Multiple Stage Experiments
In selected AC experiments, such as those of the 0.5 V
AC protocol, passive and AC transport experiments were
carried out with the same HEM samples. These experiments
were divided into either two or three stages. In the threestage
experiments, stage I was a passive transport experiment.
Stage II was AC iontophoresis experiment on the
same membrane. Stage III was a repeat of the passive
experiment of stage I after stage II. Stages I and III were the
controls in data analyses to minimize the effects of skin-to-skin
variability. In the two-stage experiments, stage III was not
carried out.