Purification Purified

Purchasing research Pure alcohols Pure ethyl silicate Pure Natural Pure silicon PUREX Purex process PUR foams Purgatives Purging Purification Purified Pork Insulin... 

Purification purified by silica gel chromatography using a mixture of CH2Cl2/n-pentane (70 30) as eluent... 

Figure 10. Rhodamine 6G perchlorate in ethanol (4.3 x 10 M). Absorbance E vs. wavenumber. 0> Dye before purification , purified dye —, expected according to Eq. (3).

PAne (PANi, SFST, 280 000 g/mol), DCAd (DCAA, Merck, 9 %) and 2-acrylamido-2-methyl-l-propane sulfonic acid (AMPSA, Aldrich, 9 %) were all used without arty further purification. Purified SWCNT (SWNTs, Hipco CNI) were used as pirrchased and contained 5 w % iron residue as determined by elemental analysis. 

Purification Purify abouf 50 mg of the product by dissolving it in a minimum amount of boiling dichloromefhane in a fesf fube. Using a Pasteur pipet, rerrxive the upper. 

Purification Purify the crude product by recrystallization from the minimum volume of hot water. If necessary, decolorize the hot solution and use a preheated funnel for the hot-filtration step to prevent premature crystallization of the product in the... 

Purification purified by distillation at 82 °C/760 mmHg. Handling, Storage, and Precautions unusually stable for an aldoketene with respect to dimerization and decomposition. Samples stored neat under nitrogen at room temperature show no noticeable decomposition after several months. 

Purification purified by column chromatography (CH2CI2/ MeOH, or CH2Cl2, or CH2Cl2/acetone ). 

Cleavage of the peptide from the resin weigh about 500 mg of dried resin into an Erlenmeyer flask and add 50 mL of TFA/TIS/water (96 2 2) mixture see Note 9). Stir the reaction mixture for at least 2 h at room temperature. Filter the reaction mixture and evaporate almost all the TFA by rotary evaporator. Add 50 mL of cold diethyl ether and extract three times with 50 mL of solution A/solution B mixture (50 50, v/v) (solution A FljO/O.OS % TFA solution B 90 % aceto-nitrile/10 % H2O/O.O45 % TFA). Collect the water layer and lyophilize for purification. Purify the crude linear peptide with RP-HPLC before cyclization and folding. 

The general techniques for polysaccharides characterization were described previously[5]. The usual techniques used to characterize their properties are briefly described in the following but it is pointed out that the most important step remains the step of purification. Purified anionic polysaccharides are isolated under the sodium salt form as described before[5,8] neutral polysaccharides are purified by filtration and precipitation with ethanol[10,ll] chitosan is recovered by precipitation in slightly alkaline aqueous conditions[12]. 

Reducing waste from feed impurities which undergo reaction. If feed impurities undergo reaction, this causes waste of feed material, products, or both. Avoiding such waste is most readily achieved by purifying the feed. Thus increased feed purification costs are traded off against reduced raw materials, product separation, and waste disposal costs (Fig. 10.2). 

Perhaps the most extreme situation is encountered with purge streams. Purges are used to deal with both feed impurities and byproducts of reaction. In the preceding section we considered how the size of purges can be reduced in the case of feed impurities by purifying the feed. However, if it is impractical or uneconomical to reduce the purge by feed purification, or the purge is required to remove a byproduct of reaction, then the additional separation can be considered. 

Students should carry out the purification by steam distillation of (a) crude nitrobenzene or chlorobenzene, or of (b) crude naphthalene, o-nitrophenol (p. 170) or />-tolunitrile (p. 194) as examples of solid compounds which may also be purified in this way. When the distillation is complete, disconnect the tubing (Fig. 15) between C and D before removing the flame from under D, otherwise the contents of C will be sucked back into D as the latter cools. 

An account will be given in this and the two following Sections of a number of inorganic reagents which find application in organic chemistry. No attempt will be made to describe the preparation of those reagents which can be purchased at a reasonable cost. In some cases, where the purified reagents are somewhat expensive, the methods of purification from the technical products will be outlined. 

Solid phase peptide synthesis does not solve all purification problems however Even if every coupling step m the ribonuclease synthesis proceeded in 99% yield the product would be contaminated with many different peptides containing 123 ammo acids 122 ammo acids and so on Thus Memfield and Gutte s six weeks of synthesis was fol lowed by four months spent m purifying the final product The technique has since been refined to the point that yields at the 99% level and greater are achieved with current instrumentation and thousands of peptides and peptide analogs have been prepared by the solid phase method... 

Isotope Dilution Another important quantitative radiochemical method is isotope dilution. In this method of analysis a sample of analyte, called a tracer, is prepared in a radioactive form with a known activity. Ax, for its radioactive decay. A measured mass of the tracer, Wf, is added to a sample containing an unknown mass, w, of a nonradioactive analyte, and the material is homogenized. The sample is then processed to isolate wa grams of purified analyte, containing both radioactive and nonradioactive materials. The activity of the isolated sample, A, is measured. If all the analyte, both radioactive and nonradioactive, is recovered, then A and Ax will be equal. Normally, some of the analyte is lost during isolation and purification. In this case A is less than Ax, and... 

Independent Assays for Provings Virus Removal. Retrovimses and vimses can also be present in culture fluids of mammalian cell lines (15,24). Certainly the absence of vims can be difficult to prove. Model vimses, eg, NIH Rausher leukemia vims and NZB Xenotropic vims, were spiked into fluids being purified, and their removal subsequently vaUdated when subjected to the same purification sequence as used for the product. 

Chemical Conversion. Except for control of nitrogen impurity levels, the same chemical conversion methods used for nitrogen purification at low flow rates can also be used for argon purification. Although used less commonly for argon purification than for nitrogen purification, these chemical conversion methods are appHed in point-of-use purifiers located close to where the gas is consumed. 

In some cases the chemical manufacturer purifies a portion of this intermediate stream to make a high purity product. In other cases, the chemical manufacturer sells a low purity product to a gas company and the gas company purifies it to make a high purity product. In both bases, purification is done on a continuous basis, rather than cylinder by cylinder. The purification processes tend to utilize standard methods. 

Point-of-Use Purification. For the user of cylinder quantities of reactive specialty gases, there are only a limited number of ways to remove impurities and obtain high purity. Specialized point-of-use purifiers have been developed that purify small streams of many important reactive gases. Whereas these point-of-use purifiers cannot remove all important impurities, they are usually effective for removing the contamination added by the users gas distribution system, mostly air and moisture. 

Purification. Unsubstituted di- -xylylene (DPXN) is readily purified by recrystaUization from xylene. It is a colorless, highly crystalline soHd. The principal impurity is polymer, which fortunately is iasoluble ia the recrystaUization solvent and easily removed by hot filtration. 

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