Critical Point Dryer
Critical point drying is commonly used as the final step in the ethanol dehydration of biological samples before they are sputter-coated and imaged using the scanning electron microscope. Critical point drying may also be performed on materials samples, for example those for which air-drying would result in capillary-force-induced collapse of a fragile structure. A sample is brought to the critical point dryer still immersed in 100% ethanol. The chamber is then filled with enough 100% ethanol to completely cover the sample, and the sample is quickly transferred to the chamber. The chamber is then sealed, cooled, and valves are opened to let liquid CO2 in, forcing ethanol out, until liquid CO2 completely replaces the ethanol. At this point the chamber is sealed again and gently heated. Once the chamber pressure exceeds 1072 PSI and the temperature exceeds 31 C, all of the CO2 in the chamber becomes super critical. Above its critical point, the liquid and gas phases of CO2 are in equilibrium, and the CO2 may be slowly drained from the chamber (and the sample) as a gas. Gaseous CO2 leaves the sample without causing the physical destruction one would normally see, for example, when a worm dries out on a sidewalk, as the water in the worm changes phase, from liquid to gas.
|Primary Contact||Mark Bee|
|Features||- Advanced auto-pressure and temperature control|
- 1.25" ID chamber and 1.25" height