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81.
James Murphy Phil Jones Steve J. Hill 《Spectrochimica Acta Part B: Atomic Spectroscopy》1996,51(14):1867-1873
A simple and accurate method has been developed for the determination of total mercury in environmental and biological samples. The method utilises an off-line microwave digestion stage followed by analysis using a flow injection system with detection by cold vapour atomic absorption spectrometry.
The method has been validated using two certified reference materials (DORM-1 dogfish and MESS-2 estuarine sediment) and the results agreed well with the certified values. A detection limit of 0.2 ng g−1 Hg was obtained and no significant interference was observed. The method was finally applied to the determination of mercury in river sediments and canned tuna fish, and gave results in the range 0.1–3.0 mg kg−1. 相似文献
82.
83.
M. G. Ezernitskaya B. V. Lokshin T. Yu. Orlova V. N. Setkina V. I. Shilnikov S. Nunziante Cesaro 《Russian Chemical Bulletin》1994,43(11):1841-1845
FTIR spectra have been studied for staircase cyclopentadienyl complexes containing two or three metal carbonyl fragments bound by the metal-carbon bond Cp(CO)2Fe-CpmMn(CO)3 (1), Cp(CO)2Fe-CpmFe(CO)2CH2Ph (2), Cp(CO)2Fe-Cpm(CO)2Fe-CpmMn(CO)3 (3), Cp(CO)2Mo-Cpm(CO)2Fe-CpmMn(CO)3 (4), Cp(CO)3W-Cpm(CO)2Fe-CpmMn(CO)3 (5), Cp(CO)2Fe-Cpm(CO)2Fe-BmCr(CO)3 (6), Cr(CO)3Bm-CpmFe(CO)2CH2Ph (7), where Cp = 5-C5H5, Cpm = 15-C5H4, Bm = 16-C6H5. Temperature-dependent FTIR spectra were measured inn-pentane solutions over a wide temperature range and in the low-temperature solid matrices of argon and nitrogen. Rotamers, formed due to rotation about the metal-carbon -bond, were found in solutions and matrices. A molecular mechanics calculation of1 proved the possibility of such rotation.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1952–1956, November, 1994.The authors are grateful to the Russian Foundation for Basic Research (project code No 93-03-18592) and to the International Science Foundation (project code No MEQ000). 相似文献
84.
《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1997,53(14):2553-2557
Photolysis of 2-nitrobenzyl methyl ether in Ar and N2 matrices at 12 K generated an intermediate with λmax at 430 nm, and which was itself photolabile at 430–460 nm. Matrix IR spectra, as well as the UV-visible absorption, were obtained for this species. An analogous intermediate had previously been observed in flash-photolysis studies of 2-nitrobenzyl 4-cyanophenyl ether, and had been assigned an o-quinonoid structure on the basis of its kinetic behaviour and the position of its UV-visible absorption. In the matrix studies with 2-nitrobenzyl methyl ether, the IR spectra confirmed the o-quinonoid structure. 相似文献
85.
溶液成膜的温度对聚对苯二甲酸乙二酯结晶度的影响 总被引:1,自引:2,他引:1
<正> 用溶液成膜是制备聚合物薄膜的常用方法之一。但是溶液成膜的条件,如成膜温度,溶液浓度等对半结晶聚合物结晶度的影响研究报道较少。制备聚对苯二甲酸乙二酯(PET)非晶态薄膜通常使用熔融热压其后淬火的方法。由于PET在熔点附近易于降解,在薄膜中产生气泡,因而很难制备较大面积的均一厚度的薄膜,如在拉伸试验中所需 相似文献
86.
Studies of the vibrational spectra of matrix-isolated M+NO
3
–
ion pairs have been extended to glassy aprotic solvents. The deuterated form of the solvents DMSO, THF, and ACN have windows through the 7- nitrate ionv
3(e) mode infrared region, so it was possible to clearly observe the splitting of the degeneracy of this mode,v
3, produced by the contacting, but solvated, alkali metal cation. Primary attention has been directed to the extent to which this splitting is reduced relative to the argon matrix values. This reduction, which reflects electron-density transfer from the solvating molecules to the ion pairs, is comparable to that observed for H2O and NH3 matrices as the splitting is reduced to 20–35% of the argon-matrix values. The extent of reduction ofv
3 for the different solvents has been related to Gutmann's donicity number scale with the correlation holding well for solvent molecules of comparable size, DMSO, THF and DMF, but breaking down for the smaller linear ACN, apparently because of more molecules in the cation solvation sphere. The matrix data have also been used, through comparison with spectra for saturated liquid solutions of Li+NO
3
–
, to show that the contact ion pair is the dominant species in liquid THF and ACN, whereas the ions are largely solvent separated in DMSO. 相似文献
87.
B. L. Tumanskii V. V. Bashilov N. N. Bubnov S. P. Solodovnikov V. I. Sokolov 《Russian Chemical Bulletin》1994,43(5):884-886
Using ESR spectroscopy, the reaction of P(O)(OPri)2 phosphoryl radicals with C60ML2 (M=Pd, Pt) was studied and the spin-adducts formed were shown to be unstable under the reaction conditions. The 5-addition of Pt(PPh3)4 to the dimer of phosphorylfullerenyl radicals results in metal-containing dimers (RO)2(O)PL2MC60-C60ML2P(O)(OR)2, which dissociate when exposed to visible light to afford C60ML2P(O)(OR)2 radicals; ML2 in these complexes is located in different positions in relation to the radical center. As a result, the ESR spectra contain the superposition of at least five signals of radicals that differ in HFS constants andg-factors.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 938–940, May, 1994.The present work was supported by the Russian Foundation for Basic Research (Projects 93-03-18725 and 93-03-4101). 相似文献
88.
The gas-phase electronic absorption spectra of (6-C6R6)2Cr (R = Me (1) and Et (2)) reveal Rydberg structures, which disappear on going to the condensed phase. Each spectrum shows a Rydberg series converging to the ionization threshold. The first ionization potential determined as the series convergence limit is 4.662±0.008 eV for 1 and 4.667±0.019 eV for 2. The Rydberg bands are due to the transitions from the non-bonding MO 3dz2 to the R4s and Rnp (n = 4—10) levels. The influence of methyl and ethyl substituents on the term values of the Rydberg transitions depends on the principal quantum number of the Rydberg MO. 相似文献
89.
Unicyclic Graphs with Minimal Energy 总被引:7,自引:0,他引:7
Yaoping Hou 《Journal of mathematical chemistry》2001,29(3):163-168
If G is a graph and 1,2,...,
n
are its eigenvalues, then the energy of G is defined as E(G)=|1|+|2|++|
n
|. Let S
n
3 be the graph obtained from the star graph with n vertices by adding an edge. In this paper we prove that S
n
3 is the unique minimal energy graph among all unicyclic graphs with n vertices (n6). 相似文献
90.
Three new serratanes were isolated from the nonsaponifiable fraction of western white pine ( Dougl.) bark. The compounds were shown to be 3β-methoxyserrat-14-ene-21α,30-diol (), 3β-methoxyserrat-14-ene-21α, 29-diol (), and 3β-methoxyserrat-14-ene-21β,30-diol (), by a combination of chemical, and spectral methods. 相似文献