Method of characterization of release of poorly soluble materials and uptake in complex liquids

A method for determining the quantity of a diffusible agent that is exchanged between two media, comprising:

• a) providing a first exchange chamber comprising a section of relatively highly permeable membrane through which a diffusible agent is to be transferred and attached to and positioned between an inlet to a single, common reservoir or source of flow medium and an outlet to said reservoir, where the inlet and outlet materials are relatively impermeable to said diffusible agent;
• b) providing a second exchange chamber comprising a section of relatively highly permeable membrane through which a diffusible agent is to be transferred and attached to and positioned between an inlet to said common reservoir or source of flow medium and an outlet to said reservoir, where the inlet and outlet materials are relatively impermeable to said diffusible agent;
• c) putting said first exchange chamber in contact with a first external medium by immersing it sufficiently in said first external medium so exchange of said diffusible agent can occur between said flow medium and said first external medium;
• d) putting said second exchange chamber in contact with a second external medium by immersing it sufficiently in said first external medium so exchange of said diffusible agent can occur between said flow medium and said second external medium;
• e) simultaneously perfusing a known quantity of flow medium from said common reservoir, through said relatively impermeable tubing and said first exchange chamber, and back to said common reservoir at a controlled flow rate, and perfusing a known quantity of flow medium from said common reservoir, through said relatively impermeable tubing and said second exchange chamber, and back to said common reservoir at a controlled flow rate;
• f) at a known time, withdrawing a sample of known volume of said flow medium from said common reservoir, and optionally replacing said withdrawn sample by adding an equal volume of a replacement liquid of known composition to said common reservoir;
• g) determining the mass of said diffusible agent in said flow medium sample, and determining the mass exchanged between said flow medium and said first external medium and said second external medium during step (e);
• h) optionally continuing step (e) and repeating steps (f) and (g) for a selected time or number of samples.

A method for determining the quantity of a diffusible agent that is exchanged between two media, comprising:

• a) providing at least one exchange chamber comprising a section of relatively highly permeable membrane through which a diffusible agent is to be transferred, and attached and positioned between a first segment of tubing that can accept flow medium from or supply it to a first reservoir, and a second segment of tubing that can accept flow medium from or supply it to a second reservoir, where said first and said second segments of tubing are relatively impermeable to said diffusible agent;
• b) putting said exchange chamber in contact with an external medium by immersing it sufficiently in the external medium so exchange of said diffusible agent can occur between the flow medium and external medium;
• c) perfusing a known quantity of a flow medium from the first reservoir, through said relatively impermeable tubing and said exchange chamber, and to the second reservoir at a controlled flow rate;
• d) at a known time, withdrawing a sample of flow medium from either reservoir, determining the mass of said diffusible agent in said flow medium sample, and optionally replacing said withdrawn sample by adding an equal volume of a replacement liquid of known composition to said reservoir from which said sample was taken;
• e) determining the mass of said diffusible agent in said flow medium sample, and determining the mass exchanged between said flow medium and said external medium during step (c);
• f) optionally reversing the flow direction of the flow medium, perfusing said flow medium from the second reservoir, through impermeable tubing and said exchange chamber, and to said first reservoir at a controlled flow rate that may be the same or different from the flow rate in step (c);
• g) at a known time, withdrawing a sample of flow medium from either reservoir, determining the mass of said diffusible agent in said flow medium sample, and optionally replacing said withdrawn sample by adding an equal volume of a replacement liquid of known composition to said reservoir from which said sample was taken;
• h) optionally, repeating steps (c) through (f) using the same or different flow rates, for a selected time or number of samples.