Equilibrium Dialysis
Definition
Variant in which the drug is allowed to redistribute across the membrane until the unbound concentration on both sides is equal. The classical reference method for measuring plasma protein binding and free drug fraction.
- Measures
- Plasma protein binding, free drug fraction
- Method
- Passive diffusion across a membrane to equilibrium
- Status
- Classical reference method
Common questions
Why is equilibrium dialysis considered the reference method rather than ultrafiltration for protein binding studies?+
It allows the system to reach true thermodynamic equilibrium without the physical stresses of filtration, such as membrane binding or volume shift, which can bias the free fraction measured by faster alternative methods.
What limits equilibrium dialysis for routine forensic toxicology casework?+
It is comparatively slow, often taking hours to reach equilibrium, which makes it less practical than faster screening approaches when a case needs quick turnaround rather than precise protein-binding data.
Related terms
- Conway Microdiffusion Cell
- A two-compartment glass or ceramic dish with a central well and an outer ring, sealed at the rim. The poison is released...
- Dialysis
- Separation of small molecules from large ones across a semipermeable cellulose membrane. In forensic toxicology, used for clean-up of blood and plasma...
- MWCO
- Molecular weight cut-off, the nominal size above which the membrane retains solutes. Forensic dialysis tubing typically uses 12 to 14 kDa MWCO,...
- Simple Distillation
- Heating an aqueous sample in a round-bottom flask and collecting the condensed vapour. Used for volatiles that boil below 100 degrees C...
- Steam Distillation
- Passing live steam through a sample so that volatile organic compounds co-distil with water at a temperature below their own boiling point....