CWU Chemistry Laboratory Specific Standard Operating Procedure
SOP for: (check one)
Process
Hazardous Chemical
Hazard Class of Chemicals
Name of Procedure: Freeze-Pump-Thaw Degassing of Liquids
Applies to Lab (name): Chamberland Research Group
SCI Room #: 313
Prepared By: James Siegenthaler, Stephen Chamberland
Date: 9/5/12
Revision: 9/5/12
Special Notifications:
The freeze-pump-thaw technique is used to remove dissolved gasses (removal of oxygen is usually desired) from
organic solvents and solutions.
Hazard Description:
The glass flask may shatter, so ensure that all glassware that will be cooled or evacuated has no visible cracks or star
cracks. Liquid nitrogen is used, so consult the SOP "Using liquid nitrogen” before doing this procedure. High vacuum is
also used, so consult the SOPs "Using the high vacuum pump” and “Using the double manifold” before doing this
procedure if questions arise.
Protective Equipment:
- Lab coat
- Protective wrap-around goggles
- Chemically resistant nitrile gloves
- Long pants
- Close-toed shoes
Engineering Controls:
All procedures must be conducted inside a well-ventilated chemical fume hood behind a blast shield. Before initializing
the vacuum, clear the fume hood of any unnecessary equipment or chemicals. Once the process has begun, close the
fume hood sash as low as possible in case of an explosion. Identify a clear path to the chemical safety shower or fire
extinguisher in case of an emergency.
Special Handling or Storage Requirements:
This procedure utilizes cryogenic chemicals; review “Handling Cryogenic Liquids” and “Using liquid nitrogen” SOPs
before conducting this procedure.
Spill Response Procedure:
Consult the SDS of the chemical being utilized prior to usage.
Decontamination/Waste Disposal:
Consult the SDS of chemical being utilized prior to usage. If spilled chemical has gotten onto clothing, remove
immediately and dispose of as hazardous waste. If spilled chemical has gotten onto exposed skin, wash thoroughly
under warm water for at least fifteen minutes. If a serious spill has occurred, consult a physician.
Special Emergency Procedures:
The shattering of the vessel is the most likely accident during this process. If this were to happen, be prepared with the
correct response if the glass and liquid were to spill. If such shattering were to occur behind the blast shield, turn off the
vacuum line, evacuate nearby personal and clean the chemical spill and glass. If a hazardous chemical has left the
hood, identify the correct procedure for cleanup, and then alert the PI and EH&S.
Procedure may be performed after normal working hours (M-F, 8-5)?
Procedure may be left unattended?
Yes
Yes
No
No
Step by Step Procedure:
1. Clear the fume hood of any clutter or unnecessary lab equipment or chemicals.
2. Wear the appropriate PPE detailed in the above list and ensure it is in good working order.
3. Check the manifold and all glass for cracks, leaks or other potential hazards, ensure that hoses are connected
securely, that joints are well greased, and that the gas line is functioning properly.
4. Place the solvent or solution into a Schlenk flask or round-bottomed flask (that has been flame dried first – only Dr.
Chamberland can do this procedure) and connect this flask to the manifold tubing with a glass tubing adapter that
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CWU Chemistry Laboratory Specific Standard Operating Procedure
5.
6.
7.
8.
9.
10.
11.
12.
has a stopcock. Secure this flask by attaching a metal three-prong clamp to its neck and to the sturdy metal bars in
the fume hood. Do not perform this procedure with a rubber septum on the flask with nitrogen introduced from the
manifold through a needle. Make sure that the stopcock is closed and that the flask is filled no more than 50% of
the volume. Overfilled flasks frequently shatter during this process.
Having been flame dried, the flask should be connected to the nitrogen gas / high vacuum pump dual manifold with
the stopcock attached to the flask open to nitrogen.
Turn on the and vacuum, but do not allow either the vacuum to be opened to the flask. Consult the SOPs "Using the
high vacuum pump” and “Using the double manifold” to familiarize how to use the manifold and vacuum pump
correctly. The solvent trap for the vacuum pump should be cooled with liquid nitrogen. Consult the SOPs “Handling
Cryogenic Liquids” and “Using liquid nitrogen” if you have questions.
While the flask is under nitrogen gas, cool/freeze the liquid in the flask by slowly submerging the flask (up to the
neck) into a Dewar containing liquid nitrogen. The glassware will initially cause the liquid nitrogen to bubble, but
bubbling will cease as the flask cools.
Once the contents are frozen, open the stopcock on the manifold to vacuum and pump for 5-10 minutes. The space
above and within the frozen liquid should be completely evacuated.
Close the stopcock at the top of the flask while leaving the stopcock on the manifold open to vacuum.
Remove the flask from the cold bath and allow it to thaw slowly at first, and then insert it (up to the neck only) into a
warm (room temperature or just above room temperature) water bath until the solution melts. You may see gas
bubbles evolve from the solution. Try not to disturb the liquid. Note: Letting the solvent thaw by itself or using a
container of water that melts only the bottom of the frozen solvent may cause the vessel to break. Do not use direct
heat to thaw!
Remove the flask from the warm water bath and repeat steps 7 – 10 at least 3 times (4 cycles).
After warming the flask after the fourth FPT cycle, backfill the flask with nitrogen gas. The solvent or solution is
degassed and ready for use.
Approved By (PI) : Stephen Chamberland, Ph.D.
Date: 9/5/12
PI Signature: ___________________________________________________
Date: ______________
EH&S Signature: ________________________________________________
Date: ______________
PRINTED 2/9/2016
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KUHLKEN, CHEMISTRY DEPARTMENT, CENTRAL WASHINGTON UNIVERSITY
DOCUMENT1