2.5. In vitro release test
Two types of release tests were arranged for the infinite and practical dose. For the infinite dose study, DPH release was determined by dialysis using a cellulose dialysis tube and JPXV dissolution test apparatus (Toyama Sangyo, Osaka). One mL of EL and 10mL of water were placed in a rotation basket covered with a dialysis membrane filter (#36,WakoPureChemical).The release test was done at a rotation speed of 100 rpm, dissolution medium of 900 mL at pH7 phosphate buffer solution. At pre- determined time intervals, 5 mL of medium were removed and fresh medium was added. DPH concentration was determined by absorbance at 218 nm.