2,4 DNPH was recrystallized prior to use. Recrystallization was
performed by dissolving 10 g of 2,4 DNPH in 100 mL in hot analytical
grade acetonitrile to form a saturated solution. After complete
dissolution, the solution was cooled to room temperature, capped
in a brown bottle and stored overnight at 4 C for crystallization.
The crystals were collected by vacuum filtration. 150 mg of 2,4
DNPH crystals were accurately weighed, dissolved in 49.5 mL of
acetonitrile and mixed with 0.5 mL of phosphoric acid (85%).