Extraction performance

Extractions performed with the conveyor stopped allow more assured accuracy by the certainty of including fines in the sample increment. Sampler design to extract increments from a flat belt or rotaiw table sampler while the conveyor is stopped minimizes potential for residual fine particles remaining on the conveyor surface in carrying out extractions. See Fig. 19-6 for rotary table sampler extraction diagram. 

Thorium is a highly insoluble element, mainly carried in the particulate form in river waters. This is well shown by Th data for the MacKenzie river (Vigier et al. 2001) and for the Kalix river (Andersson et al. 1995 Porcelli et al. 2001) in both cases, more than 95% of Th is carried by >0.45 pm particles. An important part of this Th is included within detrital material. This is illustrated by sequential extractions performed on sediments from the Witham river (Plater et al. 1992), which show the very low amount of Th in ion-exchangeable and organic-bound fractions compared to Th in Fe-Mn oxides... 

PFE is based on the adjustment of known extraction conditions of traditional solvent extraction to higher temperatures and pressures. The main reasons for enhanced extraction performance at elevated temperature and pressure are (i) solubility and mass transfer effects and (ii) disruption of surface equilibria [487]. In PFE, a certain minimum pressure is required to maintain the extraction solvent in the liquid state at a temperature above the atmospheric boiling point. High pressure elevates the boiling point of the solvent and also enhances penetration of the solvent into the sample matrix. This accelerates the desorption of analytes from the sample surface and their dissolution into the solvent. The final result is improved extraction efficiency along with short extraction time and low solvent requirements. While pressures well above the values required to keep the extraction solvent from boiling should be used, no influence on the ASE extraction efficiency is noticeable by variations from 100 to 300 bar [122]. 

Table 3.48 Comparison of extraction performance of polymer/additive systems...

The number of reports on on-line TLC analysis of extracts is quite limited. Stahl [16,29] described a device for supercritical extraction with deposition of the fluid extract on to a moving TLC plate. On-line SFE-TLC provides rapid and simple insight into the extraction performance. Its strength is that the extract is deposited on a plate, which means that detection is a static process. Limitations of SFE-TLC are that quantification is difficult, and that the stability of components on the support material or in the presence of oxygen may be a problem. For additives in beverages (such as benzoic... 

Just one extraction performed on a solution of a complicated sample will likely not result in total or at least sufficient separation of the analyte from other interfering solutes. Not only will these other species also be extracted to a certain degree with the analyte, but some of the analyte species will likely be left behind in the original solvent as well. Thus, the analyst will need to perform additional extractions on both the extracting solvent, to remove the other solutes that were extracted with the analyte, and the original solution, to remove additional analyte that was not extracted the first time. One can see that dozens of such extractions may be required to achieve the desired separation. Eventually, however, there would be a separation. The process is called countercurrent distribution. 

Many t)q)es of extraction procedures have been employed for the extraction of ginsenosides from fresh or dry ginseng plant material as well as from ginseng preparations. Characteristic for most of the extraction methods is the use of methanol or ethanol or different aqueous mixtures of these two solvents, which also clearly enhance the extraction performances of these compounds compared with pure methanol or ethanol at room temperature (Anderson and Burney, 1998 Christensen et ah, 2006 Euzzati, 2004 Lou et ah, 2006a). In order to enhance the recovery of... 

Only case (2) can provide a comparison between conventional and micellar extraction. The few comparisons reported in the literature on the metal extraction performance of microemulsions containing an extractant with that of the extractant on its own are, at first sight, contradictory. In some cases microemulsions produce both synergism and extraction rate enhancement with respect to the single surfactant, whereas in others they... 

Control of the liquid gas (L/C) ratio in the towers is critical in maintaining the design extraction performance relatively small changes can result in significant loss of extraction. 

Figure 4 shows the recoveries of the 19 haloethers. Overall, the recoveries were quite good (averaging around 70 percent across the 19 compounds) but the agreement between the duplicate extractions performed in parallel was not as good as in the case of the nitroaromatics, however, it was within 15 percent for most compounds. To determine if the pressure had any effect upon recovery, we compared experiments 5,6 with experiments 9,10 because they were pairs (performed in parallel at different pressures) and they were performed with sand samples spiked under identical conditions. All recoveries were slightly higher when extractions were performed at lower pressures. This seems to be in contradiction with what we obtained for experiments 7,8 however, in this case the sand was spiked directly in the extraction vessel and therefore, the data from experiments 7,8 cannot be compared with the data from experiments 5,6. 

The following basic procedures generally apply to all extractions performed. In cases where the extract did not undergo further analysis, steps related to analyte collection do not apply. 

Dhami et al. of BARC studied another mixed solvent system, 0.2 M CMPO -0.3 M HDEHP in n-paraffin, and a strip solution of 0.4 M hydrazine hydrate-0.4 M formic acid-0.05 M DTPA (371). The extraction performance of the process was also satisfactory. 

Second, as a solvent recycle process, which ran for 54 hours without solvent clean-up to treat 3.85 L of a DIAMEX An(III) + Ln(III) product. This second hot test, which generated 6.5 L of Am(III) + Cm(III) product, revealed partial degradation of t Pr-BTP, probably because of alpha/gamma radiolysis reflected by a 40% decrease in the solvent-extraction performance observed after two cycles (207). 

Courson, O., Lebrun, M., Malmbeck, R., Pagliosa, G., Romer, K., Satmark, B., Glatz, J.P. 2000. Partitioning of minor actinides from HLLW using the DIAMEX process. Part 1 - Demonstration of extraction performances and hydraulic behaviour of the solvent in a continuous process. Radiochimica Acta 88 857-863. 

Some of the modifiers in this study (1-5) were also evaluated in the isoparaffinic diluent Isopar L for cesium extraction performance from a Savannah River waste simulant. The effect the modifiers have on the cesium distribution ratio in aliphatic diluents is more pronounced than it is in polar diluents, such as 1,2-DCE, previously used. The cesium distribution results are shown in Table 4.17 alongside those obtained from 1 M NaN03 in 1,2-DCE. 

Wennrich [167] optimised important accelerated solvent extraction parameters, such as extraction temperature and time, using a spiked wetland soil. The effect of small amounts of organic modifiers on the extraction yields was studied. An extraction temperature of 125 °C and ten-minute extractions performed three times proved optimal. Two accelerated solvent extraction-solid-phase microextraction procedures without and with an organic modifier (5% acetonitrile) were evaluated with respect to precision and detection limits. 

Using this approach for natural products dereplication, data are routinely obtained from 40 gg of crude extract. Performance examples include the identification of 16 analogs of teicoplanin and 12 analogs of phenelfamycin from separate samples. The summary of results obtained for phenelfamycin is shown in Table 6.4. The correlation of fraction, retention time, and molecular weight provides the essential information for rapid dereplication and identification. The time required to dereplicate natural product samples is about 1 week with this LC/MS-based method compared to several weeks by previous methods that involve traditional isolation steps. The use of this LC/MS-based methodology results in greater clarity and confident decisions for proceeding with the full structural study of an active component derived from a culture. 

Solubility diagrams were prepared for the phases that separated in the lemon oil extractions performed in this study with carbon dioxide. Such diagrams can serve only as-guides, since solubility is composition-dependent and is a function of the amount extracted. The data are shown in Figures 4, 5, and 6 at 303, 308, and 313 K, respect vely. 

Semi- or non-volatile chlorinated organic compounds, hexachlorobutadiene, hexachlorocyclopentadiene, octa, chlorocyclopentadiene, hexachlorobenzene Extractions performed on homogeniser using hexane, hexane -benzene or hexane -toluene Purge and trap method, recoveries 88-125% 0.1 PPb [189]... 

One of the challenges facing early, as well as contemporary, chemists is how to extract the pharmacologically active principle (such as an alkaloid) from a plant. This is desirable because it allows identification, assessment of pharmacological effects, constant dosage, and the opportunity to create liquid forms of the extract. For example, soaking plants in alcohol (ethanol) creates a tincture, which was, undoubtedly, one of the first organic extractions performed by man. 

Star anise volatile oils can also be isolated by supercritical C02 extraction coupled to a fractional separation technique. Gas chromatography-mass spectrometry analysis of the various fractions obtained in different extraction and fractionation conditions allowed the identification of the best operating conditions for the isolation of essential oil. A good extraction performance was obtained operating at 90 bar and 50°C (for 630min) for both treated materials. Optimum fractionation was achieved in both cases by operating at 90 bar and -10°C in the first separator and at 15 bar and 10°C in the second (Della Porta eta/., 1998). 

The technique employed almost exclusively in the process developed is extraction chromatography (LLC), which is an ideal technique, in view of the column exchange capacities, for the extraction of moderate amounts of material present in a limited volume, or for the recovery of elements present in low concentration in large volumes. The simplicity of the equipment and the low sensitivity of extraction performance to fluctuations in solution throughputs make it a simpler technique for use than liquid-liquid extraction. Moreover, LLC lends itself well to discontinuous operation. In the case of difficult separations, such as Am/Cm separation, LLC offers the advantage of a large number of stages in a simple, compact unit. Since the extraction of the U(VI) present in the Masurca waste in macroconcentration is not economically feasible by LLC, the conventional liquid-liquid technique was adopted. 

Prasad, R. And K.K. Sirkar Hollow Fiber Solvent Extraction Performances and... 

The extraction performances under different experimental conditions (i.e. varying the pH, the composition of surfactant mixtures, the amount of chelating compound) were also investigated for our test system. The results are shown in Table III. 

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