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Duolite GT-73 resin was used for the preconcentration of Hg(II) from hydrochloric acid media as well as separation of the analyte from diversity of the co-existing metal ions (Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn) in off-line column operation. Due to the high affinity of the resin to the transition metals, Hg was adsorbed alongside with the foreign metals investigated. A complete release of the concomitant metals from the resin without the desorption of Hg was carried out using solutions of HCl and HNO3. A quantitative recovery of Hg was obtained by digestion of the resin using a H2SO4 and H2O2 mixture in an open-vessel system. An enrichment factor of 40 was achieved. The devised procedure was applied for the determination of Hg(II) in tap-water samples. 相似文献
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4.
Pawel Hitczenko 《Probability Theory and Related Fields》1988,78(2):223-230
Summary It is shown that for all tangent sequences (d
n) and (e
n) of nonnegative or conditionally symmetric random variables and for every function satisfying the growth condition (2x)(x) the following inequality holds:
. This generalizes results of J. Zinn and proves a conjecture of S. Kwapie and W.A. Woyczyski. 相似文献
5.
Blaylock GT Bolton T Brown JS Bunnell KO Burnett TH Cassell RE Coffman D Cook V Coward DH Dorfan DE Dubois GP Eigen G Eisenstein BI Freese T Gladding G Grab C Heusch CA Hitlin DG Izen JM Köpke L Li A Lockman WS Mallik U Matthews CG Mir R Mockett PM Mozley RF Nemati B Odian A Parker J Parrish L Partridge R Pitman D Sadrozinski HF Scarlatella M Schalk TL Schindler RH Seiden A Simopoulos C Stockdale IE Stockhausen W Thaler JJ Toki W Tripsas B Villa F Wasserbaech S Wattenberg A Weinstein AJ 《Physical review letters》1987,58(21):2171-2174
6.
Marek Szymo
ski Jacek Ko
odziej Zbigniew Postawa Pawel Czuba Piotr. Piatkowski 《Progress in Surface Science》1995,48(1-4):83-96
Inelastic interactions of electrons with surfaces of ionic crystals result in emission of various particles such as ions, atoms and molecules. We will review such electron-stimulated desorption processes for the particular class of ionic crystals, namely for alkali halides. In this case, a dominant fraction of the emission is in the form of halogen and alkali atoms characterized by a thermal (Maxwellian) spectrum of translational energies. For several alkali halides (potassium and rubidium chlorides, bromides, and iodides), however, a significant part of the halogen atoms is ejected with nonthermal energies, i.e. energies of the order of 0.1 eV. The results of recent systematic studies of angular-resolved kinetic energy distributions of the emitted particles will be reported and current views on the electronic mechanisms of desorption will be described. In particular, it will be shown that the ESD mechanism can be understood in terms of the model involving a surface localisation of the so called “hot-holes” created by electron bombardment of alkali halides. A role of hot holes in ESD processes will further be discussed in relation to very recent experimental results obtained for the KBr crystals doped with In impurities which act as efficient hole traps. 相似文献
7.
A. Sionkowska M. Wisniewski G.F. Poggi C.A. Maxwell 《Polymer Degradation and Stability》2006,91(12):3026-3032
The thermal and mechanical properties of collagen/chitosan blends before and after UV irradiation have been investigated using thermal analysis and mechanical (Instron) techniques. Comparisons were made with the thermal and mechanical properties of both collagen and chitosan films. Air-dried collagen, chitosan and collagen/chitosan films were exposed to UV irradiation (wavelength 254 nm) for different time intervals. Thermal properties of collagen/chitosan blends depend on the composition of the blend and are not significantly altered by UV irradiation.Mechanical properties such as ultimate tensile strength and ultimate percentage of elongation were much better for collagen films than for collagen/chitosan films. The results have shown that the mechanical properties of the blends were greatly affected by the duration of UV irradiation. Ultimate tensile strength and ultimate percentage elongation decreased after UV irradiation of the blend. Increasing UV irradiation leads to an increase in Young's modulus of the collagen/chitosan blend. 相似文献
8.
The electrolytic sensor described is based on the oxidation of nitrite at a platinum electrode modified with chemisorbed iodine and coated with a thin layer of quaternized poly(4-vinylpyridine), qPVP. The sealed sensor uses an anion-exchange membrane to separate Donnan transport of nitrite across the membrane and controlled potential electrolysis at the Pt/qPVP indicator electrode. The sensor has a linear response to nitrate concentration in aqueous samples over the range 4 × 10?6?2 × 10?3 M nitrite. The detection limit is 2 × 10?6 M nitrite. The sensor is free of interference by nitrate, dissolved oxygen, cations, and many neutral species. Anions that are electroactive at 0.7 V vs. Ag/ AgCl would interfere, but they are uncommon in most samples. Initial tests with lake water samples suggest that this sensor is unaffected by this matrix. The system was also evaluated for monitoring nitrite levels in spiked meat extracts. 相似文献
9.
An analytical derivation of multicenter and multiparticle integrals for explicitly correlated Cartesian Gaussian-type cluster functions is demonstrated. The evaluation method is based on the application of raising operators that transform spherical cluster Gaussian functions into Cartesian Gaussian functions. 相似文献
10.
The effects of substituents at C5, C6 and C7 on the solvolysis rates of 2-norbornyl p-toluene sulfonates confirm that through space induction is directional and depends on distance and bridging strain. 相似文献