Plasma direct current

Inductively coupled plasma (icp) emission, direct current plasma (dcp), and inductively coupled plasma mass spectrometry (icp/ms) have taken over as the methods of choice for the simultaneous detection of metallic impurities in hafnium and hafnium compounds (29,30). 

Instrumental Quantitative Analysis. Methods such as x-ray spectroscopy, oaes, and naa do not necessarily require pretreatment of samples to soluble forms. Only reUable and verified standards are needed. Other instmmental methods that can be used to determine a wide range of chromium concentrations are atomic absorption spectroscopy (aas), flame photometry, icap-aes, and direct current plasma—atomic emission spectroscopy (dcp-aes). These methods caimot distinguish the oxidation states of chromium, and speciation at trace levels usually requires a previous wet-chemical separation. However, the instmmental methods are preferred over (3)-diphenylcarbazide for trace chromium concentrations, because of the difficulty of oxidizing very small quantities of Cr(III). 

The XRD and TEM showed that the bimetallic nanoparticles with Ag-core/Rh-shell structure spontaneously form by the physical mixture of Ag and Rh nanoparticles. Luo et al. [168] carried out structure characterization of carbon-supported Au/Pt catalysts with different bimetallic compositions by XRD and direct current plasma-atomic emission spectroscopy. The bimetallic nanoparticles were alloy. Au-core/Pd-shell structure of bimetallic nanoparticles, prepared by co-reduction of Au(III) and Pd(II) precursors in toluene, were well supported by XRD data [119]. Pt/Cu bimetallic nanoparticles can be prepared by the co-reduction of H2PtClg and CuCl2 with hydrazine in w/o microemulsions of water/CTAB/ isooctane/n-butanol [112]. XRD results showed that there is only one peak in the pattern of bimetallic nanoparticles, corresponding to the (111) plane of the PtCu3 bulk alloy. 

The withdrawn hquid-phase samples were analyzed with an HPLC (Biorad Aminex HPX-87C carbohydrate coluttm. 1.2 ttiM CaS04 in deionized water was used as a mobile phase, since calcium ions improve the resolution of lactobionic acid [17]). Dissolved metals were analysed by Direct Current Plasma (DCP). The catalysts were characterized by (nitrogen adsorption BET, XPS surface analysis, SEM-EDXA, hydrogen TPD and particle size analysis). 

Principles and Characteristics A direct-current plasma (DCP) jet is a flowing, gas-stabilised electrical discharge that is maintained by a core consisting of a... 

DCP-AES Direct-current plasma atomic emission spectrometry... 

In a direct-current plasma source (DCP) initial heating of an inert gas, usually argon, is produced by a dc-arc. Experimentally it is arranged for the plasma to be established in a high-velocity gas stream. When the edges of the plasma are cooled with an inert gas vortex, the cooler outer parts have... 

Solutions and precipitates were analyzed on a Beckman Spectra-Span VI direct current plasma emission spectrophotometer (DCP), Precision for the Ca2 + analyses was 3% and for the Ba2 + 2% except for the most dilute samples In which It rose as high as 5%. Calcite mineralogy was determined on a Philips x-ray diffractometer calcite was the only phase recorded except In speed runs of under one hour In duration (not Included In this study) which produced vaterite. Details of analytic procedures are available In Pingitore and Eastman (30,31). 

For the routine determination of analytes in the quality control of the production of speciality chemicals, a combination of direct current plasma emission spectroscopy (DCP-OES) with flow injection analysis (FIA) has been used. Results obtained for the determination of boron, copper, molybdenum, tungsten and zinc in non-aqueous solutions have been published by Brennan and Svehla [3], The principle has been extended to other analytes, carrier liquids, and solvents, and the details of a fully automatic system have been described by Brennan et al. [4]. 

Determination of markers in digesta and feces by direct current plasma emission spectroscopy. Journal of Dairy Science 75, 2176-2183. 

Schematic diagram of the three-electrode direct current plasma.

Direct current plasma (DCP) this is produced by a dc discharge between electrodes. DCPs allow the analysis of solutions. Experiments have shown that although excitation temperatures can reach 6000 K, sample volatilisation is not complete because residence times in the plasma are relatively short (this can be troublesome with samples containing materials that are difficult to volatilise). A major drawback is the contamination introduced by the electrodes. 

J. A. McGuire and E. H. Piepmeier, The characterisation and simplex optimisation of a variable-diameter, multi-electrode, direct current plasma for atomic emission spectroscopy. Can. J. Appl. Spectrosc., 36(6), 1991, 127-139. 

GFAAS = graphite furnace (flameless) atomic absorption spectroscopy MCAAS = micro-cup atomic spectroscopy DCOP-AES = direct current plasma-atomic emission spectroscopy HFP-AES = high frequency piasma-torch-atomic emission spectroscopy NAA - neutron activation analyst-, atomic absorption spectroscopy AAS - atomic absorption spectrophotometer XES = X-ray energy spectrometry and SEM - scanning electron microscopy. 

There are two popular types of plasma sources l) the direct current plasma (DCP), and 2) the inductively coupled plasma (ICP). In the commercial version of the former plasma source (marketed by Spectrometries, Inc.), the sample is aspirated with argon through a small orifice into a chamber where the large droplets settle out and the fine mist is conveyed by the argon stream through a chimney to the vertex of a plasma which is in the form of... 

Because of the disadvantages of the ICP systems listed above, we chose to do our study on the simpler less expensive sequential direct current plasma system (27, 59-65) It is well to recognize that in any choice of this kind trade-offs may become necessary. For example, the DC plasma is subject to more or less severe matrix effects, and these must be accounted for in setting up the methodology (28 ). These effects are illustrated in Figures 1 and 2 which show the influence of the large potassium concentrations on both the atom and ion lines of barium. 

Emission Spectrometry DCPAES = Direct Current Plasma Emission Spectrometry FAFS = Flame Atomic Fluorescence Spectrometry FAAS = Flame Atomic Absorption Spectrometry. 

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