At the end of the in vitro permeation experiment,
the residual applied drug level in the skin was also determined by a homogenization method.
After wash, the skin was cut to small pieces
and place into a glass tube containing 2 mL methanol in an ice bath.
The sample was homogenized at 17,800 rpm for 2 min,
and then shaken horizontally for 30 min.
The resulting solution was centrifuged for 10 min at 3100 × g.
The supernatant was determined by HPLC.