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Trituration











Trituration Techniques

Trituration can be defined as the purification of an impure compound by taking advantage of the solubility differences of the compound vs its impurities in a solvent (or solvent mixture). Below are three common trituration techniques.

 

A) Suspend & Filter

  1. Find an appropriate solvent (or solvent mixture). The solvent should be one in which your pdt is sparingly soluble and your impurities are highly soluble.
  2. Suspend your crude pdt in the solvent. Ideally your crude will be a relatively fine solid so that all impurities are exposed to solvent and have the opportunity to dissolve.
  3. Stir the mixture. This can be done by hand or with a stir bar.
  4. Filter the solids. Usually a buchner funnel will be used.
  5. Wash the filter cake with a minimum amount of the same solvent. Using cold solvent for the wash will decrease the loss of pdt during the rinse.

B) Solvent then Anti-Solvent

  1. Dissolve your impure pdt in a minimum amount of solvent in which it has moderate/strong solubility.
  2. While stirring, slowly add an anti-solvent (a solvent in which your pdt has poor solubility) until most solids crash out.
  3. Filter the solids. Usually a buchner funnel will be used.
  4. Wash the filter cake with a minimum amount of solvent. Use about the same solvent mixture/ratio which you ended up with at the end of the antisolvent addition. Using cold solvent for the wash will decrease the loss of pdt during the rinse.

C) Solvent Swap

  1. Dissolve you compound in a mixture of two solvents. One solvent should be a lower boiling solvent in which your compound has good solubility (ex. DCM), the other solvent (anti-solvent) should be a higher boiling solvent in which you compound has poor solubility (ex. EtOH).
  2. Concentrate the mixture on the rotovap until most of the solids have crashed out.
  3. Filter the solids. Usually a buchner funnel will be used.
  4. Wash the filter cake with a minimum amount of solvent. Use a solvent mixture/ratio which is higher in ratio of anti-solvent:solvent than the initial solvent mixture used to dissolve your impure pdt. Using cold solvent for the wash will decrease the loss of pdt during the rinse.