Sorption phase-water partition coefficient

In equilibrium sampling, the exposure time is sufficiently long to permit the establishment of thermodynamic equilibrium between the water and sorption phases. In this case the dissolved analyte concentration can be estimated using the sorption phase-water partition coefficient (Ksw) ... 

The base set of partition coefficients needed for most multimedia models include the Henry s law constant (JCh) to describe partitioning between air and water, partition coefficients between water and various solid phases in soils, sediments, and particulate matter in the water coliunn (fCa), and a coefficient describing partitioning between air-borne particles and air (Kp). If not available from direct experimental measurements, soUd phase-water partition coefficients are often derived from the organic carbon-water partition coefficient, Kqc (Eq. 4), the underlying assumption being that sorption into organic matter dominates the overall sorption to bulk solid material. 

Vowles and Mantoura [38] determined sediment-water partition coefficients and the high-performance liquid chromatography capacity factors for 14 alkylbenzene and polyaromatic hydrocarbons. The partition coefficients correlated well with the alkyl-cyano capacity factors, and it was concluded that this phase gave a better indication of sorption on sediment than either the octanol or octadecylsilane phases. 

Nakamura, M., Suzuki, T., Amano, K., Yamada, S. (2001) Relation of sorption behavior of agricultural chemicals in solid-phase extraction with their n-octanol/water partition coefficients evaluated by high-performance liquid chromatography (HPLC). Anal. Chim. Acta 428, 219-226. 

It has been argued that the Kqa values can be used as a unifying property for describing volatilization of POPs from soils and sorption to aerosols. The limited experimentally obtained values typically are supplemented by estimates from octanol-water and air-water partition coefficients. The value of condensation temperature lies in its ability to estimate sorption of atmospheric contaminants to aerosols (Bidleman, 1988). At Tc, the chemical is equally partitioned between the gas phase and aerosols. Since POPs exist in the atmosphere both as gases (vapor phase), and in condensed form adsorbed to aerosol particles, the characteristic temperature of... 

The sorption coefficient, ATp—essentially a distribution coefficient (mol kg solid phase)/mol (liter water) —can be expressed as a function of organic carbon content,/oc (fraction by weight), and the octanol-water partition coefficient... 

In summarizing reversed-phase SPE, both the and the log of the octanol-water partition coefficient of the compound are related to the aqueous solubility of the analyte, although the relationship is not always straightforward because there are other factors that affect solubility of an analyte but that do not affect sorption, such as crystal lattice energy for solids. In spite of this factor, one could theoretically estimate the from the solubility of the analyte and relate this solubility to the capacity of the solute for the reversed-phase sorbent. The ability to use solubility to predict capacity is also addressed... 

Hydrophobic Effect. The partitioning of a substance from an aqueous phase into (or onto) another phase due to its hydrophobicity. Often characterized by an octanol-water partitioning coefficient. See also Solvent-Motivated Sorption. 

Octanol-Water Partition Coefficient. The partitioning coefficient of a compound between octanol and water, that is, between specific nonpolar and polar phases. Used as an indication of the tendency of a compound to partition between oil and water phases. A variety of empirical equations estimate such partitioning of a compound on the basis of its octanol-water partition coefficient. See also Solvent-Motivated Sorption. 

Solvent-Motivated Sorption. Sorption that occurs as a result of the hydrophobicity of a compound. Accumulation of the compound at the interface or in the other phase is not due to its affinity for that phase so much as to its disaffmity for the initial phase. Such sorption occurs for organic contaminants in the environment. This kind of sorption can often be related to the octanol-water partitioning coefficient. 

The soil organic carbon-water partition coefficient (K ) is a parameter that is used to express the extent to which an organic chemical partitions itself between the soil and solution phases (i.e., dissolved in the soil water). is defined as the ratio of the chemical s concentration in a state of sorption (i.e., adhered to soil particles) and the solution phase. Thus, for a given amount of a chemical, the smaller the value, the greater the concentration of the chemical in solution. Chemicals with a small value are more... 

From an environmental impact standpoint, the four most important physical properties of PCBs are very low water solubUlty and vapor pressure, high octanol/water partition coefficients, and stability or persistence (NRC, 1979). The five mechanisms by which PCBs can be transported in the soil are as a dissolved material in the water by sorption as an emulsion with water as an immiscible oUy Uquid phase and as a discrete fluid. 

A large number of organic chemical pollutants are hydrophobic, literally "afraid of water." These chemicals have limited solubility in water but do tend to dissolve easily into oils, fats, nonpolar organic solvents, and solid-phase organic carbon, which is ubiquitous in the environment. To a first approximation, the partition coefficient for many hydrophobic chemicals is not especially sensitive to the exact source or nature of the organic carbon. Accordingly, Kqc, the organic carbon-water partition coefficient, can be used to estimate the extent of sorption. Kqc can be expressed as... 

Pollutants with high VP tend to concentrate more in the vapor phase as compared to soil or water. Therefore, VP is a key physicochemical property essential for the assessment of chemical distribution in the environment. This property is also used in the design of various chemical engineering processes [49]. Additionally, VP can be used for the estimation of other important physicochemical properties. For example, one can calculate Henry s law constant, soil sorption coefficient, and partition coefficient from VP and aqueous solubility. We were therefore interested to model this important physicochemical property using quantitative structure-property relationships (QSPRs) based on calculated molecular descriptors [27]. 

As we have seen in (Eq. 4.40) and in Fig. 4.14, the distribution (or partition) coefficient for the (ab)sorption of a non-polar organic solute onto a solid phase can be estimated from the octanol-water coefficient Kow (see Eq. 4.42)... 

The presence of a residual hydrocarbon phase in soils or sediments has been shown to increase the soil- or sediment-water distribution coefficients of poorly water-soluble organic contaminants [463,464]. Such petroleum-hydrocarbon-based phases have been shown to function as effective partition media for PCB congeners [467]. In general, sorption of contaminants by soils and sediments reduces their bio availability to microorganisms [468,469]. In this fashion, the... 

It is important to point out that sorption of simple ions is not affected only by charge non-uniformity. The non-homogeneity of the dielectric constant in the membrane is also significant. This becomes particularly evident in the case of uncharged hydrophobic membranes of the type commonly used for water desalination by reverse osmosis, where dielectric exclusion of the electrolyte from the membrane phase is the only sorption mechanism in operation 127). If the swollen membrane is treated as a homogeneous phase, the ionic partition coefficient Sj is expected to be... 

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