I suppose the question is because of concerns about the enantiomer that was just purified interconverting back to a racemate?
I'm also assuming the prep HPLC used water/methanol for a solvent system.
I would keep it cool- evaporate the methanol, followed by freeze-drying to remove the water. The product would be below freezing as the water is removed, and has less energy to interconvert.