Dialyse

Dialysis separates desired analyte ions or molecules from unwanted molecules, or 'interferents', by allowing the sample solution to diffuse through a semipermeable membrane inserted between two miscible liquids.

The membrane is made of cellulose acetate or cellulose nitrate, with pores ranging from 1 to 5 nanometers in diameter. As a result, only interferents smaller than the cut-off size of the membrane diffuse through it.

In this technique, the sample is placed in a dialysis bag, which is then sealed and immersed in a container of a solution, known as the dialysate, that contains a different concentration of the same interferent.

The difference in concentration creates a concentration gradient, allowing smaller inorganic ions and organic molecules to selectively permeate from high- to low-concentration areas until equilibrium is reached, while larger analyte molecules remain in the original solution.

Although dialysis is usually a slow process, the rate of molecular diffusion can be increased by heating the solution or reducing the membrane thickness.