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The relative efficiency of cryogens used for plunge‐cooling biological specimens
Author(s) -
Ryan K. P.,
Purse D. H.,
Robinson S. G.,
Wood J. W.
Publication year - 1987
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1987.tb01318.x
Subject(s) - thermocouple , propane , coolant , liquid nitrogen , freon , materials science , boiling , freezing point , pentane , boiling point , composite material , analytical chemistry (journal) , thermodynamics , chemistry , chromatography , physics , organic chemistry
SUMMARY Coolants 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.