5.0 g NPH and 200 mL solution (0.5% CPB) were added into one 500 mL conical flask. Then the mixtures were shaken by an orbital shaker at 100 rpm at room temperature (303 K) for 24 h. MPH was separated from the mixtures and washed with distilled water several times for the removal of superficially retained CPB. Finally, MPH was dried at 333 K overnight and stored in an airtight glass bottle.