Octanol-water partition ratio

The best known CE buffer ingredient is sodium dodecyl sulfate (SDS) proposed by Terabe [10,11]. SDS forms micelles and the separation of neutral analytes is achieved by their partitioning between the buffer and the SDS micelles, that is, by their hydrophobicity. This is the basis of MEKC and the mobility of analytes correlates linearly well with logP values, where P is the octanol/water partition ratio. Many other buffer ingredients have been proposed. Most of them implement hydrophobic interactions between the analytes and the buffer ingredients but also ciral selectors have been used as well as various affinity probes. Interest in the ILs used as buffer additives in capillary electromigration methods is due to the fact that they could provide an alternative separation mechanism to two currently implemented mechanisms in CE which are based either on the charge to mass ratio or on the hydrophobicity of the analytes. 

Octanol-Water Partition Ratios for a Selection of Surfactants. 

Hendriks JA, van Der Linde A, Cornelissen G, Sijm DTHM. 2001. The power of size. 1. Rate constants and equilibrium ratios for accumulation of organic substances related to octanol-water partition ratio and species weight. Environ Toxicol Chem 20 1399-1420. 

Umland, J.B. (1983) The determination of 1-octanol/water partition ratios An organic chemistry laboratory experiment. J. Chem. Ed. 60(12), 1081. 

It should be noted that the minimum data set, namely molecular mass, Henry coefficient, the octanol/water partitioning ratio and the acid-base dissociation constant, is the same for all environmental fate submodels. 

Once the composition of each equiHbrium phase is known, infinite dilution activity coefficients for a third component ia each phase can then be calculated. The octanol—water partition coefficient is directly proportional to the ratio of the infinite dilution activity coefficients for a third component distributed between the water-rich and octanol-rich phases (5,24). The primary drawback to the activity coefficient approach to estimation is the difficulty of the calculations involved, particularly when the activity coefficient model is complex. 

Swann R, Laskowski D, McCAll P, et al. 1983. A rapid method for the estimation of the environmental parameters octanol/water partition coefficient, soil sorption constant, water to air ratio, and water solubility. Residue Rev 85 18-28. 

Octanol-Water Partition Coefficient (Kq )—The equilibrium ratio of the concentrations of a chemical in TT-octanol and water, in dilute solution. 

The Rvalues are partition coefficients. The assumption that these are real constants Is seldom completely true, of course, because equilibrium Is rarely achieved and because the equilibrium ratios generally are not the same for all concentration levels. Moreover, It Is difficult to find the needed Information, and one must often accept a single literature value as typical of a given Intermedia transfer. When the organic content of the soli Is known or can be accurately estimated, one can usually derive Kgw from a compound s aqueous solubility, S, or Its octanol/water partition coefficient, KQW (14) Values of Kpa, namely "bloconcentratlon factors" between feed and meat animals (15,16), can also be derived from S or KQW. Bloconcentratlon factors between water and fish are well documented (14) A considerable weakness exists In our perception of the proper estimates to use for partition coefficients between soli and edible crop materials. Thus, at one time, two of the present authors used a default value of Kgp = 1 for munitions compounds that are neither very soluble In water nor very Insoluble (4) at another time, a value of was assumed for compounds with very low values of Ksw, l.e., polybromoblphenyls (6). 

Sutton. C., Calder, J.A. (1975) Solubility of alkylbenzenes in distilled water and seawater at 25°C. J. Chem Eng. Data 20, 320-322. Swann, R.L., Laskowski, D.A., McCall, P.J., Vender Kuy, K., Dishburger, J.J. (1983) A rapid method for the estimation of the environmental parameters octanol/water partition coefficient, soil sorption constant, water to air ratio, and water solubility. Res. Rev. 85, 17-28. 

Once estrogens and progestagens have reached the waterways, a series of processes, such as, photolysis, biodegradation, and sorption to bed-sediments, can contribute to their elimination from the environmental water. Given the relatively low polarity of these compounds, with octanol-water partition coefficients mostly between 103 and 105, sorption to bed-sediments appears to be a likely process. Kd values calculated for estriol, norethindrone, and progesterone in a Spanish river (479,128, and 204, respectively) as the ratio between the sediment concentration (ng kg-1) and the water concentration (ng L 1) indicate that, in fact, these compounds exhibit a general tendency to accumulate in sediments. 

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