Solid-water distribution coefficient compound

To assess the extent to which a compound is associated with solid phases in a given system at equilibrium (see below), we need to know the ratio of the compound s total equilibrium concentrations in the solids and in the aqueous solution. We denote this solid-water distribution coefficient as Kid (e.g., in L kg 1 solid) ... 

Since the open water column is nearly pure water (op =1, rs p = 0), for compounds with small to moderate solid-water distribution ratios (Kd < 10 m3kg ), the above equilibrium partition coefficient can be simplified to ... 

Figure 9.28. The distribution of nonpolar organic substances between aquatic solids and water (as given by the distribution coefficient Kp) is dependent upon the lipophilicity of the compound and the organic C content of the adsorbing material (foe = weight fraction). The solid phases considered here are coastal sea and lake sediments, river sediments, solids from aquifers and biomass (activated sludge). The octanol/water distribution coefficients are, respectively 500, 2400, 11,200 and 52,000 for chlorobenzene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene and 1,2,4,5-tetrachlorobenzene. (Modified from Schwarzenbach and Westall, 1980).

Paschke, A. and Popp, P. 2003, Solid-phase microextraction fibre-water distribution constants of more hydrophobic organic compounds and dieir correlations widi octanol-water partition coefficients. J. Chromatogr. A 999 35-42. 

For air-water systems, this equation is known as Henry s law. For solids-water systems, the equilibrium constant is known as the partition coefficient (Ky) or distribution constant (KA). Partition coefficients are available for many organic chemicals from laboratory and field measurements. As organic carbon (OC) present in water (dissolved organic carbon, or DOC), sediment, or soil is the main sink for hydrophobic organic contaminants, the partition coefficients for these compounds are often adjusted (normalized) with respect to the organic carbon content of these compartments ... 

The hypothesis has been advanced that changes in relative concentrations of lipid type compounds, when comparing aquatic biota and their habitat, can be explained in large part by an estimate of their tendency to partition into tissues which has been related to octanol/water partition coefficients - K s (, 22). Table Vll presents tabulated data for and water to biota bloaccumu-latlon concentration factors calculated from data in Tables III and IV. Representative data from Table Vll are plotted in Figure 6 in the manner of Mackay (21) and Chlou (22), who have reviewed data on bloaccumulatlon of neutral hydrophobic compounds in aquatic biota. The solid line Is the expected distribution of data based on Chlou s review (22) of predictability for equilibrium situations. Our data is different in an absolute sense than the data used by Mackay and Chlou, because they used concentrations in biota... 

Lipophilicity of a molecule is measured by its distribution behavior in a biphasic system either liquid-liquid (partition coefficient in 1-octanol-water) or solid-liquid (retention in RP-TLC or RP-HPLC) systems. According to definition suggested by lUPAC lipophilicity expresses the affinity of a molecule for a lipophilic environment. A reference scale representing lipophilicity appears to be the solute distribution between octanol and water. Berthod Carda-Broch (Berthod Carda-Broch) proposed another lipophilicity scale measuring ionic liquid BMIM PFg-water distribution constants. Relationship between the obtained values and respective octanol-water coefficients for a series of aromatic compounds differing in acid-base properties revealed that only the neutral compounds or ionizable ones with zwitterionic properties showed similar distribution behavior in the... 

Unfortunately, cation exchange does not lend itself to simple mathematical description as does idealized sorption of hydrophobic organic compounds. For low concentrations of a contaminant ion in a constant background of other ions, however, the ion exchange process often is treated approximately as a linear partitioning process, and use of a simple retardation factor in a transport model may be justified. Distribution coefficients for ionic contaminants in an aquifer are usually determined experimentally. Typically, a batch test is performed in which the ionic concentration on a fixed volume of aquifer solids and the ionic concentration in the associated pore waters are analyzed the distribution coefficient is taken as the ratio of the concentrations. Because sorption by ion exchange is affected by the concentrations of all other ions in the groundwater, the... 

The second factor which frequently leads to difficulties in isolation and purification arises from the exceptional solvent properties of amides—both liquid and solid. Many ionic compounds such as salts, water, and a large variety of covalent compounds, including aromatic hydrocarbons, have an appreciable solubility in many amides. The amides, in turn, may exhibit an appreciable solubility in very diversified solvents. Clearly, this situation may bedevil a synthesis with extremely complex solubility distribution coefficient problems. Vapor phase chromatography has been used in our laboratories to advantage in determining whether the amide has been adequately separated from... 

Partition coefficients are used to describe the distribution of nonpolar organic compounds between water and organisms. It can be viewed as a partitioning process between the aqueous phase and the bulk organic matter present in biota (Schwarzenbach et al. 1993). The premise behind the use of equilibrium models is that accumulation of compounds is dominated by their relative solubility in water and the solid phases, respectively. Equilibrium models, therefore, rely on the following assumptions (Landrum et al. 1996) ... 

Palytoxin is a white, amorphous, hydroscopic solid that has not yet been crystallized. It is insoluble in nonpolar solvents such as chlorophorm, ether, and acetone sparingly soluble in methanol and ethanol and soluble in pyridine, dimethyl sulfoxide, and water. The partition coefficient for the distribution of palytoxin between 1-butanol and water is 0.21 at 25°C based on comparison of the absorbance at 263 nm for the two layers. In aqueous solutions, palytoxin foams on agitation, like a steroidal saponin, probably because of its amphipathic nature. The toxin shows no definite melting point and is resistant to heat but chars at 300°C. It is an optically active compound, having a specific rotation of -i-26° 2° in water. The optical rotatory dispersion curve of palytoxin exhibits a positive Cotton effect with [a]25o being -i-700° and [a]2,j being +600° (Moore and Scheuer 1971 Tan and Lau 2000). 

Sorbent extraction Sorbent extraction makes use of the differential distribution of the dissolved compounds between the solid sorbent and water. The use of organic porous polymers is advantageous for the extraction of organic compounds from water because (1) the partition coefficients of compounds in a polymer-water system reach infinity if the correct polymer is selected for the types of contaminants present (2) adsorption of water itself on the polymer is minimal (3) the wettability of the polymer with water makes possible satisfactory transport of the substance toward the polymer surface and (4) the polymer is inert. 

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