Cold Traps Information
Cold traps protect vacuum pumps from contamination by sublimating or condensing vapors (except permanent gases) in a dedicated device. They also prevent oil vapors from backstreaming from the pump into the system. Cold traps provide vacuum pumps more efficient operation and longer service lives.
As a vacuum pump eliminates gas from a chamber a cold trap condenses or sublimates gases, such as vapor from water or solvents. This prevents the vapors from contaminating the vacuum pump and the airstream, which could lead to malfunctions. Cold traps most commonly collect vapor from applications involving rotating discs or vacuum systems; cold traps can also collect oil vapors from a pump to prevent them from flowing into the chamber. Sometimes cold traps function to purposefully condense materials with the use of temperature monitoring equipment. Cold traps are most frequently implemented to condense gases, but may be used on other types on contamination, including solids.
The trap is often lowered in a Dewar vessel and positioned before the mouth of the vacuum pump to force the airstream through the mechanism. Cold traps maintain a chilled stainless steel or glass surface or well for vapors to condense or sublimate on; glass is preferable when chemical resistance is a concern. These devices utilize an active material such as dry ice or liquid nitrogen or a Peltier element for cooling. The trap is filled after the chamber has been evacuated of most condensable vapors, typically at a pressure of less than one millitorr. Operators can dispose of accumulated frost or liquid, or in the case of a solvent may repurpose it.
Cryogenic cold traps (CCTs) are specifically manufactured for cryogenic applications and are designed to withstand the rapid changes in temperature from processes such as gas chromatography. CCTs are useful for the adsorption of noble gases and the extraction of gasses or adsorption of oxygen isotopes from samples.
Condensate capacity: the quantity of vapor that can be captured
Temperature range: the operational range of the cold trap; determines what chemicals can be condensed or sublimed
Coolant capacity: the quantity of dry ice or liquid nitrogen
Dewar type: the model of flask the cold trap is compatible with
Joints/connections: how the cold trap interfaces with other labware, including vacuum flanges, glass threads, spherical ground joints (with optional o-ring), and conical ground joints
Wire basket: to easily exchange dry ice cold traps in the Dewar flask
Spout: the cold trap has a spout to pour out condensate
Segmented: the cold trap can be disassembled for easy or partial cleaning
Flat bottom: cold trap has a flat base for stability