Final answer:
Verification of liquid nitrogen levels for stored skin should occur at intervals specified in the SOPM. This is crucial for maintaining specimens at the required ultra-low temperatures offered by liquid nitrogen tanks. Option d is correct.
Step-by-step explanation:
If skin is stored in liquid nitrogen, documented verification of the liquid nitrogen level must occur at intervals specified in the SOPM. SOPM stands for Standard Operating Procedure Manual, a document that provides detailed, written instructions of protocols for maintaining and checking equipment and includes safety measures for handling such substances.
Since liquid nitrogen is a cryogenic substance used to maintain samples at ultra-low temperatures, it's essential to monitor and document its levels to ensure the specimens, such as skin grafts or medical specimens, are kept in optimal conditions to avoid deterioration. The interval for checks will vary according to institutional protocols and the specific needs of the stored material.
The importance of the proper storage of biological specimens cannot be overstated. For instance, cultures and other medical specimens, to remain viable, may need storage at temperatures below -70°C, which can be achieved through the use of liquid nitrogen. It's also worth comparing the cooling capabilities of liquid nitrogen to other methods; for example, the amount of cooling obtained from evaporating liquid nitrogen is significantly greater than from melting ice at 0°C due to its much lower boiling point.