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71.
In this paper, 2-(2′-hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), a typical compound that exhibits excited state intramolecular proton transfer (ESIPT) reaction and possesses good photophysical properties, is synthesized and used as fluoroionophore for Fe3+ sensitive optochemical sensor. The decrease of fluorescence intensity of HPQ membrane upon the addition of Fe3+ was attributed to the blocking of ESIPT reactions of HPQ and quenching its fluorescence. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensor shows a linear response toward Fe3+ in the concentration range of 7.1 × 10−7 M to 1.4 × 10−4 M with a limit of detection of 8.0 × 10−8 M, and a working pH range from 2.5 to 4.5. It shows excellent selectivity for Fe3+ over a large number of cations such as alkali, alkaline earth and transitional metal ions. The proposed sensor is applied to the determination of the content of iron ions in pharmaceutical preparations samples with satisfactory results. 相似文献
72.
固氮酶及合成氨Fe催化剂中N2的络合位 总被引:1,自引:0,他引:1
用乙烯为探针研究了固氮酶中N2的键合位,结果表明,乙烯不能与N2在固氮酶体系中相竞争,提出N2在固氮酶中键合位很可能是蛋白键合FeMo-co笼内6Fe位的μρ(η^2,ε4)t 3Fe+1Mo位的μ4(η^3,ε)方式,而不是笼口2Fe位的μ2(η^2)方式,在合成氨Fe催化剂中N2的络事方式可能是μ6(η^3,ε3 )。 相似文献
73.
Keith A. Hunter Margaret R. Leonard Peter D. Carpenter J. David Smith 《Colloids and surfaces. A, Physicochemical and engineering aspects》1997,120(1-3):111-121
The kinetics of iron colloid aggregation in estuaries have been simulated with a model estuary in which seawater is continuously pumped into a reservoir initially containing river water. Profiles of colloidal Fe concentration versus salinity produced in this apparatus closely resembled field data for actual estuaries. Synthetic Fe colloids prepared by peptising Fe(OH)3 with humic acid and phosphate showed very similar kinetic behaviour. Aggregation rate was found to be almost independent of velocity shear rate, implying that most aggregations are induced by brownian interparticle collisions. A heterogeneous kinetic model is proposed to explain the kinetic behaviour of Fe colloids during seawater-induced aggregation. This model describes kinetic behaviour in terms of a log-normal distribution of rate constants characterised by a mean value k and a standard deviation γ. Experiments showed that k is linearly related to the rate constant for salinity increase during mixing. This coupling of salinity changes and aggregation rate leads to Fe-salinity profiles that are nearly independent of the rate of salinity change, but which are dependent on γ. 相似文献
74.
Linda L LipeSuzanne M Purinton Elizabeth MederiosC.Chad Harrell Cynthia EftaMelissa Murray Meredith WoodRay-Bernard Portier Stuart J Chalk 《Analytica chimica acta》2002,455(2):287-304
A new apparatus for mixing sample and reagent in flow injection analysis (FIA) is described. The continuously variable volume reactor (CVVR) replaces the conventional mixing coil in a flow injection (FI) manifold to provide mixing and dilution. A linear actuator motor allows control of the chamber volume via LabVIEW software. The chamber volume can be incremented in steps of 1 μl over the range 68-1704 μl. In addition, the chamber has an integral variable-speed stirring unit that is also under computer control. Experiments were performed to evaluate the dispersion characteristics of this new device, evaluate the volume reproducibility, and understand the mixing characteristics. Use of the chamber is shown in the determination of iron(II) in pond water, and in NIST SRM 1643d with excellent results and a detection limit of 3.7 μg/l iron(II). Advantages of the CVVR and future research activities using the device are discussed. 相似文献
75.
The thermochemical behavior of the coordination compound [Fe(urea)6](NO3)3 was studied by simultaneous CG–TG–DTG–DTA and mass spectrometry methods non-isothermal conditions. The compound decomposes at 200 °C into a mixture of spinel-type oxides and hematite. The nature and particle size of the final decomposition products are strongly associated with the conditions during the thermal treatments, in particular the heating rate and the calcination temperature. A certain fraction of the products are formed as nanometric particles; they show superparamagnetic behavior at room temperature. The comparably low temperature of the calcination treatments of this compound is a promising perspective to attain small sized magnetic powders. 相似文献
76.
77.
分光光度计测铁矿石中钛的测量不确定度评定 总被引:1,自引:0,他引:1
紫外-可见分光光度计在化学分析中应用较为广泛。对于借助其进行化学分析测量不确定度的评定,目前较多见于溶液测定。实际应用中,测试样品多为固体,涉及到称样、溶解、稀释、定容等步骤。此文试从随机效应和系统效应的角度考虑,对紫外-可见分光光度计应用ISO4691:1985铁矿石中钛含量的测定——二安替比林甲烷分光光度法对铁矿石中钛的测量过程中的不确定度来源进行了较为全面的分析,并最终给出评定结果。 相似文献
78.
Iron interference in the spectrophotometric catalytic determination of molybdenum based on the iodide-hydrogen peroxide reaction can be corrected by using sulphosalicylic acid as masking and color-forming reagent. The catalytic influence of iron ions is circumvented to the extent of about 90% and correction of any remaining iron ions is possible by monitoring the colored iron(III)-salicylate complex at 490 nm. In this way, iron is also determined. With the proposed system, molybdenum can be determined in plant and food digests within the 0–100 μg Mo 1−1 range in the presence of up to 25 mg Fe 1−1, at a sampling rate of about 50 determinations h−1. The relative standard deviation of 10 consecutive measurements was estimated as < 2%. Results for samples were comparable with those obtained by graphite furnace atomic absorption spectrometry. In addition, recoveries within the range 94–100% were calculated. 相似文献
79.
A series of 2,6-bis(imino)pyridyl iron(II) and cobalt(II) complexes [2,6-(ArNCMe)2C5H3N]MCl2 (Ar = 2,6-i-Pr2C6H3, M = Fe: 3a, M = Co: 4a; Ar = 2,4,6-i-Pr3C6H2, M = Fe: 3b, M = Co: 4b; Ar = 2,6-i-Pr2-4-BrC6H2, M = Fe: 3c, M = Co: 4c; Ar = 2,4-i-Pr2-6-BrC6H2, M = Fe: 3d, M = Co: 4d) has been synthesized, characterized, and investigated as precatalysts for the polymerization of ethylene in the presence of modified methylaluminoxane (MMAO). The substituents of pyridinebisimine ligands and their positions located significantly influence catalyst activity and polymer property. It is found that the catalytic activities of the iron complexes/MMAO systems are mainly dominated by electronical effect, while those of the cobalt complexes/MMAO systems are primarily controlled by hindering effect. 相似文献
80.
Several novel substituted bis(2‐pyridylimino)isoindolato (BPI) cobalt(II) and iron(II) complexes [M(BPI)(OAc)(H2O)] (M = Co: 1 ‐ 6, Fe: 7) have been synthesized by reaction of bis(2‐pyridylimino)isoindole derivatives with the corresponding metal(II) acetates. Reaction of 1‐6 with 1.5 ‐ 2 molar equivalents of t‐BuOOH gave the corresponding alkylperoxocobalt(III) complexes [Co(BPI)(OAc)(OOtBu)] (10 ‐ 15). Using an aqueous solution of t‐BuOOH (70 %), cyclohexene was selectively catalytically oxidized to the dialkylperoxide cyclohex‐2‐ene‐1‐t‐butylperoxide. 相似文献