After evaporation to dryness in a vacuum centrifuge, for derivatization 0.5 ml of 2,2,2-trifluoroethanol and cautiously 1 ml of freezing cold (-40°C) trifluoroacetic anhydride were added to the residue.
Afterevaporation to dryness in a vacuum centrifuge, for derivatization 0.5ml of 2,2,2-trifluoroethanol and cautiously 1 ml of freezing cold (-40°C)trifluoroacetic anhydride were added to the residue.