The calculation of Kd is concentration on the solids (mg kg–1 dry solid) divided by concentration in the pore water (mg L–1), giving units of L kg–1.
Table of Contents
How do you find the distribution coefficient in chemistry?
What is distribution coefficient Kd?
The parameter known as the partition (or distribution) coefficient (Kd) is one of the most important parameters used in estimating the migration potential of contaminants present in aqueous solutions in contact with surface, subsurface and suspended solids.
What are the methods of measuring distribution coefficient?
A number of methods of measuring distribution coefficients have been developed, including the shake-flask, separating funnel method, reverse-phase HPLC, and pH-metric techniques.
What is the distribution coefficient log D?
LogD is a distribution coefficient widely used to measure the lipophilicity of ionizable compounds, where the partition is a function of the pH. For non-ionizable compounds LogP = LogD throughout pH range, whereas for ionizable compounds LogD takes into account the partition of both ionized and non-ionized forms.
Is distribution coefficient the same as partition coefficient?
The key difference between partition coefficient and distribution coefficient is that the term partition coefficient refers to the concentration of un-ionized chemical species of a compound whereas the term distribution coefficient refers to the concentration of both ionized and un-ionized chemical species of a …
What is Kd soil chemistry?
Soil adsorption coefficient (Kd) measures the amount of chemical substance adsorbed onto soil per amount of water. It is also known as Freundlich solid-water distribution coefficients (Kf).
What is the use of distribution coefficient?
The use of distribution coefficients (log D) for the analysis of structure-activity relationships of ionizable compounds is described. (D is the ratio of the equilibrium concentration of compound in an organic phase to the total concentration of un-ionized and ionized species in the aqueous phase at a given pH.)
What is the formula of distribution ratio?
The Distribution ratio formula is defined as the ratio of the total concentration of solute in the same solvent but the phases of the solvent are different and is represented as D = (Co/Caq) or Distribution Ratio = (Concentration in organic phase/Concentration in aqueous phase).
How does pH affect distribution coefficient?
The distribution constant is pH dependent and the term logD is used to reflect the pH dependent lipophilicity of a drug. The lower the pH of an aqueous solution, the further to the left is the position of equilibrium, i.e. increasing [drug molecule]water and decreasing [drug ion]water.
Is logD the same as logP?
LogD describes the distribution of all forms of the compound at a specific pH. Un-ionized, ionized, ionized at some other position—all species go into the equation. Unlike logP, which is pH-independent, logD changes with pH as the fraction of each species shifts.
What is the relationship between logD and pH?
Log D is thus pH dependent, hence the one must specify the pH at which the log D was measured. Of particular interest is the log D at pH = 7.4 (the physiological pH of blood serum). Applications like Marvin allow the user to calculate the logD but also display the pH distribution profile, as shown below for Warfarin.
How is logP value calculated?
logP calculations are based on a pool of fragments predefined in the calculator. This set is based on the data set in references 1. Every fragment is assigned a unique name and a value. The logP value of a molecule is the sum of the fragment values present in the molecule.
What is KD in organic chemistry?
The ratio of solubilities in the two solvents is called the distribution coefficient, KD = C1/C2, which is an equilibrium constant with a characteristic value for any compound at a given temperature.
How is KD adsorption calculated?
The best approach is to use Kd = qe/ce.
What is Kd and Koc?
Adsorption-desorption distribution (Kd) and organic carbon-water partition (KOC) coefficients.
What is distribution ratio in chemistry?
distribution ratio in American English Chemistry. the ratio of concentrations of a solute distributed between two immiscible solvents in contact with each other, as iodine in water and chloroform.
What does a large distribution coefficient mean?
What is the difference between solubility and partition coefficient?
The difference between the two is that solubility measures the amount of solute that can be dissolved in one solvent, while partition coefficient measures the ability of the solute to go into two immiscible phases.
What does LogD mean?
Definition: A measure of the preference of a compound to dissolve in either water or an organic solvent (such as octanol).
What does a high LogP mean?
LogP gives you an indication of how well the molecule will partition into the organic elution solvent. The higher the logP, the more likely the compound will partition from the SLE phase into the organic elution solvent like dichloromethane, ethyl acetate or MTBE.
What is a good LogD value?
According to this rule, the successful drug candidate should possess LogP value not greater than 5. LogD is a distribution coefficient widely used to measure the lipophilicity of ionizable compounds, where the partition is a function of the pH.
What is LogP in Lipinski rule?
LogP is an important component of Lipinski’s Rule of 5 recommendations which predicts the drug-likeness of a new synthetic compound. According to Lipinski’s Rule of 5, an oral drug should have a LogP value <5, ideally between 1.35-1.8 for good oral and intestinal absorption.
Is High LogP lipophilic?
High lipophilicity (logP>5) often contributes to high metabolic turnover, low solubility, and poor oral absorption. In addition, highly lipophilic compounds tend to bind to hydrophobic targets other than the desired target, and, therefore, there is an increased risk of promiscuity and toxicity.
How do you calculate the LogP of a molecule?
We proposed a simple equation based on the number of carbon atoms, NC, and the number of hetero atoms, NHET: log P = 1.46(±0.02) + 0.11(±0.001) NC−0.11(±0.001) NHET.