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Lab Dialysis


The term “Dialysis” which means “loosening from something else" was originally used by Thomas Graham in 1886. It can be defined as “diffusion of molecules across a semi-permeable membrane along a concentration gradient”.

Dialysis has been significantly used as a routine method for desalting and concentration of intricate biomolecules in solution. The conditions of dialysis are controlled or manipulated to produce desired results for a variety of applications, based on Molecular Weight Cut Off (MWCO). Depending upon application, membrane of appropriate pore size is selected.

The dialysis membrane consists of a matrix of cross-linked polymers. Cellulose membranes have the longest history of use in membrane industry and even now are maintaining their top position. Regenerated Cellulose (RC) membranes, owing to their inertness and ruggedness enjoy preference in dialysis (Regenerated celluloseis the cellulose obtained by regenerating ie chemically or physically modifying existing natural cellulose). RC membranes are permeable to both inorganic and organic compounds, show excellent dialysis performance, have high mechanical strength and good chemical compatibility with most solvents, making them suitable for a wide variety of environmental applications.

The rate of transport of molecules across the semipermeable dialysis membrane is a function of:

  1. Molecular shape
  2. Size and weight
  3. Degree of hydration
  4. Ionic charge/polarity
  5. Fluid temperature
  6. Wall-thickness of membrane
  7. Concentration gradient

Advantages of dialysis

  1. Easy Operation
  2. Inexpensive Materials
  3. Mild experimental Conditions
  4. Processing of samples over wide range of volumes possible
  5. Availability of different Membrane Types & MWCO's facilitate use in different applications

General Applications of dialysis

  1. Macromolecular Purification
  2. Protein Concentration
  3. Solute Fractionation
  4. Contaminant Removal
  5. Desalting
  6. Buffer Exchange
  7. Electro-elution

Some innovative applications of dialysis

  1. Enzyme immobilization studies
  2. Purification of ionic liquids
  3. Nanotechnology e.g. studying release profile of drug loaded nano-particles or microspheres
  4. Drug binding studies (in vitro)