Carbon, activated analysis

The IR spectra in Fig.7 indicate the preferential adsorption of NO on the Co sites. It may be conjectured that the Mo sulfide species are physically covered by the Co sulfide species or that Co-Mo mixed sulfide species are formed and the chemical natures of the Co and Mo sulfides are mutually modified. The Mo K-edge EXAFS spectra were measured to examine the formation of mixed sulfide species between Co and Mo sulfides. The Fourier transforms are presented in Fig.8 for MoSx/NaY and CoSx-MoSx/NaY. The structural parameters derived from EXAFS analysis are summarized in Table 1. The structure and dispersion of the Mo sulfides in MoSx/NaY are discussed above. With the Co-Mo binary sulfide catalyst, the Mo-Co bondings are clearly observed at 0.283 nm in addition to the Mo-S and Mo-Mo bondings. The Mo-Co distance is close to that reported by Bouwens et al. [7] for a CoMoS phase supported on activated carbon. Detailed analysis of the EXAFS results for CoSx-MoSx/NaY will be presented elsewhere. It is concluded that the Co-Mo mixed sulfides possessing Co-S-Mo chemical bondings are formed in CoSx-MoSx/NaY. 

To date, a few methods have been proposed for direct determination of trace iodide in seawater. The first involved the use of neutron activation analysis (NAA) [86], where iodide in seawater was concentrated by strongly basic anion-exchange column, eluted by sodium nitrate, and precipitated as palladium iodide. The second involved the use of automated electrochemical procedures [90] iodide was electrochemically oxidised to iodine and was concentrated on a carbon wool electrode. After removal of interference ions, the iodine was eluted with ascorbic acid and was determined by a polished Ag3SI electrode. The third method involved the use of cathodic stripping square wave voltammetry [92] (See Sect. 2.16.3). Iodine reacts with mercury in a one-electron process, and the sensitivity is increased remarkably by the addition of Triton X. The three methods have detection limits of 0.7 (250 ml seawater), 0.1 (50 ml), and 0.02 pg/l (10 ml), respectively, and could be applied to almost all the samples. However, NAA is not generally employed. The second electrochemical method uses an automated system but is a special apparatus just for determination of iodide. The first and third methods are time-consuming. 

Other techniques that have been used include subtractive differential pulse voltammetry at twin gold electrodes [492], anodic stripping voltammetry using glassy-carbon electrodes [495,496], X-ray fluorescence analysis [493], and neutron activation analysis [494],... 

In this body of catalysts, the metal cluster is said to be formed around the carbonyl precursor. According to SEM and TEM imaging, it appears that the carbonyl clusters are on the order of 1 pm in diameter when supported on carbon.192 Analysis with FTIR has shown that the carbonyl is present.189 190 198-200 203 Non-noble metals have also been studied along side the noble-metals in this group of catalysts. Table 4 lists the non-noble metal carbonyl catalysts studied.189-192 198-200 The non-noble metal carbonyl catalysts studied produced mixed results for the ORR activity. 

It is seen by examination of Table 1.11(b) that a wide variety of techniques have been employed including spectrophotometry (four determinants), combustion and wet digestion methods and inductively coupled plasma atomic emission spectrometry (three determinants each), atomic absorption spectrometry, potentiometric methods, molecular absorption spectrometry and gas chromatography (two determinants each), and flow-injection analysis and neutron activation analysis (one determinant each). Between them these techniques are capable of determining boron, halogens, total and particulate carbon, nitrogen, phosphorus, sulphur, silicon, selenium, arsenic antimony and bismuth in soils. 

A method has been developed for the determination of technetium-99 in mixed fission products by neutron activation analysis Tc is separated from most fission products by a cyclohexanone extraction from carbonate solution, the stripping into water by addition of CCI4 to the cylohexanone phase, and the adsorption on an anion exchange column. Induced Tc radioactivity is determined using X-ray spectrometry to measure the 540 and 591 keV lines. The sensitivity of the analysis under these conditions is approximately 5 ng. The method has been successfully applied to reactor fuel solutions. 

Fruchier rial. (1980), determined by X-ray fluorescence IXRF), except Aland Naby ncuiran activation analysis (NA At. Mg by flame atomic absorption tlidnum borate fusion (FAA), and B by plasma emission spectroscopy (sodium carbonate fusion) (PE5) Saether (1980), determined by XRF after low-temperature ashing (LTA) of raw oil shale samples In = 10). 

NAA NAAQS NBO NCP Neutron activation analysis National ambient air quality standards Non-bridging oxygen Non-carbonate portion... 

Quantitative trace element analysis of diamond by LA-ICP-MS using different synthetic multielement carbon based standards (e.g., cellulose pellets) is discussed by Rege et al 2, whereby 13C was used for internal standardization. Concentrations of 41 elements were determined in two fibrous diamonds from Jwaneng Botswana (JWA 110 and 115) by relative sensitivity coefficients measured using the synthetic cellulose standard. The analytical data were verified by means of instrumental neutron activation analysis (INAA) and proton induced X-ray emission (PIXE).72... 

Troth (32) has studied the polymerization of vinyl acetate in the presence of triphenylmethane and observed the effects discussed above. In practice, there are complications resulting from reactions involving the initiator radicals and the transfer agent. These complications were found also when carbon tetrabromide was used as a transfer agent in the polymerization of styrene in this case, the bromine contents of the polymers were determined by neutron activation analysis (17). 

Activated carbon Activated carbon will remove a broad-spectrum of chemicals (e.g., organics, metal) from solution. Although nonselectivity of activated carbon is a limitation (and toxicants cannot typically be recovered) it can be useful in cases where toxicity is not removed by any of the other Phase I treatments, or when combined with chemical analysis before and after treatment. Samples are passed through a column (or mixed as a slurry) containing carbon and then tested for toxicity. 

It is obvious, therefore, that 14 MeV neutron activation analysis can not compete with thermal neutron activation analysis as a technique for trace element analysis. In simple matrices, however, the rapid and non-destructive nature of the technique recommends its use for routine analysis of large numbers of samples for elemental abundances at the one milligram level, or above. It is unfortunate that the element carbon can not be determined by this technique. The nuclear reaction 12C(n, 2n)1 C which would be of great analytical importance is endoergic to the extent of nearly 19 MeV. This reaction is obviously not energetically possible using the 14.7 MeV neutrons produced by the 2H(3H,w)4He reaction commonly employed in most neutron generators. 

Debrun, J. L., J. N. Barrandon, and P. Albert Contribution to Activation Analysis by Charged Particles Determination of Carbon and Oxygen in Pure Metals, Possibilities of Sulphur Determination. The 1968 International Con-... 

Nazaki, T N. Yatsurugi, N. Akiyana, and I. Imai Charged Particle Activation Analysis for Carbon, Nitrogen and Oxygen in Semiconductor Silicon. The 1968 International Conference Modem Trends in Activation Analysis, Gaithersburg, Maryland, October 7—11, 1968, Paper 8. 

The fact that neutron irradiation of hydrogen and carbon produces no significant radioactivity makes Neutron Activation Analysis (NAA) a very sensitive analytical technique for detecting impurities in polymer cable insulation and has been extensively used for this purpose. It is therefore of some interest to compare PIXE with NAA. 

The catalytic system 11/MAO shows lower activity in propylene polymerization as compared to polymerization of ethylene, with a similar trend in the relationship between the polypropylene yield and Al Zr ratio (compare entries 1,2 7, and 8). The proton and carbon spectroscopic analysis of the polypropylene obtained revealed only vinyl/isopropyl end groups. The fact that... 

NOTE All values are given as weight percent ( 95% confidence limit). Sulfate and chloride were analyzed by ion chromatography carbonate was analyzed by classical titration and calcium, magnesium, chlorine, aluminum, and sodium were analyzed by neutron activation analysis. 

Similarly, there is a great potential in the use of water vapour for the analysis of the porous texture, because it has considerable potential due to both the easy experimental conditions (at room temperature the whole range of relative pressures can be covered) and the characteristics of the molecule itself (polar molecule and small kinetic diameter-0.28 nm). This vapour is widely used in the characterisation of inorganic porous solids, such as zeolites, silicas, and clays. However, its interaction with carbon materials (microporous carbons coals, activated carbon fibres, carbon molecular sieves and porous carbons activated carbons), is more complex than the interaction of non-polar molecules [8]. 

It has been stated that the bulk of the published work on activation analysis has been concerned with the more general technique of neutron activation. A low probability of neutron activation or an overlong or overshort half-life of the activated species produced can, however, result in poor sensitivity for the method. This is the case with a number of the lighter elements such as beryllium, aluminum, carbon, nitrogen, and oiQTgen. In a number of these cases a satisfactory alternative may be found in activation by charged-particle bombardment (65). 

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