Determination of partition coefficient

The main aim of this study was to determine the logarithm of partition coefficient values by the novel and simple thin layer chromatography method. The experimental data revealed a linear relationship between and the concentration of the organic modifier acetonitrile. The value decreases with the increase in concentration of modifier in the mobile phase.

Determination of partition coefficient

Hence the hydrophobicity of a compound as measured by its distribution coefficient is a major determinant of how drug-like it is.

Partition Coefficient by DrGergens

More specifically, for a drug to be orally absorbed, it normally must first pass through lipid bilayers in the intestinal epithelium a process known as transcellular transport.

For efficient transport, the drug must be hydrophobic enough to partition into the lipid bilayer, but not so hydrophobic, that once it is in the bilayer, it will not partition out again. Pharmacodynamics[ edit ] In the context of pharmacodynamics what a drug does to the bodythe hydrophobic effect is the major driving force for the binding of drugs to their receptor targets.

In some cases the metabolites may be chemically reactive. Hence it is advisable to make the drug as hydrophilic as possible while it still retains adequate binding affinity to the therapeutic protein target.

Agrochemical research[ edit ] Hydrophobic insecticides and herbicides tend to be more active. Hydrophobic agrochemicals in general have longer half lives and therefore display increased risk of adverse environmental impact. It is a critical parameter for purification using zone meltingand determines how effectively an impurity can be removed using directional solidificationdescribed Determination of partition coefficient the Scheil equation.

The log P of a solute can be determined by correlating its retention time with similar compounds with known log P values. Moreover, Determination of partition coefficient the value of log P is determined by linear regressionseveral compounds with similar structures must have known log P values, and extrapolation from one chemical class to another—applying a regression equation derived from one chemical class to a second one—may not be reliable, since each chemical classes will have its characteristic regression parameters.

The method does, however, require the separate determination of the pKa value s of the substance. Electrochemical[ edit ] Polarized liquid interfaces have been used to examine the thermodynamics and kinetics of the transfer of charged species from one phase to another.

Two main methods exist. Here a reaction at a triple interface between a conductive solid, droplets of a redox active liquid phase and an electrolyte solution have been used to determine the energy required to transfer a charged species across the interface.

For example, tens of thousands of industrially manufactured chemicals are in common use, but only a small fraction have undergone rigorous toxicological evaluation.

Hence there is a need to prioritize the remainder for testing. QSAR equations which in turn are based on calculated partition coefficients can be used to provide toxicity estimates.

Other prediction methods rely on other experimental measurements such as solubility. The methods also differ in accuracy and whether they can be applied to all molecules, or only ones similar to molecules already studied.

Atom-based Standard approaches of this type, using atomic contributions, have been named by those formulating them with a prefix letter: A conventional method for predicting log P through this type of method is to parameterize the distribution coefficient contributions of various atoms to the over-all molecular partition coefficient, which produces a parametric model.

This parametric model can be estimated using constrained least-squares estimationusing a training set of compounds with experimentally measured partition coefficients.

Partition coefficient

While this method is generally the least accurate, the advantage is that it is the most general, being able to provide at least a rough estimate for a wide variety of molecules.

It has been shown that the log P of a compound can be determined by the sum of its non-overlapping molecular fragments defined as one or more atoms covalently bound to each other within the molecule.

Fragmentary log P values have been determined in a statistical method analogous to the atomic methods least squares fitting to a training set.

In addition, Hammett type corrections are included to account of electronic and steric effects.

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This method in general gives better results than atomic based methods, but cannot be used to predict partition coefficients for molecules containing unusual functional groups for which the method has not yet been parameterized most likely because of the lack of experimental data for molecules containing such functional groups.

Molecule mining approaches apply a similarity matrix based prediction or an automatic fragmentation scheme into molecular substructures. Furthermore, there exist also approaches using maximum common subgraph searches or molecule kernels.

Log D from log P and pKa For cases where the molecule is un-ionized:Calculations: Partition Coefficient for Water Kg organic layer / grams water layer K = Partition Coefficient for Bicarbonate Kg organic layer /g bicarbonate layer K Conclusion: From this lab, we have learned that the partition coefficient for benzoic acid can differ greatly.

n-Octanol/water partition coefficient (K ow) is defined as the ratio of the molar concentrations of a chemical in n-octanol and water, in dilute solution.


The coefficient K ow is a constant for a given chemical at a given temperature. The partition coefficient of the test substance is obtained by interpolation of the calculated capacity factor on the calibration graph. For very low and very high partition coefficients extrapolation is . To determination the partition coefficient of ethanoic acid between water and butanol.

Procedure 1.

Determination of partition coefficient

The room temperature was recorded. 2. 15cm3 of the given aqueous ethanoic acid and 15cm3 of butanol were poured into a cm3 separating funnel, using suitable apparatus. The funnel was stoppered and was shook vigorously for 1 to 2 minutes.

To Determination the Partition Coefficient of Ethanoic Acid Between Water and ButanOl. Aim To determination the partition coefficient of ethanoic acid between water and butanol.

Procedure 1. The room temperature was recorded. PC - Partition Coefficient Course Activity.


Below are tutorials for learning and reviewing some simple basic ideas about extraction, a physical separation technique their distribution ratios under various pH.

Coefficient of determination | Revolvy