Definition of Distribution Law:
The distribution law, also known as Nernst's distribution law, states that when a solute is distributed between two immiscible solvents at a constant temperature, the ratio of its concentrations in the two solvents is constant.
[Solute]A & [Solute]B are the concentrations of the solute in solvents A and B, respectively.
Kd is the distribution coefficient or partition coefficient.
Assumptions:
The solute does not react chemically with any of the solvents.
The solute exists in the same molecular form in both solvents.
The system is at a constant temperature.
The solvents are immiscible.
Limitations of the Distribution Law
Chemical Changes: If the solute reacts chemically or changes state in one of the solvents, the law doesn't apply.
Solvent-Solvent Interaction: Even slight miscibility between solvents can affect the partition coefficient.
Temperature Variations: Changes in temperature can alter the partition coefficient, affecting distribution.
Concentration Dependence: High concentrations can lead to solute saturation or self-interaction, deviating from expected behaviors.
Physical Form Variations: Differences in solute ionization or physical state between solvents can impact distribution.
Applications of the Distribution Law
Drug Design and Pharmacokinetics: Essential for understanding drug distribution across body compartments, impacting dosing and delivery.
Environmental Science: Helps predict the movement of pollutants between phases like water and oil.
Extraction Processes: Guides the selection of solvents for efficient compound extraction in chemical and pharmaceutical industries.
Analytical Chemistry: Basis for solvent choice in liquid-liquid extraction, optimizing separation of analytes.
Food Industry: Influences the formulation by predicting how additives distribute between different phases.