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201.
计算了43种不对称变色酸双偶氮膦酸型显色剂的Am拓扑指数,并将其与结构选择性因子相结合,用于偶氮类显色剂结构与铈显色反应对比度的相关性研究,讨论了显色剂结构对拓扑指数有译比度的影响。 相似文献
202.
依据系统工程理论的原理和方法,研究了Sr、B、Zn、Mo、Cu五种微显元素对中甘11号结球甘蓝产量、品质的影响及各因子间的复合效应。试验结果表明,各因子对中甘11号产量的作用是:Sr>B>Zn>Cu>Mo。获得了中甘11号亩产在6000kg以上的优化组合方案是:Sr0.054%~0.061%,B0.035%~0.042%,Zn0.047%~0.057%,Mo0.032%~0.038%,Cu0.050%~0.056%,为微量元素在蔬菜上的应用提供了科学依据. 相似文献
203.
Electropolymerization of 3,3′-diaminobenzidine on a gold surface gave an adherent, stable film of poly(3,3′-diaminobenzidine) (PDAB). This polymer film retained the complexational functionalities of its monomer, demonstrating preconcentration abilities for several ions, including Se(IV) and Te(IV). In particular, in this work, continuous flow and flow injection methods were developed for the sensitive and selective determination of Te(IV). The optimized method for the continuous flow mode had a detection limit of 5.6×10−9 mol l−1 for 10 min preconcentration. Typical relative standard deviations for six consecutive determinations were 1.82 and 2.56% for Te(IV) concentrations of 1.0×10−6 and 5.0×10−8 mol l−1, respectively (10 min preconcentration). The method was applied to the determination of Te(IV) in real samples. 相似文献
204.
微量元素锌促进儿童生长发育临床研究 总被引:1,自引:0,他引:1
报道以微量元素锌治疗缺锌患儿118例并与114例作对照观察.结果发现,衡量生长发育与营养的敏感指标:身高、体重、血清白蛋白及血色素等参数,治疗组比对照组都显著提高(P值<0.01).证明锌制剂对缺锌儿童有显著的促进生长发育及改善营养状态作用,作者并对锌的作用机理作了论述. 相似文献
205.
Indium(III) chloride forms in water with potassium 1,2‐dithiooxalate (dto) and potassium 1,2‐dithiosquarate (dtsq) stable coordination compounds. Due to the higher bridging ability of the 1,2‐dithiooxalate ligand in all cases only thiooxalate bridged binuclear complexes were found. From 1,2‐dithioquadratate with an identical donor atom set mononuclear trischelates could be isolated. Five crystalline complexes, (BzlMe3N)4[(dto)2In(dto)In(dto)2] ( 1 ), (BzlPh3P)4[(dto)2In(dto)In(dto)2] ( 2 ), (BzlMe3N)3[In(dtsq)3] ( 3 ), (Bu4N)3[In(dtsq)3] ( 4 ) and (Ph4P)[In(dtsq)2(DMF)2] ( 5 ), have been isolated and characterized by X‐ray analyses. Due to the type of the complex and the cations involved these compounds crystallize in different space groups with the following parameters: 1 , monoclinic in P21/c with a = 14.4035(5) Å, b = 10.8141(5) Å, c = 23.3698(9) Å, β = 124.664(2)°, and Z = 2; 2 , triclinic in P with a = 11.3872(7) Å, b = 13.6669(9) Å, c = 17.4296(10) Å, α = 88.883(5)°, β = 96.763(1)°, γ = 74.587(5)°, and Z = 1; 3 , hexagonal in R3 with a = 20.6501(16) Å, b = 20.6501(16) Å, c = 19.0706(13) Å and Z = 6; 4 , monoclinic in P21/c with a = 22.7650(15) Å, b = 20.4656(10) Å, c = 14.4770(9) Å, β = 101.095(5)°, and Z = 4; 5 , triclinic in P with a = 9.2227(6) Å, b = 15.3876(9) Å, c = 15.5298(9) Å, α = 110.526(1)°, β = 100.138(1)°, γ = 101.003(1)°, and Z = 2. 相似文献
206.
The new 10 μg l−1 arsenic standard in drinking water has been a spur to the search for reliable routine analytical methods with a limit of detection at the μg l−1 level. These methods also need to be easy to handle due to the routine analyses that are required in drinking water monitoring. Graphite furnace atomic absorption spectrometry (GFAAS) meets these requirements, but the limit of detection is generally too high except for methods using a pre-concentration or separation step. The use of a high-intensity boosted discharge hollow-cathode lamp decreases the baseline noise level and therefore allows a lower limit of detection. The temperature program, chemical matrix modifier and thermal stabilizer additives were optimized for total inorganic arsenic determination with GFAAS, without preliminary treatment. The optimal furnace program was validated with a proprietary software. The limit of detection was 0.26 μg As l−1 for a sample volume of 16 μl corresponding to 4.2 pg As. This attractive technique is rapid as 20 samples can be analysed per hour. This method was validated with arsenic reference solutions. Its applicability was verified with artificial and natural groundwaters. Recoveries from 91 to 105% with relative standard deviation <5% can be easily achieved. The effect of interfering anions and cations commonly found in groundwater was studied. Only phosphates and silicates (respectively at 4 and 20 mg l−1) lead to significant interferences in the determination of total inorganic arsenic at 4 μg l−1. 相似文献
207.
ICP-AES determination of trace elements after preconcentrated with p-dimethylaminobenzaldehyde-modified nanometer SiO2 from sample solution 总被引:1,自引:0,他引:1
A new method that utilizes p-dimethylaminobenzaldehyde-modified nanometer SiO2 (SiO2-p-DMABD) as a solid phase extractant has been developed for simultaneous preconcentration of trace Cr(III), Cu(II), Fe(III) and Pb(II) prior to the measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). The preconcentration conditions of analytes were investigated, including the pH value, the shaking time, the mass of sorbent, the sample flow rate and volume, the elution condition and the interfering ions. The adsorption capacity of nanometer SiO2-p-DMABD was found to be (mg g− 1) Cr(III): 6.2, Cu(II): 18.6, Fe(III): 4.7 and Pb(II): 6.0 at pH 4. The adsorbed metals were quantitatively eluted with 4 mL of 1.0 mol L− 1 HCl. According to the definition of IUPAC, the detection limits (3σ) of this method for Cr(III), Cu(II), Fe(III) and Pb(II) were 0.79, 1.27, 0.40 and 1.79 ng mL− 1, respectively. The proposed method achieved satisfied results when it was applied to the determination of trace Cr(III), Cu(II), Fe(III) and Pb(II) in biological and water samples. 相似文献
208.
Compounds A3M5 (A = alkaline earth, M = triel/tetrel): A Case Study on Structural and Electronic Factors Stabilizing Polar Intermetallics Starting from the non electron precise binary compounds Ca3Ga5/Sr3In5 (Hf3Ni2Si3 type) and Ba3Al5 at one hand and Ba3Pb5 (Pu3Pd5 type) at the other hand, a series of new ternary intermetallics of the general formula A3M5 (A: alkaline earth, M: triel/tetrel) has been synthesized, structurally characterized and studied by band structure calculations. The chemical substitution of M in A3M5 allows, via the continous variation of the radius ratio (rA:rM) and the valence electron number (VE/M) the detection of the geometrically and electronically determined stability ranges of the three structure types formed by the binary compounds. At values of rA:rM between 1.30 and 1.52 in the triel rich region of A3M′xM″5?x the Hf3Ni2Si3 type (orthorhombic, space group Cmcm) is formed: In Ca3Ga5 up to 1.8 Ga can be substituted by Al, in Sr3In5 similar amount of In can be replaced by either Al or Ga. The mixed trielide Sr3Al2.6Ga2.4 (a = 468.4(1), b = 1132.5(1), c = 1570.0(2) pm, R1 = 0.0261) can be obtained, although both corresponding binary phases are not known. At larger values of the ratio rA/rM as in Ba3Al3Ga2 (Ba3Al5 type, hexagonal, space group P63/mmc, a = 598.9(1), c = 1456.0(3) pm, R1 = 0.0353) layers of condensed M5 building blocks with Al‐Al partial bonds are formed. Substituting one In position in Sr3In5 against Pb results in the isotypic, but electron precise Zintl compound Sr3In4Pb (a = 506.1(1), b = 1191.8(3), c = 1650.2(4) pm, R1 = 0.0286), where the Fermi level in shifted into a distinct minimum of the density of states. Conversely, at the tetrele rich end of the series A3InxPb5?x, characterized by compounds of the Pu3Pd5 type (orthorhombic, space group Cmcm) with almost isolated nido clusters M5, a minimum of the DOS can be reached, if Pb is partially substituted by In (A3InxPb5?x with A = Sr/Ba: x = 0.7/0.6; a = 1084.6(2)/1118.6(2), b = 867.1(2)/904.4(1), c = 1104.8(2)/1133.9(2) pm, R1 = 0.0394/0.0434). 相似文献
209.
Thomas Müller 《Silicon Chemistry》2007,3(3-4):123-130
Quantum mechanical calculations at the B3LYP/6-311+G(d,p) and MP2/6-311+G(d,p) level of theory reveal that higher congeners
of the aromatic imidazolium ion, e.g. 2-E-imidazolium ions (E = Si, Ge, Sn), adopt either planar or pyramidal structures,
depending on the substituent R
2 attached to the element and on the group 14 element itsself. In the case of 2-silaimidazolium ions chemically significant
energy differences in favour of non-planar cations are predicted only for strongly σ-electron withdrawing substituents R
2 such as F or CF3. The pyramidalization computed for the germanium and tin analogues are however significant for all investigated substituents
R
2 and are accompanied by a substantial stabilization compared to the corresponding planar structures. A detailed bonding analysis
reveals that the non-planar cations are best described as complexes of monovalent group 14 element cations R
2E+ with the diazabutadiene ligand. 相似文献
210.
To improve the reproducibility, stability, and sensitivity of bismuth film electrode (BiFE), we studied the performances of a mixed coating of two cation‐exchange polymers, Nafion (NA) and poly(sodium 4‐styrenesulfonate) (PSS), modified glassy carbon BiFE (GC/NA‐PSS/BiFE). The characteristics of GC/NA‐PSS/BiFE were investigated by scanning electron microscopy and cyclic voltammetry. Various parameters were studied in terms of their effect on the anodic stripping voltammetry (ASV) signals. Under optimized conditions, the limits of detection were 71 ng L?1 for Cd(II) and 93 ng L?1 for Pb(II) with a 10 min preconcentration. The results exhibited that GC/NA‐PSS/BiFE can be a reproducible and robust tool for monitor of trace metals by ASV rapidly and environmentally friendly, even in the presence of surface‐active compounds. 相似文献