scientificprotocols authored over 7 years ago

  1. Freeze cotton leaves sample at -70 C in a deep freezer.
  2. Transport the sample in an ice chest box.
  3. Check to see that drain plug is closed (left side of condenser) and be sure that switch is off and ballast open.
  4. Turn on bottom switch of the condenser.
  5. Turn on top switches of chamber and set "shelf temperature control" to -400 or -50 C. Then, wait for chamber temperature to drop to set level (it usually takes 1 to 3 hr).
  6. Turn on bottom switch.
  7. Place the frozen samples on trays. Arrange in even layers. Placing second layer of tubes in bottom 2 trays is OK). It may be fun to place the probes into samples to watch the changing temperature.
  8. Close the chamber and wait for 1 to 2 minutes till the samples and chamber temperature equalize. During this time, ice crystals will coat metal parts of the chamber.
  9. Turn on switch and close ballast, and wait for vacuum to reach <100 mT (about 5 to 10 min). In the mean time, condenser temperature should be at least -40 C.
  10. Set "shelf temperature control" to -20 C and let run for 3 hr at least or overnight.
  11. Check the condenser periodically to be sure that the coil has not collected enough ice to lug it up (rarely a problem on a fresh run).
  12. After the run is complete, turn off switch and open ballast.
  13. Turn on and turn off vacuum switches simultaneously.
  14. Remove the samples and turn off top switches.
  15. Turn off switch.
  16. Close the cap of samples tightly immediately.
  17. Place samples in dry, air tight environment as soon as possible and store out of direct sunlight.


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