Extractability testing separations

Co (I I) complex formation is the essential part of copper wet analysis. The latter involves several chemical unit operations. In a concrete example, eight such operations were combined - two-phase formation, mixing, chelating reaction, solvent extraction, phase separation, three-phase formation, decomposition of co-existing metal chelates and removal of these chelates and reagents [28]. Accordingly, Co (I I) complex formation serves as a test reaction to perform multiple unit operations on one chip, i.e. as a chemical investigation to validate the Lab-on-a-Chip concept. 

Crops with high acid content have to be tested separately, to demonstrate the robustness of methods with regard to changes in pH. In such cases, where extractions are performed at pH values which are lower than those of acidic crops (e.g., <3), the influence of sample acidity is not significant. It is assumed that under such circumstances an expert statement should be sufficient and may replace validation experiments with representative commodities of this matrix group. 

Extraction and Separation of Alkaloids - The air-dried ground heart-wood (2.2 kg) was extracted by percolation at room temperature with alcohol USP until a negative alkaloid test of the percolate was observed. Removal of the solvent at reduced pressure and at 40° left 71 g of residue that exhibited antimicrobial activity. A 35 g sample of the alcohol-soluble residue was partitioned between 125 ml each of ether and 2Z citric acid In water. The ether layer was extracted twice more with 125 ml of 2% citric acid, filtered to remove some lnterfaclal solids (5.8 g alkaloid negative, no antimicrobial activity), dried (sodium sulfate), and evaporated to dryness, giving 8.6 g of ether solubles that had no antimicrobial activity. 

The second example described here is dormant seeds from Rosa canina. Extracts of these seeds also inhibit germination of seeds of several plants (10). In Figure 5 a scheme is given for extraction and separation oF"three different inhibitor compounds. All these are present in the acid fraction. The first essential step is chromatography on Sephadex LH-20, which separates inhibitor I from inhibitor II and III. Inhibitor I was identified as abscisic acid. The other two inhibitors were separated by methylation with diazomethane, fractional distillation, and column chromatography. The second inhibitor is the a-pyrone 1 . Reaction with diazomethane transforms it into the bi-cyclic compound 19. This bicyclic compound is even more active than the parent a-pyrone 1 . Since we sought structural requirements for bioactivity here also,we tested several synthetic a-pyrones ( 0 - 22) for bioactivity. These compounds had no inhibitory activity. We alio tested the cyclopropane derivatives 23 and 24 In Table II, the bioactivity of the bicyclic compound T9 and two such derivatives is compared. The presence of several carboxylic acid groups seems to be essential (or at least helpful) for bioactivity in this case also. 

The value of recovery data is strongly dependent on the point in the analysis at which the samples were spiked. An extract that is spiked just prior to injection into the HPLC would be expected to give very favorable recoveries, since the only variability being tested is that of the HPLC separation and detection. In contrast, a sample that is spiked at the beginning of the extraction should provide an indication of the loss or degradation occurring throughout the entire extraction, HPLC separation, and quantitation. 

Zhu, Y., Chen, J., Jiao, R. 1997. Hot test and process parameter calculation of purified CYANEX 301 extraction for separating Am and fission products. Global 1997 International Conference on Future Nuclear Systems, October, Yokohama, Japan. 

The enzyme DGAT has not been purified to date, probably because it is a hydrophobic and integral membrane protein. Therefore, DGAT activity was measured using rat liver microsomes as an enzyme source and radiolabeled palmitate as a substrate by the method of Mayorek and Bar-Tana [52] with some modifications [53], The reaction mixture contains microsomal protein, BSA, [14C]palmi-toyl-CoA, MgCl2, diisopropyl fluorophosphate, 1,2-dioleoyl-vw-glyccrol, and a test sample in a total volume of 0.2 ml. After a 15-min incubation at 23°C, lipids are extracted and separated by thin-layer chromatography (TLC). The distribution of radioactivity on TLC is analyzed with a radioscanner to determine the amount of [14C]TG. 

To investigate the specificity of DGAT inhibitors, synthesis of lipids including TG, phosphatidylcholine (PC), and phosphatidylethanolamine (PE) was measured in an intact cell assay using Raji cells by our established method [54], Raji cells are incubated in the presence of [14C]oleic acid with or without a test sample in a total volume of 0.2 ml. After a 20-min incubation at 37°C, [14C]oleic acid is incorporated mainly into PC, PE, and TG, which are extracted and separated by TLC. The distribution of radioactivity in these lipids on TLC is analyzed. 

Except for extraction, no separation methods have been used in the NMR sample preparations in the interlaboratory comparison tests (7 15). Thus, the chemicals of interest, impurities, and background present in the original sample and in the extract were all present in the NMR sample. The advantage of this... 

Samples first were washed in water with manual agitation in a Buchner funnel and then were successively rinsed with methanol, chloroform, methanol, and water. During this process, particulate debris separated from the fibers, and it was assumed that loosely attached water-, methanol-, and chloroform-soluble impurities largely washed out with the filtrate. Preliminary extraction tests for the presence of synthetic dyes were conducted as follows Samples were first boiled in water. If the solution colored, the water extract was analyzed with HPLC, and the sample was then boiled in dilute ammonia. If the ammonia extracts were strongly colored (natural dyes with the exception of very few do not extract into water or dilute ammonia), they were shaken with zinc dust, and if the ammonia extract reduced to a completely colorless solution, it was concluded that the sample was an azo dye (I). Early synthetic dyes often bleed into boiling water, and azo groups will reduce in the presence of zinc dust. 

TABLE III Percent separation yields obtained from HDEHP batch extraction tests on simulated and fully active HAW solutions... 

Process", is able to attain a well satisfactory separation of trivalent actinides from RE. Hot cell extraction tests are in progress. 

Shake for 1 minute, allow the layers to separate, and filter the chloroform extracts through separate filters of about 2 g of anhydrous granular sodium sulfate supported on pledgets of glass wool. Extract each aqueous layer with two additional 10 mL portions of chloroform, filtering and combining with the respective main extracts. Evaporate the chloroform solutions under reduced pressure to dryness, and dissolve each residue in 10 mL of carbon disulfide. The infrared absorption spectrum, determined in a 1-mm cell, of the solution obtained from the test specimen exhibits maxima only at the same wavelengths as that of the solution obtained from the Reference Standard (RS). 

The second point is to always run tests on representative samples. Table IV illustrates this point. Original thermal stability tests were run on an alpha-oximino ester intermediate product that had been isolated by adding water to the reaction mixture, extracting the oil layer that forms with methylene chloride, and removing the methylene chloride by vacuum distillation (labelled pure oil). Later in process development it was decided to eliminate the methylene chloride extraction and separate the oil from the water layer (labelled crude oil) If repeat safety tests had not been run, the thermal stability hazard of this compound might never have been realized, and the compound might have been improperly stored or handled at too high a temperature. 

A more quantitative technique is based on the fact that in a blend containing polyisoprene (or polybutadiene) the rubber phase can be selectively crosslinked by y-radiation (15). The blend was irradiated at 40-68 Mrad under nitrogen so that PI was quantitatively crosslinked. The insoluble fraction was then isolated by benzene extraction. Tests of binary blends of PS and PI homopolymers demonstrated that PI and PS can be well separated after irradiation, and that there is practically no solubility of one homopolymer in the other. This technique can be applied only if PS is the continuous phase. 

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