Cryogenic agents

CRYOGENIC AGENTS

  • The cost of storing material at ultra low temperatures increases as the storage temperature decreases.
  • In general, the lower the storage temperature the longer the sperm motility and fertilty can be maintained.
  • Several cryogenic agents have been used for freezing and preservation of bovine semen viz. solid carbon dioxide (-79⁰C), liquid air (-183⁰C) and liquid nitrogen (-196⁰C).

Temperature of different cryogenic agents

  • Solid carbon dioxide : -79oC
  • Liquid air : -183oC
  • Liquid nitrogen : -196oC.

  • Since 1964 liquid nitrigen has almost entirely replaced solid Co2 (dry ice) in the storage of frozen semen.
  • Liquid nitrogen is the 4th coldest substance known.
  • It has a boiling point of -196⁰C at atmospheric pressure. Being a liquid it comes into good contact with the surface of the straws.
  • Hence a constant storage temperature is maintained throughout the straw.
  • Liquid nitrogen is colorless, odourless and most inert substance and hence it can safely be handled in preserving biological materials.
  • It is non-toxic as such and does not produce toxic or irritating vapour.
  • Liquid nitrogen is manufactured from atmospheric air.

  • Source of liquid nitrogen - Atmospheric air.
  • Atmospheric air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon and 0.039% carbon dioxide.

  • Atmospheric air is the rich source of oxygen, liquid nitrogen and contains 78% nitrogen by volume.
  • In industrial manufacture of liquid oxygen, liquid nitrogen arises as by-product.

Liquid nitrogen is a by-product in liquid oxygen preparation plants.

  • It has been reported that greater deterioration in motility and metabolic activity of spermatozoa occurs at -79⁰C storage than -196⁰C.

TOP
Last modified: Wednesday, 6 June 2012, 2:57 PM