The relative efficiency of cryogens used for plunge‐cooling biological specimens
作者:
K. P. Ryan,
D. H. Purse,
S. G. Robinson,
J. W. Wood,
期刊:
Journal of Microscopy
(WILEY Available online 1987)
卷期:
Volume 145,
issue 1
页码: 89-96
ISSN:0022-2720
年代: 1987
DOI:10.1111/j.1365-2818.1987.tb01318.x
出版商: Blackwell Publishing Ltd
关键词: Cryogens;plunge‐cooling;coolants;ethane;propane;thermocouples;cooling rates;hydrated gelatin specimens;epoxy resin specimens;latent heat;vapour formation
数据来源: WILEY
摘要:
SUMMARYCoolants used for freezing biological specimens were tested for cooling performance in the continuous plunge mode. Results from bare thermocouples showed that ethane cooled faster than propane or a propane: pentane mixture, even when warmed to 25 K above its freezing point. Propane coolants were more efficient than Freon 22 and the slowest cooling occurred in boiling liquid nitrogen. Hydrated gelatin specimens showed similar results with ethane cooling about 33% faster than propane. Epoxy resin specimens cooled faster than hydrated gelatin specimens of similar size. Hydrated and resin specimens cooled over increasing distances as plunge velocity increased. A bare thermocouple, however, cooled over a constant distance when plunged above a critical velocity. This phenomenon may reflect vapour formation and its suppression at high plunge velocities. The rate of cooling in hydrated specimens is shown to have an absolute limit and cannot be modelled by bare thermocouples or resin specimens.
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