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71.
Immobilized sulfhydryl groups were prepared by partial thiolation of NH2-glass beads. The microenvironment of the immobilized SH groups was varied by different chemical modifications of neighboring
NH2 groups. Introduction of a strong charge in the surroundings of immobilized sulfhydryls results in their dramatic stabilization
against autooxidation. This effect is due to the salting of O2 from the surface microlayer of the thiolated beads. 相似文献
72.
Pentaazadienido Complexes of Zinc, Cadmium, and Mercury. The Crystal Structure of [Cd(EtOC6H4-N5-C6H4OEt)2(py)2] and [Hg(tol-N5-tol)2(py)] The pentaazadienido complexes [M(EtOC6H4N5C6H4OEt)2] (M = Zn ( 1 ), Cd ( 2 )) are formed by the reaction of [M(NH3)4]2+ with [EtOC6H4N5C6H4OEt]? in aqueous ammonia. 2 crystallizes from pyridine as [Cd(EtOC6H4N5C6H4OEt)2py2] ( 3 ) with the triclinic space group P1 and a = 937.2(2); b = 1422.7(2); c = 2085.5(2) pm; α = 75.28(1)°; β = 94.74(1)°; γ = 99.75(1)°; Z = 2. The central Cd2+ ion of 3 exhibits an octahedral coordination by two pyridine ligands in cis arrangement and two (N1, N3)-2+ chelating pentaazadienide ions. The reaction of [HgI4]2 with the 1,5-di(tolyl)pentaazadienide anion in aqueous ammonia affords [Hg(p-tol-N5-tol)2] ( 4 ), which crystallizes from pyridine in form of [Hg(tol-N5-tol)2py] ( 5 ) with the space group P1 and a = 1176.2(4); b = 1203.1(3); c = 1295.6(5) pm; α = 100.77(3)°; β = 110.08(3)°; γ = 94.29(2)°; Z = 2. In 5 the Hg2+ cation is threefold coordinated by two monodentate (N3)-η1 pentaazadienid anions and one pyridine ligand. Within the N5 chains of the pentaazadienid anions of 3 and 5 localized N? N double bonds are found in the positions N1? N2 and N4? N5 with distances between 125 and 129 pm. 相似文献
73.
富镉Hg_(1-x)Cd_xTe是一种新型的光电转换材料,已用于固体结太阳能光伏电池:ITO/CdS/Hg_(1-)Cd_xTe/Au。我们曾对Hg_(1-x)Cd_xTe的电沉积机理作过研究。最近我们用电沉积制备的Hg_(0.09)Cd_(0.91)Te多晶薄膜做成了液体结太阳能光电化学电池并观察到明显光电响应。 相似文献
74.
鼻咽癌患者治疗过程中头发微量元素的变化 总被引:1,自引:0,他引:1
对比了30名健康人与100名初诊、三个月后复诊及六个月后复诊的鼻咽癌患者头发中的11种微量元素的含量。发现病人的锌(Zn)、铜(Cu)、锰(Mn)及钴(Co)的含量都比健康人低,而病人的钛(Ti)及砷(As)含量则偏高。但经过三至六个月电疗及化疗之后,这些元素的含量普遍与健康人差异变小,这似乎是成功治疗的一个反映。 相似文献
75.
G. Stringari Ivo Pancheri Frank Möller Osvaldo Failla 《Accreditation and quality assurance》1998,3(3):122-126
Chemical analyses of trace elements are affected by relatively high analytical errors due to the different steps of the laboratory
procedures: samples grinding, mineralisation and instrumental measurements. In the present communication, the influence of
the grinding phase on the global uncertainty of Pb, Cd, Ni and Cr determinations in plant samples by the classical method
of atomic absorption spectrometry/electrothermal atomisation (AAS-ETA) after dry ashing is quantified. Two grinding machines,
a planetary mill with balls and jars of agate versus a stainless steel grinder were compared by analysing leaf samples of
cucumber, strawberry, kiwivines, apple trees and grapevines from agricultural experimental plots under controlled conditions.
Variance components due to the difference between grinding methods and experimental plots were estimated. Further, the simultaneous
effects of the grinding methods on all considered metals have been evaluated by analysis of variance. With the stainless steel
grinder, on average, higher levels of the considered heavy metals were obtained (up to 67% of the mean values). On average,
the increments were similar for metals contained in steel (Ni and Cr) and those not contained (Pb and Cd). The true causes
of these differences need further investigation to determine whether the higher metal detection is due to possible contamination,
to a different grinding quality or to other reasons. Finally, the grinding methods did not seem to affect the combined uncertainty
of the analyses.
Received: 3 November 1997 · Accepted: 29 November 1997 相似文献
76.
E. N. Ushakov L. G. Kuz’mina A. I. Vedernikov M. S. Kapichnikova J. A. K. Howard M. Wörner A. M. Braun M. V. Alfimov S. P. Gromov 《Russian Chemical Bulletin》2006,55(1):94-100
The structures of new butadienyl dyes of the benzothiazole series containing the dithia-15-crown-5 (2a) or dithia-18-crown-6 (2b) fragments were established by X-ray diffraction. Complexation of dyes 2a,b with Hg2+, Pb2+, Cd2+, Ag+, Zn2+, and alkaline-earth cations in aqueous-acetonitrile solutions was studied by spectrophotometry. At a high percentage of water
in solutions (P
w ≈ 50%), these dyes have a very low ability to bind Pb2+ cations (logK < 2) and virtually do not bind Cd2+, Zn2+, and alkaline-earth cations. At the same time, these dyes form stable 1: 1 complexes with Hg2+ and Ag+ cations at all P
w. The stability constants of complexes with the Ag+ cation increase with increasing P
w because the free energy of hydration of this cation is much lower than the free energy of solvation in acetonitrile. In the
P
w range from 0 to 75%, the stability constants of the complexes of dyes 2a,b with the Hg2+ cation are larger than those of the corresponding complexes with the Ag+ cation by more than four orders of magnitude.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 90–96, January, 2006. 相似文献
77.
Christos Kokkinos Anastasios Economou Ioannis Raptis Constantinos E. Efstathiou Thanasis Speliotis 《Electrochemistry communications》2007,9(12):2795-2800
This work describes a novel type of bismuth electrode for stripping voltammetry based on coating a silicon substrate with a thin bismuth film by means of sputtering. The bismuth-based sensors were characterized by optical methods (scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD)) and as well as by linear sweep voltammetry. Subsequently, the electrodes were tested for the detection of low concentrations of trace metals (Cd(II), Pb(II) and Ni(II)) by stripping voltammetry. Well-formed stripping peaks were observed for trace concentrations of the target analytes demonstrating “proof-of-principle” for these sensors. This type of electrochemical device, utilizing thin-film technology for the formation of the bismuth film, holds promise for future applications in trace metal analysis. 相似文献
78.
脊髓小脑变性疾病病人血清铜,锌,铝,铁含量的研究 总被引:1,自引:0,他引:1
脊髓小脑变性疾病(SCD)的病因可能与遗传、神经生化紊乱、感染、微量元素平衡障碍及自由基损伤等因素有关,其中微量元素平衡障碍的研究具有重要意义。检测了SCD中发病率较高的橄榄桥小脑萎缩症(OPCA)及晚发性小脑皮质萎缩症(LCCA)病人15例血清中铜、锌、铝、铁等微量元素含量。发现病人比对照组铜明显降低,P〈0.01;锌明显降低,P〈0.01;铝明显升高,P〈0.01;铁无明显差别。 相似文献
79.
The microwave-assisted acid-digestion for the determination of metals in coal by ICP-AES was investigated, especially focusing on the necessity of adding HF. By testing five certified reference materials, BCR-180, BCR-040, NIST-1632b, NIST-1632c, and SARM-20, it was found that the two-stage digestion without HF (HNO3 + H2O2 was used) was very effective for the pretreatment of ICP-AES measurement. Both major metals (Al, Ca, Fe, and Mg) and minor or trace metals (Co, Cr, Cu, Mn, Ni, Pb, and Zn) in coal gave good recoveries for their certified or reference values. The possibility of ‘HF-memory effect’ was cancelled by the use of a set of vessels which had been never contacted with HF. Twenty-four Japanese standard coals (SS coals) were analyzed by the present method, and the concentrations of major metals measured by the present method provided very high accordance with those from the authentic JIS (Japanese Industrial Standard) method. 相似文献
80.
Ignacio López-García Mateo Sánchez-Merlos Manuel Hernández-Córdoba 《Spectrochimica Acta Part B: Atomic Spectroscopy》1997,52(14):378-2092
A graphite furnace atomic absorption spectrometric procedure for the determination of mercury is presented, in which the samples are suspended in a solution containing hydrofluoric and nitric acids. Silver nitrate (4% m/v) and potassium permanganate (3%) are incorporated, in the order specified, and aliquots are directly introduced into the graphite furnace. A fast heating programme with no conventional pyrolysis step is used. The detection limit for mercury in a 125 mg ml−1 suspension is 0.1 μg g−1. Calibration is performed by using aqueous standards. The reliability of the procedure is proved by analysing certified reference materials. 相似文献