Method and apparatus to characterize pressurized liquid sample
A method and apparatus for measuring the physical properties of a drug formulation suspended in a pressurized liquid propellant and a system to enable such measurements is disclosed. Drug formulations suspended in pressurized liquid propellant used in Pressurized Metered Dose Inhalers (pMDIs) are propelled in their native liquid state into an analytical instrument with a measurement cell capable of withstanding the pressure required to retain the sample in liquid form by employing a device to rapidly release the contents of the pMDI canister into the measurement instrument wherein the sample's electrophoretic mobility and size may be determined by MP-PALS or other techniques. A series of valves permits the maintenance of the high pressure in the system. Once the measurements are made, the pressurized liquid is allowed to pass to waste or another analytical instrument by opening an exit valve.
1. An apparatus comprising:
an inlet valve;
inlet tubing connecting the inlet valve to a measurement cell,
wherein the inlet valve is located upstream of the measurement cell;
an outlet valve,
wherein the outlet valve is located downstream of the measurement cell;
outlet tubing connecting the measurement cell to the outlet valve; and
a rapid release adapter,
wherein an outlet of the rapid release adapter is connected to an inlet port of the inlet valve,
wherein an inlet port of the rapid release adapter is configured to be connected to a canister containing a liquid sample maintained in a liquid state by a pressure in the canister, and
wherein the rapid release adapter is configured to release the liquid sample from the canister into the inlet valve and the inlet tubing, thereby releasing the liquid sample into the measurement cell; and
wherein the measurement cell is configured to measure physical properties of the liquid sample in the measurement cell,
wherein the liquid sample is maintained in a liquid state while the measurement cell measures the physical properties.
2. The apparatus of claim 1 wherein the measurement cell is an optical measurement cell.
3. The apparatus of claim 1 wherein the measurement cell is an element of an electrophoretic mobility detector.
4. The apparatus of claim 2 wherein the measurement cell is an element of a fluorescence detector.
5. The apparatus of claim 2 wherein the measurement cell is an element of a UV absorption detector.
6. The apparatus of claim 2 wherein the measurement cell is an element of a light scattering detector.
7. The apparatus of claim 6 wherein the light scattering detector is configured to measure dynamic light scattering.
8. The apparatus of claim 6 wherein the measurement cell is an element of a multiangle light scattering detector.
9. The apparatus of claim 3 wherein the electrophoretic mobility detector is an MP-PALS instrument.
10. The apparatus of claim 1 wherein the inlet valve is a check valve configured to permit the liquid sample to flow into the measurement cell and configured to prevent the liquid sample to flow away from the measurement cell.
11. The apparatus of claim 1 wherein the outlet valve comprises
a first port connected to the measurement cell, and
a second port connected to outlet flow tubing.
12. The apparatus of claim 1 wherein the outlet valve comprises
a first port connected by tubing to the measurement cell, and
a second port connected to a syringe configured to evacuate atmosphere contained within the measurement cell and dead volume between the inlet valve and the outlet valve.
13. The apparatus of claim 1 wherein the outlet valve is a three-way valve comprising
a first port connected by tubing to the measurement cell,
a second port connected to a waste line, and
a third port connected to a syringe configured to evacuate atmosphere contained within the measurement cell and dead volume between the inlet valve and the outlet valve.