Organics compounds, partitioning

In the vadose (unsaturated) zone, liquid organic compounds partition into four distinct but related phases NAPL adsorbed onto soil particles, free-phase NAPL, soluble constituents in soil water, and vapor-phase components as part of the soil... 

Gustafsson, O., and P. M. Gschwend, Hydrophobic organic compound partitioning from bulk water to the water/air interface , Atmos. Environ., 33,163-167 (1999). 

The manner in which a given compound is deposited is determined by the form in which it is present in the atmosphere. Semi-volatile organic compounds partition between the gas and particle phases. The lower the vapour pressure of a... 

Sorption of organic contaminants onto aquifer solids is frequently described as a partitioning process, where the hydrophobic organic compound partitions into natural organic material associated with the aquifer solids [8]. Sorption can be characterized as either an equilibrium or rate-limited phenomenon. Equilibrium sorption can be modeled as either a linear or non-linear process. Equilibrium sorption may be assumed when the flow of groundwater and other processes affecting contaminant transport are slow compared to the rate of sorption. In this event the sorption of the contaminant can be considered instantaneous. If we assume equilibrium sorption, the relationship between sorbed and aqueous contaminant concentrations may be described by a sorption isotherm. 

Many organic compounds partition into the organic matrix of soils and sediments, and these associated residues may be both less toxic and less amenable to biodegradation than the free compounds. This presents an adverse prognosis for bioremediation. This has been discussed in Chapter 3, Sections 3.2.2 and 3.2.3, and in Chapter 4, Section 4.6.3. 

The extent to which an organic compound partitions out of water onto soil is determined by physical-chemical properties of both the soil and the compound. The soil s organic matter content is the single best characteristic for estimating the amount of soil adsorption of pesticides and other organic molecules. The partition, or sorption, coefficient of the organic molecule Koc (equal to ATp/SOM) is rather independent of soil type. This suggests that SOM is the principal soil component responsible for pesticide sorption and that the role of SOM is similar in different soils. 

A slightly polar organic compound partitions itself between ether and water phases. The Kp (partition coefficient) value is 2.5 in favor of the ether solvent. What simple procedure could you use to increase this Kp value ... 

The constant K is termed the distribution or partition coefficient. As a very rough approximation the distribution coefficient may be assumed equal to the ratio of the solubilities in the two solvents. Organic compounds are usually relatively more soluble in organic solvents than in water, hence they may be extracted from aqueous solutions. If electrolytes, e.g., sodium chloride, are added to the aqueous solution, the solubility of the organic substance is lowered, i.e., it will be salted out this will assist the extraction of the organic compound. 

This experiment provides an alternative approach to measuring the partition coefficient (Henry s law constant) for volatile organic compounds in water. A OV-101 packed column and flame ionization detector are used. 

BidlemanTF. 1988. Atmospheric processes. Wet and dry deposition of organic compounds are controlled by their vapor-particle partitioning. Environ Sci Technol 22(4) 361-367. 

Gossett RW, Brown DA, Young DR. 1983. Predicting the bioaccumulation of organic compounds in marine organisms using octanol/water partition coefficients. Mar Pollut Bull 14 387-392. 

Tewari YB, Miller MM, Wasik SP, et al. 1982. Aqueous solubility and octanol/water partition coefficient of organic compounds at 25.0°C. J Chem Eng Data 27 451-454. 

Sangster, J. Octanol-water partition coefficients of simple organic compounds./. Phys. Chem. Ref. Data 1989, 18.1111-1229. 

L. A. Predicfion of the solubility, activity coefficient and liquid/liquid partition coefficient of organic compounds. QSAR Comb. Sci. 2004, 23, 709-720. 

Rekker, R. E., Mannhold, R., Bijloo, G., De Vries, G Dross, K. The lipophilic behaviour of organic compounds 2. The development of an aliphatic hydrocarbon/ water fragmental system via interconnection with octanol-water partitioning data. Quant. Struct.-Activ. Rel. 1998, 37, 537-548. 

The theory of the process can best be illustrated by considering the operation, frequently carried out in the laboratory, of extracting an organic compound from its aqueous solution with an immiscible solvent. We are concerned here with the distribution law or partition law which, states that if to a system of two liquid layers, made up of two immiscible or slightly miscible components, is added a quantity of a third substance soluble in both layers, then the substance distributes itself between the two layers so that the ratio of the concentration in one solvent to the concentration in the second solvent remains constant at constant temperature. It is assumed that the molecular state of the substance is the same in both solvents. If c and are the concentrations in the layers A and B, then, at constant temperature ... 

Y. Kubota, Ion-Transfer Voltammetry of Organic Compounds at Organic Solvent/Water Interface. Study on Partition of Organic Compounds between Organic Solvent and Water, MS thesis, Fukui Prefectural University, Fukui 1998. 

When both the neutral and the n different charged forms of a compound partition into the organic phase, a minimum of n + 1) titrations with different phase volume ratios is necessary to determine the partition coefficient of each species. For a monoprotic substance, for instance, can be related to pK by an empirical equation [119] ... 

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