Organic phase-water partition coefficient

Table 10.2 Organic Phase-Water Partition Coefficients of Some Organic Compounds for Various Organic Phases Octanol (o), Triacylglycerides (tag), Liposomes (lips), Proteins (prot), Cutin (cut), and Lignin (lig). (All values except Kiow in L kg"1 org. phase for 20-25°C if not otherwise stated. Note that the densities of the organic phases are close to 1 kg org. phase L 1 org. phase.)...

Experimental values of Koc appear to be in excellent agreement with Koc estimated from experimental Kow value. Recalling that log Koc estimates from solubility relations were 6.39 - 5.64 and 6.24 -6.49, it is clear that our experimenatl values for the water solubility, octanol-water partition coefficient, and soil organic carbon-water partition coefficient are internally consistent. We attribute this to having taken steps to minimize losses to unknown parts of the equilibrating system, and to correct for losses by the analysis of dioxin in each of the phases involed in the partition system. 

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. 

As mentioned before, POP transport in the environment depends on their physicochemical properties [40-54], and these include saturated vapor pressure, solubility, Henry s law constant, octanol-water, octanol-air, and organic carbon-water partition coefficients. The saturated vapor pressure characterizes the capability of a substance to be transferred to the gaseous state. Eollowing the study of Wania and Mackay [40], the efficiency of POP condensation with subcooled liquid pressure (p°L) at 25°C above 1 Pa is very low. POPs with a vapor pressure between 1 and 10" Pa are condensed at a temperature of about -30°C and their deposition may be expected mostly in the polar latitudes. POPs with a vapor pressure of subcooled liquid from 10" to 10" Pa are condensed at a temperature above 0°C and they may reach to the middle latitudes. EinaUy, POPs of low volatility with a vapor pressure of subcooled liquid below 10" Pa are practically not vaporized and these substances may be transported and deposited as fine aerosols or coarse particles [39]. Using the vapor pressure of the subcooled liquid it is possible to characterize the partitioning of a POP between the gas phase and the solid phase of the atmospheric aerosol. The POPs having a lower vapor pressure are better bound with... 

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... 

Adsorption to soil organic carbon is measured as the organic carbon/water partition coefficient (Koc), calculated as the distribution among a soil and an aqueous phase, normalised to the organic carbon content of the soil [27]. 

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... 

The logarithm of the 1 -octanol - water partition coefficient, denoted log Kq j or log P, indicates the distribution of the compound between the organic and the water phase. For highly lipophilic compounds, the log P is determined via reversed-phase thin-layer chromatography, giving the so-called log P tlc value1. 

Burkhard, L. P, Kuehl, D. W., Veith G. D. (1985c) Evaluation of reversed phase liquid chromatograph/mass spectrometry for estimation of n-octanol/water partition coefficients of organic chemicals. Chemosphere 14, 1551-1560. 

McDuffie, B. (1981) Estimation of octanol/water partition coefficient for organic pollutants using reversed phase HPLC. Chemosphere 10, 73-83. 

Sangster, J. (1989) Octanol-water partition coefficients of simple organic compounds. J. Phys. Chem. Ref. Data 18, 1111-1230. Sangster, J. (1993) LOGKOW, A Databank of Evaluated Octanol-Water Partition Coefficients. 1st Edition, Montreal, Quebec, Canada. Sarna, L.P., Hodge, P.E., Webster, G.R.B. (1984) Octanol-water partition coefficients of chlorinated dioxins and dibenzofurans by reversed-phase HPLC using several C18 columns. Chemosphere 13, 975-983. 

The tendency of the compound to be absorbed (to dissolve) in the organic phase is related to the dissolution of the compound in n-octanol, i.e., to the chemical s octanol-water partition coefficient... 

The most common partition coefficient encountered in environmental work (Sect. 2.1.4) is the octanol water partition coefficient (K0VI) and the solid phase carbon-water partition coefficient (Koc). A partition coefficient for dissolved organic matter-water (i. e., Kd ()M) or dissolved organic carbon-water (i. e., Kd oc) occasionally appears in the literature. In the case of PCBs, Boyd and Sun [378] defined a partition coefficient for residual transformer oil and water as Kd oil, while Sun and Boyd [379] defined a coefficient for PCB dielectric fluid-water as Kd pen-These authors [378,379] identified a total partition coefficient that com-... 

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