Porous membrane enabled mass spectrometry characterization of microfluidic devices

A method for sampling a sample liquid, comprising the steps of:

• flowing the sample liquid in a sample fluid flow channel of a sample fluid conduit, the sample fluid conduit comprising a membrane comprising pores, the membrane preventing the passage of the sample liquid through the pores at a first pressure of the sample liquid in the sample fluid flow channel of the sample fluid conduit;
• flowing solvent composition at a first pressure from the open end of a solvent conduit to contact the membrane;
• establishing a second pressure within the solvent in contact with the membrane through the solvent conduit, the second pressure being lower than the first pressure of the solvent, and wherein at the first pressure the solvent conduit supplies solvent to the membrane and at the second pressure the solvent conduit removes solvent from the membrane;
• drawing sample liquid through the pores of the membrane by the pressure differential of the first pressure of the sample fluid, and the second pressure of the solvent, wherein the extracted sample liquid is combined with the flowing solvent composition and flows into the open end of the solvent conduit;
• and,
• removing the combined extracted sample liquid and solvent composition.