Determination using partition coefficients

The determination of partition coefficients using liposomes as a lipid phase require that the sample be equilibrated with a suspension of liposomes, followed by a separation procedure, before the sample is quantitated in the fraction free of the lipid component. 

Miyake, K. Kitaura, F. Mizuno, N., Phosphatidylcholine-coated silica as a useful stationary phase for high-performance liquid chromatographic determination of partition coefficients between octanol and water, J. Chromatogr. 389, 47-56 (1987). 

Fujisawa S, Masuhara E. 1981. Determination of partition coefficients of acrylates, methacrylates, and vinyl monomers using high performance liquid chromatography (HPLC). J Biomed Mater Res 15 787- 793. 

Renberg, L.O., Sundstrom, S.G., and Rosen-Olofsson, A.-C. The determination of partition coefficients of organic compounds in technical products and waste waters for the estimation of their bioaccumulation potential using reversed phase thin layer chromatography, Toxicol. Environ. Chem., 10 333-349, 1985. 

The two-phase titration was first described in 1963 (19) as a means to simultaneously determine a partition coefficient and pKa. Several variations have appeared since (20-24), but none has seemed to gain favor. I like the simplified approach of Clarke (25,26) who uses the method to determine partition coefficients after separately determining (or knowing) the pKa. 

Bard, B., Carrupt, P.A. and Martel, S. (2009) Determination of partition coefficients of basic drugs using hydrophilic interaction chromatography. Journal of Medicinal Chemistry, 52, 3416-3419. 

A system similar to the one described above was used for determination of partition coefficients. A FIA system with segmented flow was devised so that the partitioning of a drug between aqueous buffer and chloroform could be measured. The aqueous and organic phases were separated using a phase separator. The system could be set up to measure the concentration of the drug in either the organic or the aqueous phase. Such a system enables rapid repeat determinations of partition coefficient at various pH values with minimal sample consumption." ... 

A Physical Research Technique. It may be used to investigate various parameters of a system, for example, determination of partition coefficients, thermodynamic functions, and adsorption isotherms. 

Hu, J., Leng, X.-F. (1992) Determination of partition coefficients for some pesticides by using reversed-phase high performance liquid chromatography (HPLC). Sepu 10, 344-346. 

In the case of HOCs, equations are used to determine the partitioning coefficient between organic carbon and water (K0c), based on aqueous solubility (5) or an octanol/water partition coefficient (Kov/). 

To recap, first one needs to determine the partition coefficients for each of the analytes on each of the two liquid phases—each chosen because it is effective in separating most of the sample analytes when used alone. Second, one plots these K values versus < > by using the two K values for each analyte at 4>a- = 0 and < >a- = 1.0 and joining these two points with a straight line. Then, the window diagram is drawn using <(> values calculated from Eq. (10) at various a values. 

Several methods are used to determine the partition coefficient of solutes between water and liposomes. 

The ratio of organic to aqueous phase is expressed as r, PB is the partition coefficient of the unionised, PBH+ is the partition coefficient of the protonated analyte. Using this approach depending on the nature of the analyte, several titrations (for monoprotic compounds at least two experiments) using different ratios of lipid to water phase have to be carried out in order to determine the partition coefficients of the solute. The result is a partition coefficient-pH profile for the compound and its distinct ionisation states. 

Effect of Tween 80 on TFMS tt Values. Table VI lists octanol/water partitioning data for the 15 substituted TFMS compounds used in this study. Logarithms of the partition coefficients obtained both in the absence (log Px) and presence (log Px) of 0.1% (w/v) Tween 80 are given. (Procedures for determining the partition coefficients Px and Px have been outlined in the Experimental section.) tt, tt, and w" values in Table VI were calculated according to the following relationships ... 

Most of the static headspace methods determine the partition coefficient by quantifying volatile concentration above a sample by gas-chromatography. The vapour phase calibration method (VPC) uses an external vapour standard for calibration. One must assure that the pure component is completely vaporized before injection. A widely employed alternative is the Liquid calibration static headspace (LC-SH) method (YoiWey et al. 1991 Nedjma 1997). A third approach uses HS-SPME. SPME may be used to determine partition coefficients if short sampling times are applied the process must only sample the headspace and not disrupt the equilibrium (Jung and Ebeler 2003). This method has become very popular to study the effect of wine macromolecules on the liquid-vapor equilibrium, (Whiton and Zoecklein 2000 Escalona et al. 2002 Hartmann et al. 2002 Aronson and Ebeler 2004). 

Davis, S.S., Elson, G., Tomlinson, E., Harrison, G., Dearden, J.C. (1976) The rapid determination of partition coefficient data using a continuous solvent extraction system. (AKUFVE). Chem. Ind. (London), 16, 677-683. de Kreuk, J.F., Hanstveit, A.O. (1981) Determination of the biodegradabUity of the organic fraction of chemical wastes. Chemosphere 10, 561-575. 

The more traditional approach is to use the chromatographic technique for the concentration determination necessary to derive physico-chemical properties for example, measuring the equilibrium concentration of compounds in a saturated solution for solubility measurements, or measuring the distribution concentration in two immiscible solvents for the determination of partition coefficients. Both approaches can be used for lipophilicity determinations and will be fully discussed in this chapter. 

The composition of the mobile phase also has an influence on the partition coefficients of inorganic substances and the separation efficiency. Concentrations of the mobile-phase constituents should provide partition coefficient values needed for the enrichment or separation of components under investigation. If a step-elution mode is used, partition coefficients higher than 10 and less than 0.1 are favorable for the enrichment of components into the stationary phase and their recovery into the mobile phase, respectively. Chemical kinetics factors may also play an important role in the separation of inorganic species by CCC [9]. It has been shown that the values of mass-transfer coefficients determine the... 

Cabala, R., Svobodova, J., Feltl, L. and Tichy, M. (1992). Direct Determination of Partition Coefficients of Volatile Liquids Between Oil and Gas by Gas Chromatography and Its Use in QSAR Analysis. Chromatographia, 34,601-606. 

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