Extraction temperature

Dichloroethylene can be used as a low temperature extraction solvent for organic materials such as dyes, perfumes, lacquers, and thermoplastics (13—15). It is also used as a chemical intermediate in the synthesis of other chlorinated solvents and compounds (2). 

Dissolve a known weight (ca 0.5 g) of the steel by any suitable procedure. Treat the acidic sample solution (< 200 /jg Co), containing iron in the iron(II) state, with 10-15 mL of 40 per cent (w/v) sodium citrate solution, dilute to 50-75 mL and adjust the pH to 3-4 (indicator paper) with 2M hydrochloric acid or sodium hydroxide. Cool to room temperature, add 10 mL of 3 per cent (10-volume) hydrogen peroxide and, after 3 minutes, 2mL of the reagent solution. Allow to stand for at least 30 minutes at room temperature. Extract the solution in a separatory funnel by shaking vigorously for 1 minute with 25 mL of chloroform repeat the extraction twice with 10 mL portions of chloroform. Dilute the combined extracts to 50 mL with chloroform and transfer to a clean separatory funnel. Add 20 mL of 2M hydrochloric acid, shake for 1 minute, run the chloroform layer into another separatory funnel, and shake for 1 minute with 20 mL of 2M sodium hydroxide. Determine the absorbance of the clear chloroform phase in a 1 cm cell at 530 nm. 

The extrapolated values together with results of the second calibration method are shown in Table V. With the exception of cabbage, agreement to better than 0.2% was found in the results of the two methods for the various foods. The proper refluxing time, for a rapid determination, was then selected from the data for the high temperature extraction shown in the last four columns in Table V. The required times varied from 5 minutes for onions and carrots to 30 minutes for celery. The shortness of these times as compared with other methods illustrates the potential usefulness of the Fischer method as a rapid control method, even though its accuracy is uncertain. 

Accelerated solvent extraction (ASE) is a technique which attempts to merge the beneficial solvation properties of SFE with traditional organic solvents. Specifically, the sample is placed in an extraction vessel which can withstand high pressures while being maintained at a constant temperature. Extraction is carried out by pumping the extraction solvent through the samples for a limited time. As an example of the use of ASE, Richter and Covino extracted PCBs from a 10-g fish tissue sample with hexane... 

Lopez-Avila and Benedicto combined SEE with ELISA to determine sulfamethazine in powdered milk. Various conditions were tested in order to achieve quantitative extraction of sulfamethazine. Variations in extraction pressure, temperature, extraction period, and the presence of organic modifier resulted in extraction efficiencies of 0-92%. Once optimal extraction conditions had been developed, a commercially available ELISA was utilized to determine sulfamethazine concentrations. The LOD was 2.5 pgkg and satisfactory recoveries were obtained at levels from 5 to 15 pgkg-i. 

A common technique used for polyolefin samples is to dissolve the sample using solvents such as xylene, decalin, toluene and di- or trichlorobenzene heated to temperatures as high as 130-150°C. After the plastic sample has been solvated, the polymeric component is precipitated by cooling and/or by adding a cold nonsolvent such as acetone, methanol or isopropanol. Polypropylene does not completely dissolve in toluene under reflux for 0.5 to 1 h with magnetic stirring (typically, 2g of polymer in 40 mL of toluene), yet the additives may be extracted [603]. In addition to additives, most solvents also extract some low-MW polymer with subsequent contamination of the extract. To overcome this a procedure for obtaining polymer-free additive extracts from PE, PP and PS has been described based on low-temperature extraction with n-hexane at 0°C [100],... 

A (Alternative) Treat 4 g (I) in pyridine with SOCl2 as described elsewhere here to get (II). Treat (II) with 2.3 g triethylamine and 2 g piperedine (or other amine) in 5 ml ether. Stir fifteen hours at room temperature extract with 200 ml water, and after precipitation, wash precipitate with 10% Na carbonate, 3N HCI and dry, evaporate in vacuum the ether solution to get (111). Reduce (111) to (IV) as above or with the NaBH4 method or possibly with hydrogenation. 

Preparation of cotton bract extracts. Figure 1 is a flow chart showing our procedures for preparing the various bract extracts. Dried bracts (frost killed) were hand picked just prior to harvest from cotton fields in the Lubbock, Texas area. These were stored at room temperature. Extracts were freeze-dried and stored at -4°C. For inhalation challenge by our subjects each extract was reconstituted with water or saline, as indicated, at a concentration equivalent to the standard crude extract. This Insured that for challenge purposes components were not concentrated as purification progressed. 

When toluene extractions were carried out at 110°C, it was clear from the mass obtained, that toluene remained in the filtrate. With the higher temperature extractions, remembering that the filtration was also carried out at the higher temperature, the mass of filtrate was accordingly lower, since most of the toluene boiled off from the filtrate. 

The easiest way to 10 goes via the synthesis of KDNM (see Section n.C). Acidification of an aqueous solution of KDNM, which should be buffered with H3PO4 (pH = 6.5), followed by low-temperature extraction with diethyl ether, gives the monomeric emerald-green nitrosolic acid 10 dissolved in the ether phase. Slow removal of the solvent yields the yellowish dimeric form of 10. The acid (10) is only poorly characterized. It is known to slowly decompose into HCN and HNO2 in basic solution (decomposition of the anion DNM), while the free acid (10) rapidly decomposes to give fuhninic acid, HCNO and hyponitrous acid, HON=NOH. It should be noted that both the free acid and its metal DNM salts are highly explosive. 

New examples of the formation of pyrazolo[3,4-r/ [l,2,3]triazoles from 4-aminopyrazoloureas, described above in Section 10.05.9.1.2(vii)), have been described. The recent publication of Maggio and co-workers provides an insight into the mechanism of the reaction. It has been shown that nitrosation of 230 with nitrous acid at 0°C followed by adjustment of the pH to 8 and room temperature extraction furnishes, from amongst a mixture of products, the 5,5-bicycle 231 whilst extraction and work-up at 0°C yielded the 5,7-bicycle 232 as the single reaction product. The latter is the precursor to the pyrazolotriazole which results simply from room temperature solution decomposition involving loss of (m)ethyl isocyanate. The formation of the triazole 231 from the tetrazepinone 232 is rationalized as shown in Scheme 48 <2006ARK120>. 

Switch 00 the furnace and cool the apparatus in a hydrogen stream to room temperature. Extract the boat and put the iron into a jar with a well fitting ground-glass stopper. Test the initial iron oxide and the reduced iron with a magnet. How does iron react with acids and alkalies ... 

In summary, there are four major parameters in SFE that can be modified to obtain good selectivity pressure, temperature, extraction period and choice of modifier. Supercritical fluid extraction is easily automated and can be economically viable if the number of samples is large. 

Rutin extraction from buckwheat was optimally performed using between 50% and 60% ethanol with a 3-hr maceration (Kreft et al., 1999). Repeating the extraction two times was sufficient to extract most of the rutin. Lie et al. (2000) demonstrated the optimization of influencing factors such as extraction temperatures, extraction times, and solvent concentrations in a conventional extraction of dry powdered material of Hypericum perforatum. Applied extraction conditions caused variations to favor different components in the mixture. Higher extraction efficiency was achieved with moderately polar solvents to extract flavonoids such as rutin, isoquercitrin, and quercetin. The optimum extraction conditions for dry Hypericum perforatum leaf powder were determined as 44% to 69% ethanol in acetone with a 5.3- to 5.9-hr maceration at 55°C. 

To access the supercritical fluid state, we must have conditions in excess of the critical temperature and pressure. Given the rating of the autoclave, ammonia would not be suitable because one could not access the supercritical state as a result of the pressure limitation. Methylamine would not be suitable for a room temperature extraction because its Tc is too high. Either methane or tetrafluoromethane would be suitable for this application. 

Traditionally a tincture is an ambient temperature extract that is made with a high alcohol level in the extraction liquid, typically 60-70% or more. The herb/extract ratio is usually 1 part dried herb to 10 parts tincture, although a few tinctures were specified at stronger ratios (i.e. more herb) in the British Pharmaceutical Codex and British Pharmacopoeia. 

L, round-bottomed flask equipped with a magnetic stirrer, reflux condenser, and a 250-mL addition funnel are placed 56.3 g (0.26 mol) of MCPBA (80%) and 350 mL of dichloromethane. The suspension is stirred and a solution of 38.0 g (0.16 mol) of 9-n-butyl-1,2,3,4,5,6,7,8-octahydroacridine in 120 mLof dichloromethane is added rapidly (exotherm). When the reaction mixture ceases to boil gently from the heat of reaction, it is heated to extend the reflux period to a total of 2.5 hr. The reaction mixture is cooled to room temperature, extracted with 0.5 M aqueous sodium hydroxide (4 x 450 mL), and dried over anhydrous sodium sulfate. The drying agent is removed by filtration, the filtrate is concentrated with a rotary evaporator, and the residual solvent is removed at 0.1 mm pressure to afford 40 g (99%) of yellow crystalline product, mp 96-100°C. 

A mixture of benzaldehyde la (0.53 g, 5 mmol), paraformaldehyde (1 g, 30 mmol) and solid sodium hydroxide (0.16 g, 4 mmol) were taken in an Erlen-meyer flask and placed in a commercial microwave oven operating at 2450 MHz frequency. After irradiation of the mixture for 25 s (monitored by TLC), it was cooled to room temperature, extracted with chloroform and dried over anhydrous sodium sulfate. Then the solvent was evaporated to give the corresponding ben-zylalcohol 2a in 90% yield exclusively without the formation of any side products. Preparative column chromatography with silica gel was used for further purification of the alcohols, eluting with petroleum ether (60/80)-CHCl3 (1 1). 

A mixture of benzaldehyde (1.06 g, 10 mmol), ethane-1,2-diol (0.62 g, 10 mmol) and commercial grade cadmium iodide (1.85 g, 5 mmol) were thoroughly mixed at room temperature in an Erlenmeyer flask and placed in a commercial micro-wave oven operating at 2450 MHz frequency. After irradiation of the mixture for 1.5 min (monitored vide TLC) it was cooled to room temperature, extracted with dichloromethane, washed with sodium thiosulfate and dried over anhydrous Na2S04- Evaporation of the solvent gave almost pure products and there was no evidence for the formation of any hydroxy ester or iodoester. Further purification was achieved by column chromatography on silica gel using 1 5 chloroform-petroleum ether as eluent. 

The relative effects of supercitical carbon dioxide density, temperature, extraction cell dimensions (I.D. Length), and cell dead volume on the supercritical fluid extraction (SFE) recoveries of polycyclic aromatic hydrocarbons and methoxychlor from octadecyl sorbents are quantitatively compared. Recoveries correlate directly with the fluid density at constant temperature whereas, the logarithms of the recoveries correlate with the inverse of the extraction temperature at constant density. Decreasing the extraction vessels internal diameter to length ratio and the incorporation of dead volume in the extraction vessel also resulted in increases in SFE recoveries for the system studied. Gas and supercritical fluid chromatographic data proved to be useful predictors of achievable SFE recoveries, but correlations are dependent on SFE experimental variables, including the cell dimensions and dead volume. 

Another matrix that was used to test the variation of modifier identity in SFE was shale rock. For these set of experiments a number of different compounds were chosen as target analytes, specifically pristane (C19H40), phytane (C20H47) and hexadecane (C15H34). Analogous to the study where the test matrix was sludge/fly ash, the modifier identity was varied and all other experimental parameters were kept constant (i.e. pressure, temperature, extraction duration, and modifier... 

Allow the reaction mixture to cool to room temperature, extract the product into diethyl ether (2 x 10 ml), and let the solvent to evaporate. 

SFE is carried out above the solvent critical point, and the properties of a supercritical fluid depend on pressure and change along with its density. These criteria determine the selectivity of the extraction medium. One fluid can therefore be used to extract a whole series of compound groups (depending on the pressure in the system, the temperature, extraction medium volume flow, and extraction time) and to separate the obtained extract into appropriate fractions. Selective fractionation is used, for example, to separate olfactory and gustatory substances in the extraction of hops for beer production. 

The photochromic effect was observed after both UV-irradiation and thermal ageing, but it was not dependent on the storage temperature. Extraction of the pulp had a slight effect. The most pronounced decrease was obtained if the pulp was impregnated with ascorbic acid, which probably works as a radical scavenger. The brightness increase follows the decrease in radicals in the pulp upon storage as monitored by ESR. 

Aromatics were separated by low-temperature extraction with a liquid mixture of SOs and CaHs. 

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