Solvent-flushing processes

Lower alcohols (e.g. methanol, ethanol, propanol), ketones (e.g. acetone), and alkyl amines are often used in solvent-flushing processes (Li, Cheung, and Reddy,... 

Every solvent cleaning process (being implemented in any of the five cleaning machines above) has three additional tasks to perform in addition to removing the soil from a surface by dissolving it into a solvent. They are to (1) refine the soiled solvent for reuse as a flush or rinse fluid, (2) concentrate the soil removed from parts into a small amount of solvent, and (3) remove that concentrate of soil from the cleaning machine so the concentrate may be disposed of properly. ... 

Since the early 1960s, there has been much discussion in the literature of syringe technique during the injection process. Most of this related to facilitating rapid and quantitative sample transfer into the inlet, despite slow, nonreproducible manual operation. These techniques, including cold needle, hot needle, solvent flush, and inclusion of air along with the sample, are not discussed in detail here, as for most hot injection methods (split and splitless), a fast autoinjector, readily available for all gas chromatographs and used as the standard in most industries, will provide excellent quantitative injections. For more information on manual injection techniques the reader is referred to Reference 3. 

Diafiltration If a batch process is run so that the permeate is replaced by an equal volume of fresh solvent, unretained solutes are flushed through the system more efficiently. A major use of UF is fractionation, where a solvent, a retained solute and an unretained solute are present. An example is whey, containing water, protein, and lactose. If the retention of protein is I and the retention of lactose is 0, the concentration of protein in the retentate rises during UF. The ratio of protein to lac tose rises, but the feed concentration of lactose is unchanged in retentate and permeate. Diafiltration dilutes the feed, and permits the concentration of lactose to be reduced. Diafiltration is used to produce high-purity products, and is used to fractionate high-value products. R is always 0 for eveiy component. 

Offline cleaning can, and should, be entirely successful, with the simplest methods requiring, say, a 10 or 15% inhibited hydrochloric (muriatic) acid solution that is allowed to soak for some hours before neutralization, flushing, and refilling. Where the waterside deposit analysis reveals complex scales, however, it may be necessary to employ several different cleaning solvents. These solvents are added in a multistep process. 

Introduction of the flushing solution may occur within the vadose zone, the saturated zone, or both. Flushing solutions may consist of plain water, or surfactants, co-solvents, acids, bases, oxidants, chelants, and solvents. The infiltrating flushing solution percolates through the soil and soluble compounds present in the soil are dissolved. The elutriate is pumped from the bottom of the contaminated zone into a water treatment system to remove pollutants. The process is carried out until the residual concentrations of contaminants in the soil satisfy given limits. 

Some pipets are calibrated TC. Such pipets are used to transfer unusually viscous solutions such as syrups, blood, etc. With such solutions, the wetness remaining inside after delivery is a portion of the sample and would represent a significant nontransferred volume, which translates into a significant error by normal TD standards. With TC pipets, the calibration line is affixed at the factory so that every trace of solution contained within is transferred by flushing the solution out with a suitable solvent. Thus, the pipetted volume is contained within and then quantitatively flushed out. Such a procedure would actually be acceptable with any TC glassware, including the volumetric flask. Obviously, diluting the solution in the transfer process must not adversely affect the experiment. 

The chloroform solution of lipids (Solution A) is placed in a 50-mL round-bottomed spherical Quick-fit flask. Following evaporation of the solvent in a rotary evaporator at about 37°C, a thin lipid film is formed on the walls of the flask. The film is flushed for about 60 seconds with oxygen-free nitrogen (N2) to ensure complete solvent removal and to replace air. Two milliliters of distilled water and a few glass beads are added into the flask, the stopper is replaced, and the flask shaken vigorously by hand or mechanically until the lipid film has been transformed into a milky suspension. This process is carried out above the liquid-crystalline transition temperature (7/) of the phospholipid component of liposomes (> 7/) by prewarming the water... 

Less commonly, other experimental conditions may need to be controlled. For example, it may be that the presence of O2 in solution affects the reaction, in which case stock solutions and the reaction mixture should be flushed and then kept saturated with an inert gas (nitrogen or, preferably, argon). For reactions in nonaqueous solvents, of course, water may need to be rigorously excluded. And sometimes, a chemical process is affected by light if any of the species involved is light sensitive. In this event, stock solutions and the... 

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