Enrichment procedure

The enrichment procedure uses the small mass difference between the hexafluorides of uranium-235 and uranium-238 to separate them. The first procedure to be developed converts the uranium into uranium hexafluoride, UFfl, which can be vaporized readily. The different effusion rates of the two isotopic fluorides are then used to separate them. From Graham s law of effusion (rare of effusion l/(molar mass)1/2 Section 4.9), the rates of effusion of 235UFfe (molar mass, 349.0 g-mol ) and 238UF6 (molar mass, 352.1 g-mol ) should be in the ratio... 

Platinum is used therapeutically as ds-platin, carboplatin and iproplatin against tumors (Konig and Schuster 1994). Determination of Pt in serum must be carried out after enrichment procedures followed by GF-AAS. 

Biodegradation not observed during enrichment procedures (Smith et al. 1978)... 

Ironically, our current plans call for the reverse linkage of the above enrichment procedures. That is, we shall use an electromagnetic isotope separator to enrich argon isotopes for a mass spectrometry experiment, and we shall enrich radiocarbon via thermal diffusion for improved mini-gas proportional counting. 

Analytical methods for detection of nickel in biological materials and water include various spectrometric, photometric, chromatographic, polarographic, and voltametric procedures (Sunder-man et al. 1984 WHO 1991). Detection limits for the most sensitive procedures — depending on sample pretreatment, and extraction and enrichment procedures — were 0.7 to 1.0 ng/L in liquids, 0.01 to 0.2 pg/m3 in air, 1 to 100 ng/kg in most biological materials, and 12 pg/kg in hair (WHO 1991 Chau and Kulikovsky-Cordeiro 1995). 

In this procedure the soil sample (spiked with isotopic marker compounds) is processed in a two-part enrichment procedure (Fig. 5.3). In part I, a mixture of the sample and sodium sulphate is subject to solvent extraction, and the extract is, in the same process, passed through a series of silica-based adsorbents and then through the carbon/glass fibre adsorbent. The extract passes through the adsorbents in the following order potassium silicate, silica gel, cesium or potassium silicate, silica gel and finally an activated-carbon... 

Application of 2 fractional factorial design allowed the optimization of the enrichment procedure for the determination of aluminum by AAS. The optimum conditions were found to be 4 of pH, 10 of reagent/metal mole ratio, 15 luL of elution volume and 1 mL min of flow rate. 

P. Kotianova and E. Matisova, Liquid-phase microextraction and its utilization for trace analysis of organic compounds in water matrix. Chemicke Listy, 2000,94(4), 220-225. Liu Jf, Chi Yg, Jiang Gb, C. Tai, Peng Jf and JT. Hu, Ionic liquid-based liquid-phase microextraction, a new sample enrichment procedure for liquid chromatography. Journal of Chromatography A, 2004,1026(1-2), 143-147. 

As the most important inorganic mass spectrometric technique, ICP-MS is also employed for the precise and accurate isotope ratio measurements of a multitude of elements (such as Li, B, S, Fe, Sr, Pb, U, Pu) in environmental samples (see Chapter 8).9,88-90 Isotope ratio measurements of environmental samples require special careful sample preparation techniques including trace/matrix separation and enrichment procedures if the analytes are at the trace and ultratrace level. As an example, the schematic diagrams of the separation and enrichment procedures for the precise isotope analysis of Pu, U and Sr in water samples from the Sea of Galilee using double-focusing... 

Figure 9.17 Schematic diagram of the separation and enrichment procedures for precise isotope analysis of Pu, U and Sr. (L. Halicz, J. 5. Becker et al. Int. J. Mass Spectrom., 249-250, 296 (2006). Reproduced by permission of Elsevier.)...

Protamine sulfate has a low affinity for IgM and is only recommended for producing small amounts of immunoglobulin. Some form of enrichment procedure before chromatography is advised. 

Data enrichment needs access to external information sources that are not necessarily accessible from the system hosting the database or the web server. It needs update privileges on tables that are outside the core event tables. As such, it may need to be distributed, but not necessarily concurrent. In fact, our implementation locks data enrichment processes at the database level, to ensure that two installations of the application will not attempt the same enrichment procedure. Regarding performance, data enrichment can be delayed by data acquisition. 

Liu, J.F., Y.G. Chi, and G.B. Jiang. 2004. Ionic liquid-based liquid-phase microextraction, a new sample enrichment procedure for liquid chromatography. J. Chromatogr. A 1026 143-147. 

There are many similarities to the case of Marie and Pierre Curie, and their experience with the manufacturing of radium, to draw from the successful discovery of rhenium the emphasis on the analytical enrichment procedure, the determination to produce weighable samples, the art of taking patents and mastering the production of the new element and, last but not least, the writing of a monograph on... 

As regards fractionation methodologies for the selective determination of Pb and other metals compounds in wines, Lemos et al. [57] have developed a FIA method for the direct determination of available free Pb(II) and total Pb content in wine samples. Lead (II) was chemically retained on a packed polyurethane foam microcolumn, modified by immobilization of 2-(2-benzothiazolyazo)p-cresol (BTAC) and eluted with 0.1 M HC1. The eluate was determined on-line by FAAS. Total Pb was quantified after sample digestion with HN03 and H202, whereas free Pb was determined by direct sample on-line preconcentration and elution. No effect of ethanol on the enrichment procedures was observed. With a preconcentration factor of 26 an LoD of 1 xg l-1 was reached. Four red and three white wines of different origins were analyzed and the total Pb content varied from 8 to 42 p,g 1 1. 

It is too often assumed that because precolumn sample preparation devices, such as solid-phase extraction cartridges, are simple tools, they require relatively little skill or attention to detail for successful use. Cartridges do, however, require attention to detail for successful operation in sample enrichment procedures. Two of the most important parameters to control and understand are flow-rate effects and recovery (or loadability) effects. 

Isolation of Bacteria and Fungi from Soil Using Enrichment Techniques. Two enrichment procedures were employed to isolate microorganisms from soil a tertiary enrichment, in which organisms were isolated from soil after incubation to log phase in the presence of added metal, and a two-phase enrichment, in which organisms were isolated from the unincubated soil and grown on a number of different C sources in the presence of metals. 

In the tertiary enrichment procedure, soil (Ritzville silt loam) was amended with starch (1.0%), NH N03 (0.5%), and Cd,... 

A two-phase enrichment procedure was utilized to select soil organisms on the basis of ability to metabolize classes of organic compounds in the first phase and on ability to grow in the presence of metals in the second phase. In the first phase, aliquots of a standard mineral base medium (Table I, glucose used only in control) were separately amended with 1) aromatic acids. 

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