Total reflection X-ray fluorescence (TXRF) analysis after the separation of matrix element was studied for the determination
of trace impurity elements (Ca, Sc, V, Cr, Mn, Fe, Co, Ni and Zn) in high purity copper. Matrix copper was removed by electrolysis
(0.2 A, 8 h) of a nitric acid solution. A 10 μL aliquot of the remaining solution of the electrolysis was dropped on a silicon-wafer
sample-carrier and dried in a vacuum. This was repeated five times and the precipitate of five 10 μL-aliquots was analyzed
by TXRF using a W-Lβ beam with an incident angle of 0.05 °. TXRF analytical values were obtained by using relative sensitivity
factors of the analytes to the internal standard element (Pd). Detection limits of the analytes ranges from 0.077 ng for Zn
to 0.785 ng for Ca.
Received: 25 December 1997 / Revised: 30 March 1998 / Accepted: 2 April 1998 相似文献
In the presence of a catalytic amount of Cu(OTf)(2)-chiral diamine 3e complex, N-acylimino esters reacted with silyl enol ethers to afford the corresponding Mannich-type adducts in high yields with high enantioselectivities. A wide variety of silyl enol ethers derived from ketones, as well as esters and thioesters, reacted smoothly. In the reactions of alpha-substituted silyl enol ethers (alpha-methyl or benzyloxy), the desired syn-adducts were obtained in high yields with high diastereo- and enantioselectivities. Several intermediates for the synthesis of biologically important compounds were prepared using this novel catalytic asymmetric Mannich-type reaction, and at the same time, absolute and relative stereochemical assignments were made. In addition, it has been revealed that alkyl vinyl ethers reacted with N-acylimino esters in the presence of a catalytic amount of the Cu(II) catalyst to give the corresponding Mannich-type adducts in high yields with high enantioselectivities. This is the first example of catalytic asymmetric Mannich-type reactions with alkyl vinyl ethers. The reaction mechanism, structure of chiral catalyst-electrophile complexes, and transition states of these catalytic asymmetric reactions were assumed based on X-ray crystallographic analysis of the Cu(II)-chiral amine complex, PM3 calculations, and FT-IR analyses, etc. Finally, (1R,3R)-N-(3-hydroxy-1-hydroxymethyl-3-phenylpropyl)dodecanamide (HPA-12, 1), a new inhibitor of ceramide trafficking from endoplasmic reticulum to the site of sphingomyerin (SM) synthesis, has been synthesized efficiently using the present Mannich-type reaction as a key step. The synthesis involved three steps (two-pot), and total yield was 82.9%. 相似文献
IntactPhormidium sp. cells, immobilized on a SnO2 semiconductor electrode, are capable of transferring electrons to SnO2 in a light-dependent reaction. Drying a “wet” algal electrode at 50°C for 60 min increases photocurrent output capacity by 100-fold. We have studied the effect of various parameters on photocurrent generation. The magnitude of the photocurrent increased with increasing light intensity and depended on the nature of the electrolyte solution. The output, about 8 μA 10 μg Chl?1 cm+2, was obtained using 50 mM H3BO3?Na2CO3?KCl buffer as an electrolyte, an irradiance (>460 nm) of 250 J/m2, and potentiostatic conditions (the algal working electrode was poised at +0.6 V vs a saturated calomel electrode). The yield was more than doubled upon addition of an electron carrier, such as methyl viologen, benzyl viologen, or Vitamin K3, to the electrolyte solution. Maximum photocurrent was obtained at around pH 8 and 45°C, which are optimal conditions for growth of the cyanobacterium. Furthermore, DCMU, an inhibitor of photosynthetic electron flow, drastically decreased the yield, as did heat treatment of the electrode at 110°C for 15 min. The photocurrent action spectrum peak coincided well with the absorption peak of the light-harvesting pigment, phycocyanin. These results support the idea that electron transfer can occur across algal cell walls from the source of the light-induced reactions located within the lamellar membranes to the semiconductor electrode. 相似文献
Direct dissolution agents of calcium bilirubinate gallstones were prepared by dissolving chelating agents in aqueous solutions of sodium carbonate containing polar solvent. Dissolution experiments on a calcium bilirubinate disk as a model of a gallstone were performed using a static disk method.
From the amounts dissolved in an hour using dissolution agents with various composition, the most effective conditions for dissolving calcium bilirubinate were determined as follows: (1) the higher the pH of the dissolution agent, the more calcium bilirubinate was dissolved. Thus, pH 8.4 was chosen as the best pH condition within the range of harmless usage to the human body in vivo in limited amount; (2) a combination of ethylenediaminetetraacetic acid (EDTA) as chelating agent for calcium and 1,3-dimethyl-2-imidazolidinone (DMI) as polar solvent; (3) in the mixed system of EDTA and DMI, the most effective concentrations were about 4 wt.% EDTA and about 30 wt.% DMI.
The dissolution agent satisfying the above conditions gave a dissolved amount of about 70 mg dl−1 in 1 h. This amount was considerably higher than those using DMI and EDTA independently. This suggests that dissolution is due to cooperation between EDTA and DMI. 相似文献
We have developed a new experimental apparatus for performing coincidence measurements of the ions desorbed and projectiles scattered from the surfaces of noble gas solids by slow multiply charged ion impacts at grazing incidence angles. This simultaneously measures the desorbed ions' flight times and the scattered projectiles' charge states. We also conduct experiments on 6 keV Ar6+ impacts onto a solid Ne surface using the device. 相似文献
We describe here carbanion reactions using catalytic amounts of bases. The carbanions formed are different from conventional carbanions in which stoichiometric amounts of bases are needed for the formation. Two types of reactions using such carbanions from amide (imido) and ester equivalents are discussed. 相似文献
Diazo(trimethylsilyl)methylmagnesium bromide reacted with (o-methoxyphenyl)(oxo)acetates to readily afford 2-unsubstituted benzofuran-3-carboxylates via oxonium ylides formed from the initially generated alkylidenecarbene intermediates. 相似文献
An ultraintense laser injected a 10 J of power at 1.053 microm in 0.5 ps into a glass capillary of 1 cm long and 60 microm in diameter and accelerated plasma electrons to 100 MeV. One- and two-dimensional particle codes describe wakefields with 10 GV/m gradient excited behind the laser pulse, which are guided by a plasma density channel far beyond the Rayleigh range. The blueshift of the laser spectrum supports that a plasma of 10(16) cm(-3) is inside the capillary. A bump at the high energy tail suggests the electron trapping in the wakefield. 相似文献
This paper reports on the novel electropolymerization of an immiscible monomer, such as 3,4-ethylenedioxythiophene (EDOT), in aqueous electrolytes using acoustic emulsification. This new methodology has many practical advantages and characteristics: (a) the formation of stable monomer droplets in aqueous electrolytes without added surfactants using ultrasonic treatment; (b) very smooth electropolymerization in aqueous electrolytes via the direct electron transfer between the electrode and the immiscible monomer droplets; (c) good conductivity after doping of the polymer film formed. 相似文献