Bioequivalence and Bioavailability Forum

Dear Bani!

❝ Can you please tell me why the deep freezer temperature requirement is usually only -20 or -70 degree centigrade for sample storage in bioanalytical facility.

Easy. You may obtain –20 ℃ with a commercical household freezer (although you have to set up a system for documenting the temperature and an emergency system on your own). Lab deep freezers come in two specs: –40 ℃ and –70 ℃. The latter ones offer the possibility of a CO₂ backup. They are nasty energy consuming beasts (1 kW/h).
There’s a rule of thumb which temperature to start with: If your drug is an ester, you most likely have to go with –70 ℃ (because esterases are still active at –20 ℃). You have to check during method validation, which temperature ensures long-term stability.

❝ Why not we go beyond say -100 or below for sample storage.

Even for most biologicals –70 ℃ is enough. There are simply no freezers avail­able reliably going below –70 ℃. If your compound is not stable at -70 ℃, you will have to go to –196 ℃ (liquid nitrogen).

Dear HS,

Thanks.

Bani