Compound distribution in microfluidic devices

A method of analyzing compound distribution in a system, comprising:

• a) providing i) a first system comprising a first microfluidic device comprising a first membrane with pores in a plurality of regions, and ii) a first experimental protocol for use with said first system, said first experimental protocol comprising introducing a compound into said first microfluidic device and taking actions at one or more timepoints;
• b) replacing said first system with a second system, said second system comprising a second microfluidic device comprising a second membrane without pores in at least one region in which said first membrane comprises pores;
• c) modifying said first experimental protocol to generate a modified experimental protocol, wherein said modified experimental protocol comprises introducing said compound into said second microfluidic device and measuring compound concentration at one or more of said timepoints from said first experimental protocol;
• d) performing said modified experimental protocol;
• and
• e) using said measurement of concentration of said compound to analyze compound distribution across said system.