Maximum concentration extraction

When testing BW, the sample should represent the maximum concentration of dissolved and suspended solids in the boiler. The most suitable point for taking the sample is the continuous BD line. (Continuous BD lines are specifically designed and located to extract BW from the point of highest solids concentration in the boiler.)... 

Solvent extraction can be automated in continuous-flow analysis. For both conventional AutoAnalyzer and flow-injection techniques, analytical methods have been devised incorporating a solvent extraction step. In these methods, a peristaltic pump dehvers the hquid streams, and these are mixed in a mixing coil, often filled with glass ballotini the phases are subsequently separated in a simple separator which allows the aqueous and organic phases to stratify. One or both of these phases can then be resampled into the analyser manifold for further reaction and/or measurement. The sample-to-extractant ratio can be varied within the limits normally applying to such operations, but the maximum concentration factor consistent with good operation is normally about 3 1. 

The use of a volatile solvent, e.g., pentane, was not explored because of inherent limitations. Concentration of such extracts was not possible because of the volatility of the sample components. Therefore the maximum concentration factor that could have been achieved was limited by the partition coefficients of the compounds into the solvent used in the extraction. For most compounds this factor was estimated to be about 10 1. Furthermore, with CRMS and other general detectors, the solvent masking problem would still preclude observation of many compounds. Therefore, the method would be limited to detectors that are not responsive to the solvent used in the extraction. Recent work (3.4,5) has indicated that extraction with a volatile solvent is a viable approach for the analysis of a small set of compounds, e.g., the trihalomethanes, with an electron capture detector in drinking water samples where concentration factors of 10 1 or less are acceptable. 

Rectal bioavailability and pharmacokinetics. Serenoa repens extract, administered rectally to 12 healthy male volunteers at a dose of 640 mg/person, produced the mean maximum concentration in plasma of nearly 2.60 (Xg/mL approx 3 hours after administration, with mean value for the area under the curve AUC 10 (Xg/hour/mL. The bioavailability and pharmacokinetic profile were similar to those observed after oral administration. T j occurred approx 1 hour later, and plasma concentration 8 hours after drug administration was still quantified. The drug tolerability was good, and no adverse effect was observed ". Serenoa repens capsules, administered orally at a dose of 160 mg four times daily or rectally 640 mg daily for 30 days to 60 patients with BPH, produced no significant differences in diminu-... 

The maximum concentration of cholesterol retracted occurred after the passage of 2.5 kg of CO2 at 138 bar/S0°C This was 2.5 times the amount extracted at 345 bar/50°C and approximately 2.3 times the amount extracted at 241 bar/150°C. Extraction at lower pressures increased the solubility of cholesterol but decreased the weight of total lipid extracted per unit weight of CO2 used. Most of the cholesterol was removed after extracting with 20 kg CO2 at 138 bar/40°C where only 22% of the total lipid had been removed. 

Sedan crater as determined by Hansen (4) is quite uniform to the depth of explosive emplacement or over 300 feet. The maximum concentrations of tritium in soil water observed on the crater lip at 4 to 5 feet in our samples are in the same range as those reported by Hansen (4) in crater fallback. Figure 7 shows the vertical distribution of tritium in soil water extracted from Sedan crater fallback, according to Hansen (4), and the maximum concentrations found at our four crater lip sites. 

The uranium and thorium ore concentrates received by fuel fabrication plants still contain a variety of impurities, some of which may be quite effective neutron absorbers. Such impurities must be almost completely removed if they are not seriously to impair reactor performance. The thermal neutron capture cross sections of the more important contaminants, along with some typical maximum concentrations acceptable for fuel fabrication, are given in Table 9. The removal of these unwanted elements may be effected either by precipitation and fractional crystallization methods, or by solvent extraction. The former methods have been historically important but have now been superseded by solvent extraction with TBP. The thorium or uranium salts so produced are then of sufficient purity to be accepted for fuel preparation or uranium enrichment. Solvent extraction by TBP also forms the basis of the Purex process for separating uranium and plutonium, and the Thorex process for separating uranium and thorium, in irradiated fuels. These processes and the principles of solvent extraction are described in more detail in Section 65.2.4, but the chemistry of U022+ and Th4+ extraction by TBP is considered here. 

In Figure 7, we present the w/w concentration of acetone in the supercritical phase on a C02-free basis versus the corresponding concentration of acetone in the liquid phase. The curve shows a broad maximum at a range of concentrations of acetone in the aqueous phase between 2% and 15% w/w. The maximum concentration of acetone in the supercritical phase is close to 95% w/w. We can, therefore, obtain almost pure acetone from a dilute aqueous solution using a single-step extraction with supercritical carbon dioxide. 

Partition the concentrated extract against 40 mL of concentrated sulfuric acid. Shake for two minutes. Remove and discard the acid layer (bottom). Repeat the acid washing until no color is visible in the acid layer (Perform acid washings a maximum of four times). 

Figures 5 and 6 show how the water extractable chloride and bromide change with storage at 175 C and 200 C for a 1983 and a 1985 vintage flame retarded novolac epoxy. In both of these figures, the chloride, most of which comes from the ECN, changes from an initial concentration of <10 ppm to a maximum concentration of 17 ppm after 1000 hours at 175 C and 23 ppm after 1000 hours at 200 C. The amount of chloride extracted from both epoxies is similar. The water extractable bromide, however, increases for the 1983 epoxy after an induction period of about 168 hours. The bromide from the 1985 epoxy also increases, but at a much slower rate. These results show that the thermal stability problems of the brominated organic can be minimized, provided the flame retardant system is carefully selected.

Maximum concentration enrichment possible is limited by the partition coefficient (Equation 12.11), whereas in SLM it is dependent on the degree of trapping (Equation 12.2), which can be influenced by controUing the pH of the different phases. Therefore, SLM provides more degrees of freedom by which the conditions of extraction can be tuned. 

Amorphous aluminum oxide has recently been proved to extract lithium from brines and bitterns having lithium concentrations of 0.83 and 13.1 mg/1, respectively. The sorption may be explained by the formation of hydrous lithium aluminum oxide. The sorption capacity of amorphous hydrous aluminum oxide was found to be 4.0 mmol/g. For brines and bitterns the lithium concentration factors on the sorbent attained values of 370 and 130, respectively equilibrium was reached after 7 days. The desorption of lithium ions was carried out with boiling water yielding a maximum concentration factor of lithium in the eluate of 46 in reference to the initial lithium concentration of the brines. Lithium was separated from the eluates by solvent extraction with cyclohexane containing thenoyltrifluoracetone and trioctyl-phosphine oxide, subsequent back extraction with hydrochloric acid, and precipitation of lithium phosphate by addition of K3P04. The purity of the precipitate amounted to at least 95% I7 21). 

The degree of the metal extractions depends on its concentration. Por example, with increasing europium concentration the distribution coefficients in the alkali-DOBTA system decrease, while in the alkali-tartaric acid system a maximum at 7x10 4 M Eu concentration is observed. As we suggested the enhancement in the metal distribution coefficient is evidently due to the metal polymerization in the organic phase, and the decrease is caused by polymerization in the aqueous phase, which eventually results in low extractable polymer form. The latter assumption is supported by the fact that as the alkali concentration increases the maximum on extraction curves undergoes a shift towards lower concentration of the metal. 

I. Loading capacity. This property refers to the maximum concentration of solute the extract phase can hold before two liquid phases can no longer coexist or solute precipitates as a separate phase. 

Even though the amount of silica extracted seemed to be limited by the room temperature solubility limit, this limit was raised by increasing either the alkali concentration or the ratio of alkali to quartz. Thus by increasing the sodium carbonate concentration from 1.0 M to 2.0 M, the maximum amount extracted was raised from 70% to 98.5%. Moreover, when the quantity of quartz leached for 1 hr. with a 1.0 M solution at 250 C was reduced from 2 g. to 1 g., the percentage extracted increased from 58% to 95%. 

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