Vacuum extraction methods

Albertus, Frater], Simple vacuum extraction method. Alchem Lab Bulls 2, no. 1 (1970). rhttp //www.spagyria.com/alb.zipl. 

Modification of a simple vacuum extraction method. Parachemy 6, no. 1 (Winter 1978) 515-. 

The vacuum extraction method has been effectively applied to removing VOCs with low organic carbon content from well-drained soil, although it may also be effective for finer and wetter soils, but with comparatively slower removal rates. There are generally significant differences in the air permeability of various strata, which can influence process performance. Contaminants with low vapor pressure or high water solubilities are difficult to remove. 

Hydrogen analysis of coupons is perform by the hot vacuum extraction method. In the hot vacuum extraction apparatus, a small sample is heated to 1100 to 1400 °C (2010 to 2550 °F) for several minutes to reversibly release the absorbed hydrogen, followed by evolved gas measTirements. 

One example of such a comparison for several dehydrated foods against a vacuum-oven method is shown in Table IV. The data for the Fischer method are given for three different extraction times and are also shown graphically in Figure 4. The drying conditions were arbitrarily chosen to be 38 hours at 70° C. 

Despite the potential problems, two recent studies provide positive results. Matthews et al. (2000) analyzed the 5D of fluid inclusions in present-day cave carbonates from Soreq cave (Israel) using the method of thermal vacuum extraction and standard techniques on cave pool water from the same cave to estimate isotopic fractionation during measurement (Aex = 5Dextracted water - 8Dcave water). After subtracting Aex from 5D... 

The remedial technologies83-85,90-93 described in previous sections for gasoline release are applicable, for the most part, for remediation of DNAPLs. For example, the pumping or trench method for free products, vacuum extraction, biodegradation, pumping and treatment, soil flushing, and soil excavation and treatment are suitable for cleanup of various phases of DNAPLs. Again, because of... 

A shorter method of hydrolysis which may work as well follows dissolve 20 g alkaloid in 300 ml methanol and 300 ml 40% KOH and reflux two hours under N2 (if possible). Cool, saturate with C02 and evaporate in vacuum. Extract the residue with hot ethanol three times and dry, evaporate in vacuum the combined ethanol extracts to get (I). 

The vendor claims that Quick-Purge costs up to 50% less than traditional remediation methods such as pump-and-treat or soil vacuum extraction (D14386M). 

It is very common to combine methods in obtaining aroma isolates. The simultaneous distillation/extraction method previously described is an example. Another popular combination method initially involves the solvent extraction of volatiles from a food and then high-vacuum distillation of the solvent/aroma extract to provide a fat-free aroma isolate. This technique is broadly used today to provide high-quality aroma extracts for numerous purposes. The apparatus used in solvent removal has been improved upon to reduce analysis time and efficiency the modified method is termed solvent-assisted flavour extraction (SAFE) [16]. 

The major limitation of the vacuum pyrolysis method appears to be thermal decomposition of less volatile diazo compounds during the pyrolysis. The vacuum pyrolysis method was unsuccessful for the preparation of 1-naphthyl diazomethane and 3,5-dichlorophenyldiazomethane. However, such diazo compounds could be prepared from the corresponding tosylhydrazone salts by pyrolysi s in ethylene glycol and extraction of the aryldiazomethane into... 

Supercritical gas extractions Method B. Extractions were carried out in a 500 ml rocking autoclave fitted with a stainless steel liner. The Internal volume of the autoclave with liner was 420 ml. The autoclave was charged with coal and solvent, heated to and maintained at temperature for 1 h. The residue was washed out of the cooled reactor with acetone, filtered, washed with pyridine and then acetone and dried under vacuum. In some cases, g.c. analyses of the gases in the cooled reactor were carried out. 

The developed method for analysis of dynamical vacuum-extraction curves allows determination of the binding energy and total volume of the traps of different nature, as well as the diffusion constant of hydrogen in the probe under study. 

In liquid-liquid extraction (Fig. 3.6) two miscible solutes are separated by a solvent, which preferentially dissolves one of them. Close-boiling mixtures that cannot withstand the temperature of vaporization, even under vacuum, may often be separated by this technique. Like other contact processes the solvent and the mixture of solutes must be brought into good contact to permit transfer of material and then separated. The extraction method utilizes differences in the solubility of the components in the solvent. 

Chloride Content (as Cl) Transfer about 1 g of sample, previously dried in vacuum for 1 h and accurately weighed, into a 250-mL beaker, and add sufficient water to make 100 mL. Equip a pH meter with glass and silver electrodes, and set it on the + millivolt scale. Insert the electrodes and a motor-driven, glass stirring rod into the sample beaker. Add 1 to 2 drops of methyl orange TS. Stir, and add, drop wise, 10% nitric acid until a pink color appears, then add 10 mL in excess. Titrate the solution with 0.1 A silver nitrate to a reading of +1.0 millivolt on the pH meter. Each milliliter of 0.1 A silver nitrate is equivalent to 3.545 mg of chloride. Lead Determine as directed in the APDC Extraction Method under Lead Limit Test, Appendix IIIB. 

Our first separation method involved running the simultaneous steam distillation extraction under 100 mm vacuum in order to minimize heat effects. This was followed by extraction under atmospheric pressure in order to get more complete recovery. This atmospheric extraction was run for 10 days, using a fresh hatch of solvent each day (68-69). Approximately 10 times as much material was collected each day at atmospheric pressure as was collected under vacuum. Since Schultz, et. al. (70) showed that many non-water-soluble alcohols, esters, aldehydes, and ketones can he recovered by this system in less than 3 hours, the collection of a large amount of material after 10 days is indicative of a very complex and probably dynamic system. Gas chromatograms for these extracts (68.) and some compound identifications (69.) have been reported. (Other reports on the identification of volatiles from protein hydrolysates are given In references 71-75). Prelminary results have shown that the vacuum extracts are more attractive for the Medfly than the atmospheric ones. 

Vacuum Extraction. Vacuum extraction requires the sample to be heated in an evacuated system with determination of the evolved gas, either volumetricaUy or by differential pressure measurement. This method is recommended whenever possible because of the speed and precision, particularly where the amount of hydrogen is below 0.01%. 

The vacuum SDE method confirmed the presence of nearly all of the constituents identified using dynamic headspace sampling and revealed many additional compounds. The method was more effective in extracting the less volatile const rtuents such as long chain esters. In contrast to the previous runs this sample was chromatographed on a nonpolar DB-1 column. The constituents identified in the pulp sample prepared by vacuum SDE are listed in Table VI. The %area values should be considered as only approximate since known pineapple constituents such as ethyl acetate, methyl propanoate, methyl 2-methylpropanoate, ethyl propanoate, ethanol, propyl acetate, and ethyl 2-methylpropanoate co-elute with the solvent peaks and hence could not be included in the quantitation. 

In these equations P is the headspace pressure in atmospheres, a is the gas-to-seawater ratio (Vg/V ), and is the total volume of the flask (here 1 L). By this procedure the initial concentration of a dissolved gas (C f) in seawater can be determined. Normally single extractions are done, but subsequent extractions can be used to check the amount of gas remaining in the seawater. The uncertainties associated with the headspace method can be evaluated by referring to Equation 2. In addition to the headspace gas concentration, Cg, the uncertainty in C f is dependent on the uncertainties in H and the ratio a. By using a propagation of error procedure on Equation 2, the uncertainties associated with the vacuum extraction flask can be estimated for different gases (2). The results show that for a gas that is not very soluble (H > 3), the total uncertainty is 5 %. For a more soluble gas H < 0.5) whose Henry s constant is not accurately known in seawater, the uncertainty is 30 %. 

Comparisons of the vacuum extraction flask method versus the purge-cryogenic trap method were made on duplicate seawater samples. The results are shown in Table II. The compounds measured represent a wide range of Henry s constants (solubilities) and provide a representative evaluation of the two methods. In Run 1 of Table II the CHCI3 concentration was not measured. In Runs 1-4 the CF2CI2 concentrations were below the detection limit of the GC-ECD used for the analysis. The comparisons are for single samples and agree reasonably well except for 1,1,1-trichloroeth-... 

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