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Common solvents cleaning examples

Beverages and seawater are examples of aqueous solutions, solutions in which the solvent is water. Aqueous solutions are very common in everyday life and in chemical laboratories for that reason, most of the solutions mentioned in this text will be aqueous. Nonaqueous solutions are solutions in which the solvent is not water. Although they are less common than aqueous solutions, they have important uses. In dry cleaning, the grease and dirt on fabrics are dissolved in tetrachloro-ethene, C2C14, a compound of carbon and chlorine. There are also solid... [Pg.90]

The solvent extracts can be cleaned up by traditional column chromatography or by solid-phase extraction cartridges. This is a common cleanup method that is widely used in biological, clinical, and environmental sample preparation. More details are presented in Chapter 2. Some examples include the cleanup of pesticide residues and chlorinated hydrocarbons, the separation of nitrogen compounds from hydrocarbons, the separation of aromatic compounds from an aliphatic-aromatic mixture, and similar applications for use with fats, oils, and waxes. This approach provides efficient cleanup of steroids, esters, ketones, glycerides, alkaloids, and carbohydrates as well. Cations, anions, metals, and inorganic compounds are also candidates for this method [7],... [Pg.24]

In contrast, the most common industrial halo-genated solvents such as methylene chloride, chloroform, perchloroethylene, and carbon tetrachloride have long been identified as suspected human carcinogens. Benzene and other aromatic hydrocarbons have also been associated with the causation or promotion of cancer in humans and animals. All of these substances are widely used because of their excellent solvent properties in a wide range of applications. Nevertheless, regulations have been issued in the United States, for example (under the Clean Air Act) to control many of these chemicals... [Pg.308]

The relative distance which a compound travels up a tic plate depends on two factors, its polarity and that of the solvent. In the same solvent, the more polar the compound, the more tightly it is bound to the silica (or alumina) and the less it travels. There are some common trends, and with experience, it is often possible to predict whether a product will be less or more polar than the starting material. For example when a ketone, or ester is reduced, the resultant alcohol is almost always significantly more polar, and a clean transformation to a lower running spot will indicate a successful reaction. If the polarity of the solvent used for elution is increased the spots... [Pg.149]

Solubility can also be enhanced by the presence of other compounds. This phenomenon is caused by one or more compounds acting as solubility enhancers for other compounds present on a surface. This phenomenon is sometimes called the local cosolvent effect. A typical method of enhancing contaminant solubility is through the addition of a small amount of secondary solvent to the SCF cleaning system. Alcohols are commonly used in this manner to increase solubilities of more polar contaminants. However, more subtle local cosolvent effects have been observed. Perhaps a classic example was first reported by Kumik and Reid. In their study, they observed that the solubilities of both naphthalene and benzoic acid in supercritical CO2 were enhanced by 107% and 280%, respectively, when both species were present. It has also been shown that there needs to be enough of a secondary component present in solution about the local contaminant environment to enhance the solubility of another compound, This example demonstrated that an excess of phenanthrene promoted the solubility of anthracene in supercritical COj, but since anthracene was only present in very small quantities, it did not help to enhance the overall solubility of phenanthrene. A... [Pg.27]

In addition to releases from the various components or activities that make up the production and distribution system for petroleum products (the oil system), many older waste sites show TPH-related site contamination. Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) site descriptions often mention petroleum, oil and grease, or petroleum, oil, and lubricants (POL) as present at a former waste disposal site. An example is given below for a waste oil recycling site, where TPH-type chemicals were obviously a common site contaminant. The CERCLA clean-up actions, however, focus on a range of specific hazardous or toxic chemicals. Some of the specific chemicals (e.g., toluene) would show up in a TPH test, but the chlorinated solvents and metals do not. Since a site cannot be prioritized for CERCLA attention if the only problem involves TPH site... [Pg.86]

Pesticide Residues Pesticide residue analysis often requires elaborate sample preparation procedures and analyte enrichment, which might involve extraction (homogenization, solvent extraction), clean-up (solvent partitioning, GPC, SPE), and analyte derivatization.21 Examples are shown in the environmental applications section. Common pesticide residues found in food crops, vegetables, or fruit are ... [Pg.169]


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