple accept or reject decision following an analytical measurement on a batch of material, and useful approximate formulae are given for this case. Two worked examples are given, one involving a batch production process and the other a land reclamation site. 相似文献
973.
Cristina Tealdi M. Saiful Islam Craig A.J. Fisher Lorenzo Malavasi Giorgio Flor 《Progress in Solid State Chemistry》2007,35(2-4):491-499
The NdCoO3 perovskite has been investigated using a combination of atomistic simulation and experimental techniques to examine its possible use as an oxidation catalyst and/or sensor material. The sensing properties of NdCoO3 and Nd0.8Sr0.2CoO3 towards CO have been investigated by employing thin films deposited by means of radio-frequency (RF) magnetron sputtering onto polycrystalline Al2O3. The response of the films was monitored by performing four-probe DC-conductivity measurements. The conductivity variation induced by switching between a CO-free atmosphere (air) and a CO-rich one with the same composition of residual gas was recorded and analysed as a function of temperature; results are compared for the two samples. Simulation studies focussed on the dopant, transport and redox properties of the pure material; the results indicate that Sr and Ca on the Nd site are the most soluble dopants and that when divalent dopants are incorporated in the structure, charge compensation occurs via oxygen ion vacancies. The low activation energy for oxygen vacancy migration suggests high oxide-ion mobility through the lattice. Particular attention is paid to the electronic processes because of their importance with respect to practical applications of the material. 相似文献
974.
Michael addition of ethyl malonate, alkylmalonate and phenylacetate to 2-methylene-quinuclidin-3-one, followed by NaBH4 reduction of the 3-oxo group in the resulting adduct, then acid hydrolysis and decarboxylation (in the case of malonates) gave 6-oxa-1-azatricyclo-(4.2.2.02,7)dodecan-5-one, its 4-alkyl and 4-aryl derivatives. A minor byproduct is 2-(trans-3-hydroxyquinuclidin-2-yl)-α-alkyl-propanoic acid which is unable to undergo cyclization to δ-lactone. 相似文献
975.
Electrical-conductance measurements have been made at 25° C up to concentrations of 0.06M in aqueous solutions of Na2SO4 at atmospheric pressure and as a function of pressure up to 2000 atm. Calculations of the change of the dissociation constant for the NaSO 4 ? ion pair with pressure indicate that the difference in partial molal volumes between products and reactants at infinite dilution is \(\Delta \bar V^ \circ \tilde = - 8.25{\text{ }}cm^3 /mole\) . Using the equation of Davies, Otter, and Prue, we found the average dissociation constants for five concentrations between 0.005 and 0.06 moles/liter to be 0.097, 0.131, and 0.165 at 1, 1000, and 2000 atm, respectively, with a standard deviation of ±0.003. The atmospheric-pressure value is 0.080±0.016 over the entire concentration range from 0.00005 to 0.06 moles/liter, about half that obtained by Jenkins and Monk. This is consistent with a value ofK=0.077±0.006 recalculated from the limited-concentration-conductance work of Jenkins and Monk, with a value ofK=0.073 obtained by Fisher from data of Kurtze and Tamm on ultrasonic absorption in MgSO4?NaCl solutions, and withK=0.067 calculated by Fisher from the potentiometric data of Pytkowicz and Kester at high ionic strength. The relationship of this work to sound absorption and ion pairing in seawater is discussed. The predicted pressure dependence of the NaSO 4 ? ion pair in seawater from this work differs substantially from earlier work by Kester and Pytkowicz and by Millero. 相似文献
976.
Ahmed Abdullah Fazlul Huq Ashraf Chowdhury Hasan Tayyem Philip Beale Keith Fisher 《BMC chemical biology》2006,6(1):3-9
Background
Cis-planaramineplatinum(II) complexes like their trans isomers are often found to be active against cancer cell lines. The present study deals with the synthesis, characterization and determination of activity of new cis-planaramineplatinum(II) complexes. 相似文献977.
Neumann D Fisher M Tran L Matisons JG 《Journal of the American Chemical Society》2002,124(47):13998-13999
Organic-inorganic hybrids are an important class of new materials that offer improved thermal and mechanical properties over normal polymers. They may be produced by either the sol-gel route or through the use of inorganic compounds possessing reactive functional groups. Polyhedral oligosilsesquioxanes (POSS) are completely defined molecules of nanoscale dimensions that may be functionalized with reactive groups suitable for the synthesis of new organic-inorganic hybrids. Here we report the synthesis and characterization of a novel POSS possessing eight isocyanate groups via the hydrosilylation of octakis(hydridodimethylsiloxy)octasilsesquioxane (Q8M8H) and m-isopropenyl-alpha,alpha'-dimethylbenzyl isocyanate (m-TMI). The suitability of this new macromer to the synthesis of a organic-hybrids has been explored by forming a new type of highly cross-linked polyurethane elastomer via reaction of the macromer with poly(ethylene glycol) using dibutyltin dilaurate catalyst. 相似文献
978.
Robert J. De Vita Alison J. Frontier William R. Schoen Matthew J. Wyvratt Michael H. Fisher Kang Cheng Wanda W.-S. Chan Bridget S. Butler Roy G. Smith 《Helvetica chimica acta》1997,80(4):1244-1259
The synthesis of a variety of potent macrocyclic growth hormone secretagogues, i.e. 5 , 9 , 12 , and 20 – 22 , based on the known lead structure L-692,429 ( 1 ) is described. These conformationally constrained growth hormone secretagogues were prepared by joining the two essential pharmacophores, the amino-acid side chain at the 1H-1-benzazepine moiety and the 1,1′-biphenyl moiety with a variety of linkers. The most potent analog was found to be L-744,080 ( 21 ), a derivative in which a 2′-carboxamide moiety at 1,1-biphenyl is N,O-joined to the OH group of the (2-hydroxypropyl)amino-acid side chain by a C4 ester linker. This potent analog may be useful in determining the bound conformation of the benzolactam class of growth hormone secretagogues at the newly identified GHS receptor, L-744,080 ( 21 ) with an ED50 of 20 nM was up to fifty times more potent than the seco-acid precursor and 3-fold more potent than the parent 2′-tetrazole compound L-692, 429 ( 1 ). 相似文献
979.
980.
The application of gas chromatography chemical ionization mass spectrometry to the determination of a variety of alkyl alkylphosphonates, phosphonofluoridates, phosphonothiolates and an amidophosphorocyanidate is described. Comparison is made between the electron ionization and chemical ionization mass spectrometry of these compounds. Chemical ionization mass spectrometry is shown to enhance the capability for identification, especially when a limited sample is available. Results indicate that methane is highly useful for obtaining protonated molecular ions and association ions (formed by the transfer of a reactant ion to a sample molecule) as well as meaningful fragment ions. Ionizing ethylene and isobutane gives protonated molecular ions as base peaks for all of the compounds studied, including those where a lower abundance of the [MH]+ ion is found via methane chemical ionization mass spectrometry. Ethylene is superior to isobutane on the basis of its effectiveness for serving as both a carrier and a reagent gas and gives better sensitivity. Although not an intrinsic part of this present study, analytical sensitivities in the subnanogram range were found. 相似文献