Separation trace

In principle, all these capabilities will enhance the performance of any type of atomic spectrometry, independently of the nature of the spectroscopic technique used (e.g. a procedure that separates trace elements from a large volume of a highly saline medium and releases them into a smaller volume of dilute nitric acid can be used in conjunction with any type of spectrometer). 

A combined anion exchange-solvent extraction procedure for separating trace amounts of Sm, Eu, Gd, Dy and Er from ThF4 resulted [82]... 

Every coupling application favors one part of the coupling system. A dominating chromatography part leads to the speciation analysis [5,6,26,27]. The elemental specific detection facilities of atomic spectrometry are strongly favored over the multielement capabilities. An inversion of this construction leads to multielement trace analysis in complex matrices with the use of chromatographic equipment as powerful preconcentration and matrix elimination tool [13k The ability of chromatography for a further time resolution between the separated traces is not really required because of the excellent elemental specific detection capabilities of atomic spectrometry. 

Chromatographic purification of the reaction mixture must be effected as soon as possible after workup in order to separate traces of contaminating... 

Hx (heat in) required HI gas catalytic decomposition Hx (heat in) required H2O wash to separate trace HI... 

The purge gas is water scrubbed at 135 -145 bar, reducing the ammonia concentration to less than 200 ppm. The scrubbed purge gas is heated to 35 °C and sent directly to the Prism separators. Trace concentrations of ammonia and water vapor in the gas stream pose no problem to the membrane. Therefore, a dryer system is not required. 

Chang X, Luo X, Zhan G, et al. 1990. Performance for PAN-3 Chelate fiber for adsorbing and separating trace uranium. Mikrochim Acta 101-105. 

Our results indicate that single-stage supercritical extraction processes are limited in their ability to separate trace components from complex mixtures even with the use of co-solvents. However, two-stage processes such as the ones developed here can significantly improve the degree of separation. Utilization of the multicomponent temperature-solubility cross-over region is a promising isolation technique. However, when the substrate contains a wide variety of components, multiple separations may be necessary to complete the isolation and the yields may be low. 

The sucessful experiments for the retention of plutonium onto alumina from TTN0 -HF solution gave enough confidence to recomend the proposed method to separate traces of plutonium from waste solutions in the presence of macroamounts of uranium (VI). Of course, only macroamounts of thorium, uranium (IV) and rare earths are serious interfering ions, since they precipitate with HF. The behavior expected for neptunium in the same system should be similar to plutonium, thorium and rare earths. The retention of neptunium from HNO - HF solutions is in progress. The sorption yield for Pu was around 95%. The sorption mechanism is not well established. Figure 3 shows the proposed flowsheet for recovery of Pu traces from reprocessing waste solutions. 

Diphenyl-2(l//)-pyrazinone (56, R = H) gave l-ethyl-5,6-diphenyl-2(l//)-pyrazinone (56, R = Et) and a separable trace of the ethoxy isomer (Et2SO4, MeONa, MeOH, 20°C reflux, 1 h %) homologues likewise. ... 

Extraction of bismuth with dithizone in CHCI3 or CCI4, in the presence of masking agents, is a selective method for separating traces of Bi. It is often connected with the determination of Bi as dithizonate (see below). 

A solid chelating material, l-nitroso-2-naphthol supported on silica gel, provides a rapid and highly selective mean of separating traces of Co(II) from natural waters [19]. Open-cell polyurethane foam loaded with PAN azo reagent [20], and organic resins modified with nitroso-R salt have been used similarly [21,22]. 

Precipitation of titanium as the hydroxide Ti(OH)4 with an excess of NaOH solution enables the separation of Ti from V(V), Cr(VI), Mo(VI), W(VI), P(V), and A1 [1,2]. Double precipitation gives the best separation. Traces of Ti are separated in the presence of Fe, Al, Mn, Mg, or La as collector. Precipitation of Ti with ammonia in the presence of EDTA separates this metal from Fe, Mn, Al, and other metals. 

To be able to separate trace compounds, the stability of the compounds formed between the analyte and stationary phase must have the following properties (1) they must be relatively high but low enough to be drawn by the mobile phase (2) the differences between the stability of the compounds must be large enough to allow separation of the analytes. 

A limitation of the above simple and effective method of separating trace components from the main component is the impossibility of using it for the analysis of trace components with the same chemical nature and reactivity as the main substance. 

With the aid of the carrier gas flow the trace zone was transferred into the analytical column. Under such conditions carbon dioxide is completely retained by diethanolamine. The concentration and analysis were performed at room temperature. The separated trace components were sensed by a flame-ionization detector. The carrier gas (nitrogen) flow-rate was 60 ml/min. For regeneration the concentration column was heated in the carrier gas flow at 100—105°C for 5—7 min. For heating and cooling a special device forming part of a KhT-2M chromatograph manufactured in the U.S.S.R. was used. The duration of the total analytical cycle was 25 min. This method permits the determination of hydrocarbon gases in carbon dioxide at concentrations down to 10" %. 

Chang X., Zhan G., Luo X., Su Z. Synthesis and efficiency of polyjacrylamidrazone-hydrazide) chelating fibre for preconcentrating and separating trace gold and palladium from solution. Microchimica Acta 1994 12 245-251. 

A composite 3D reconstruction is generated from combined or separated trace slots and can be rotated and viewed at any angle see Fig. 6). The 3D reconstruction can also be saved and viewed as a QuickTime movie. 

I. The user can take advantage of trace slots (16, 25) to outline and quantify different intensity levels of a given label. For the cell reconstructed and viewed at different angles in Fig. 9, actin is labeled with the ABD-GFP fusion protein probe (26). In this figure, the cell body, represented as a transparent faceted reconstruction, is outlined in trace slot I while intensely labeled actin, seen in anterior and lateral pseudopods, is in a separate trace slot. A lower intensity of labeled actin, automatically outlined in trace slot 3, can be seen to localize primarily to the uropod. 

Column chromatographic systems can also be used to separate trace metals by complexation methods. Knapp et al. (325) used diethyldithiocarbamate solution on a Chromosorb W-DMCS column to concentrate metals and either eluted them in bulk for x-ray analysis or sequentially for atomic absorption analysis. Acetylacetonates have also been used for column separations (326). 

Precipitation of Ag as chloride, or better as bromide, with a slight excess of precipitant may be a useful method of separation. Traces of Ag have been separated by thallium iodide as the collector. The precipitation can be dissolved in diluted H2SO4-H2O2 solution. A widely applicable method for the isolation of traces of Ag consists in co-precipitation with elemental tellurium formed by adding tin(II) chloride to 2 mol 1 HCl solution of the sample containing Te(IV) (see above). The extraction constant of primary Ag dithizonate is such that Ag can be extracted quantitatively from 6 mol 1 H solution by the use of 0.001%(w/v) dithizone solution in carbon tetrachloride. Anions such as halides and thiocyanates that form slightly soluble or complex Ag salts must be absent when extraction is made in mineral acid medium. Other metals extracted at high acidity are Pd, Au, and Hg. Copper will also be extracted. 

Figure 5 Effect of chronic hypoxia on the sensitivity of chemoreceptor nerve discharge to specific ETA-receptor antagonist, BQ-123. Left panel shows three superimposed traces of integrated carotid sinus nerve activity in normal rat carotid body separate trace indicates changes in hath PO2. Basal and hypoxia-stimulated nerve activity are minimally altered in the presence of 5pM BQ-123. After 3 days of chronic hypoxia (380torr right panel), nerve activity evoked by acute h5 poxia is substantially reduced in the presence of the drug. (From Ref 9.)...

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