Recrystallization methods for MALDI matrices

Method 1:

Re-crystallization in 70% MeCN/30% water.

1. Heat a saturated solution of the matrix in 70% MeCN/30% water until boiling.
2. Carefully boil until solid dissolves completely.
3. Cool to room temp, then on ice - precipitate should form.
4. Filter precipitate.

Method 2:

Protocol for re-crystallization of alpha-cyano-4-hyrdoxy-cinnamic acid

1. To 100mg of alpha-cyano-4-hydroxy-cinnamic acid, add 10ml of water
2. Add ammonium hydroxide until most of acid dissolves.
3. Slowly add concentrated HCl to the solution until a large amount of
   the acid has precipitated (about pH 2).
4. Remove the precipitate by centrifugation or filtering.
5. Wash the precipitate several times with 0.1M HCl.
6. Dry matrix and store at -20 C in the dark.