Organic Solvents deproteination with

Extraction of -lactam antibiotics from edible animal products should render residues that are bound to proteins soluble, remove most if not all of the sample proteins, and provide high yields for all analytes. Sample extraction/ deproteinization may be carried out with organic solvents and/or organic and... 

Sample extraction and deproteinization is usually accomplished with organic solvents including ethyl acetate (182-187, 189-192), acetone (193-196), methanol (177,197-200), acetonitrile (201,202), and ethanol (188). To optimize the extraction efficiency, acidification of the sample has been suggested by many workers (177, 188, 192, 197-199). In acidic conditions (pH 3), quinolones, being zwitterions, are fully protonated and, therefore, are becoming less bound by the matrix and more soluble in organic extraction solvents. Extraction of quinolones from food samples can also be accomplished using water (203), phosphate buffer, pH 9 (204), or trichloroacetic acid (205). 

In one, S-adenosyl-L-methionine was the methyl donor, norepinephrine was the substrate, while products of the reaction, normeranephrine and norparanephrine, were converted to the more stable and more easily obtained compounds vanillin and isovanillin, respectively, by periodate oxidation. The oxidation also allowed for the extraction of the incubation mixture with organic solvents such as ethyl acetate, affording a more complete deproteinization. 

In HPLC, alcohols and especially acetonitrile are often added to the sample to remove serum proteins. In CE, in addition to removing proteins, the presence of acetonitrile in the sample leads to stacking and indirectly improves precision of quantification because of the ability to increase the sample volume. We have analyzed several drugs and other natural compounds by CE after acetonitrile deproteinization. Protein removal can also be accomplished by alcohols such as ethanol and by acids such as perchloric. Precipitation with acids is less desirable in CE than with organic solvents because it increases the salt load. Following precipitation, proteins could also be dissolved in the appropriate buffers and assayed by CE. 

With the use of the inorganic sulfates or chlorides, protein precipitation does occur but the process is reversible. This does not occur when acids or organic solvents are used for protein precipitation, since the biological activity of the proteins in this case is irreversibly destroyed. On the other hand, use of mineral or organic acids, although valuable for deproteinization purposes, has raised prob-... 

Extraction/deproteinization has been performed by either vortexing liquid samples or homogenizing semisolid samples with acetonitrile (227, 382, 383, 386-392), methanol (14, 393-395), methanol/water mixtures (396-401), ethyl acetate (384,402-406), dichloromethane (379,380,407), and acetone (408,409). Nonpolar organic solvents, such as isooctane (410, 411) and toluene (407), have also been reported to work extremely well for extracting salinomycin and dimetridazole from chicken tissues, respectively. Sample extraction with these nonpolar solvents yields a cleaner extract and an easier workup than extraction with commonly used polar solvents. However, selecting an extraction solvent is critical in establishing an analytical method because it is closely related to the cleanup systems. 

Carbadox, olaquindox, and their monoxy- and desoxy- metabolites are amenable to extraction from tissues and eggs with polar organic solvents. Sample extraction/deproteinization is usually accomplished with ethanol (413), acetonitrile (414, 415), and acetonitrile/methanol (416-418). To reduce interferences and concentrate the analyte(s), the primary sample extract is further subjected to... 

Sample extraction and deproteinization is usually accomplished with nonpolar organic solvents at a specified pH. Organic solvents such as chloroform for the determination of cortisol in milk (529) dichloromethane/hexane (4 1) for the determination of free cortisol and its 21-acetate in milk (530) ethyl acetate for the determination of prednisolone, fluoroprednisolone, triamcinolone, and betamethasone in animal tissues (531) methylprednisolone in milk (532) fluoro-prednisolone in milk (533) and dexamethasone in milk (534) ethyl acetate in... 

One of the most studied biosorbent is chitin, which is an abundant biopolymer found in crustaceans, insects and fungus. This biopolymer is commercially purified by alkaline deproteinization, acid demineralization and decoloration by organic solvents of crustaceans wastes (Pastor, 2004). An additional stronger alkaline treatment of chitin produces deacetylated chitin. If the acetylation degree (DA) decreases at 39% or less, the biopolymer is named chitosan. Hence, the DA of chitin is variable and depends on the process conditions (alkali concentration, contact time, temperature, etc.), which produces DA values from 100 to 0%. Because of this, chitin is known as the biopolymer which has a DA from 100 to 40% likewise, when the chitinous biopolymer has DA lower than 40%, the biopolymer is named chitosan. Chitosan is, therefore, a biopolymer with structure very similar to that of chitin (see Figure 2) however, chitosan solubility is much greater, especially in acid mediums. 

The presence of large amounts of protein can have a major effect on the determination of free amino acids in plasma and samples must be deproteinized prior to analysis. Protein precipitation with either acid or organic solvent may be used, although care should be taken when acids are used to avoid interference in the chromatography from the acid itself. 

The analytical methods used to determine steroids in biological fluids include at least one extraction step. This step is performed directly on the preliminary deproteinized sample or after the cleavage of the conjugates. Diethyl ether, dichloromethane, chloroform, ethyl acetate, and other medium polar organic solvents, alone or in combination, can be used for extraction. The extract is then washed with aqueous sodium hydroxide to remove interfering acidic substances. Conjugates are extracted with more polar solvents or solvent mixtures, by use of high concentrations of salts in water. 

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