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91.
Reproducibility for successive determinations with a hanging mercury drop electrode is assessed in relation to solution stirring, drop size and back-diffusion to the mercury thread. The effect of experimental parameters such as drop size, deposition time and gallium concentration on the observed stripping current is investigated. The interference of zinc present in a 0.5M NaSCN + 4.2M NaClO(4) supporting electrolyte on the gallium detection limit and calibration plots is described. Formation of an intermetallic compound with a Zn:Ga ratio of 2:3 and its destruction by co-deposition of zinc with Sb are reported. A detection limit of 10(-8)M gallium was obtained in the presence of 10(-5)M Sb(III). 相似文献
92.
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94.
Summary The complexestrans-[Ru(NH3)4(H2O)PPh3](PF6)2 and [Ru(NH3)5L](PF6)2, (L=AsPh3 or SbPh3) have been isolated and characterized by microanalysis, cyclic voltammetry and ultraviolet-visible spectroscopy. The specific rate constants for the aquation of [Ru(NH3)5L]2+ totrans-[Ru(NH3)4L(H2O)]2+ are (2.5±0.1)×10–5s–1 and (1.8±0.1)×10–5s–1 for L=AsPh3 and SbPh3, respectively, at 25.0±0.1°C; =0.10 mol dm–3, NaO2CCF3. Under the same conditions, the second-order rate constants for the substitution of water intrans-[Ru(NH3)4(H2O)L]2+ by isonicotinamide (isn) are 1.2±0.1, (6.3±0.3)×10–2 and (3.8±0.2)×10–2
m
–1s–1 for L=PPh3, AsPh3, and SbPh3, respectively, suggesting that the order of decreasingtrans-effect is: PPh3AsPh3>SbPh3. The formation constants for thetrans-[Ru(NH3)4L(isn)]2+ complexes are 75±3, (1.40±0.01)×103 and (1.80±0.02)×103M–1 for L=PPh3, AsPh3, and SbPh3, respectively, suggesting that the order of increasingtrans-influence is: SbPh33PPh3. 相似文献
95.
The development of microplasmas for spectrochemical analysis by optical methods is discussed. Recent achievements in miniaturization are highlighted, especially for three types of plasmas, namely high-frequency plasmas, dc-discharges and microwave plasmas. The potentials of each of these groups of plasmas as sources for atomic emission spectrometry are discussed. Literature citations and experiments indicate that the plasmas are also very useful as atom reservoirs for atomic absorption spectrometry. Methods of sampling, including feeding with gas chromatography effluents, the use of electrothermal vaporization, and the evolution of gaseous species (as shown for the case of Hg vapor), are discussed as prominent interfaces to make use of these sources for elemental analysis. 相似文献
96.
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98.
Comparison of different fibers for the solid-phase microextraction of phthalate esters from water 总被引:3,自引:0,他引:3
Solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS) has been applied to determine six phthalate esters and one adipate ester in water. The SPME parameters were optimized for several commercially available fibers. A 65-microm polydimethylsiloxane-divinylbenzene (PDMS-DVB) was the fiber selected and was applied to analysis of water from the Ebro river and the industrial port of Tarragona. The studied compounds were found at concentrations ranging from 0.4 microg l(-1) for di-n-butyl phthalate ester (DnBP) to 3.2 microg l(-1) for bis(2-ethylhexyl) phthalate ester (DEHP). The linear range for real samples was from 0.1 to 10 microg l(-1) for most phthalates, and the limits of detection of the method were between 3 and 30 ng l(-1). Repeatability and reproducibility between days (n = 5) for 1 microg l(-1) samples were below 13 and 18%, respectively. 相似文献
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100.
Amorín M Castedo L Granja JR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(22):6543-6551
Here we report the preparation and structural characteristics of self-assembling peptide tubelets composed of 32-membered rings formed of alternating alpha-amino acids and cis-3-aminocyclohexanecarboxylic acids. The tubelets possess a partial hydrophobic core environment, provided by the projection of the cyclohexane C2 methylene moiety into the lumen, and a Van der Waals pore diameter of about 7 A. 相似文献