sublimation of frozen aliquots on storage (View forum version)



microphobe

Posted 11 January 2012 - 09:22 PM

Anyone got any tips to avoid this? We typically aliquot antibodies in 10ul lots at -20 to avoid repeated freeze-thaws, but for some of my aliquots the ice has sublimed up the walls and lid of my eppies leaving the sample lyophilized (and dead) after about 18 months of storage.

akhshik

Posted 31 January 2012 - 02:22 AM

you could thaw them slowly and spin down to have them back and usually it could work very well w/o problem.

klinmed

Posted 31 January 2012 - 12:12 PM

This is a well known problem in bio-banking. Usually it is best to use screw-caped tubes with rubber seals and store the tubes in small styrofoam boxes to minimize temperature shifts.
However, you are aliquoting very small volumes. Can you dilute say 20 fold in a buffer with a carrier protein and store 200 ul/tube as above? If you need to be carrier protein-free (for example for iodination) perhaps it would be better to freeze-dry the 10 ul aliquots.

klinmed

Posted 31 January 2012 - 12:13 PM

This is a well known problem in bio-banking. Usually it is best to use screw-caped tubes with rubber seals and store the tubes in small styrofoam boxes to minimize temperature shifts.
However, you are aliquoting very small volumes. Can you dilute say 20 fold in a buffer with a carrier protein and store 200 ul/tube as above? If you need to be carrier protein-free (for example for iodination) perhaps it would be better to freeze-dry the 10 ul aliquots.

zienpiggie

Posted 31 January 2012 - 12:17 PM

just curious, do you use a frost free freezer? I think the frost free freezer has a freeze thaw cycle to prevent frost from build up, but not great to prevent freeze thaw cycle from samples. That might be why your samples sublime?

microphobe

Posted 31 January 2012 - 03:00 PM

Thanks for your replies. No, frost-free freezers are a big no-no for our institute! I think you are right that the aliquots are too small, however I heard that diluting is also bad for antibody stability (does adding carrier protein overcome this? Like BSA or something?)

Has anyone tried overlaying with mineral oil, using siliconized tubes, smaller tubes, or adding glycerol? I have been toying with these ideas but obviously 18 months is a long time to wait and see what works!

Thanks.