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Determining End Point During Laboratory Freeze Drying

Freeze drying, or lyophilizing, is an ideal method for evaporating or drying a heat sensitive sample, but it can be difficult to determine when the freeze drying process has reached complete dryness, or “end point.”

by Labconco
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Problem: Freeze drying in flasks, which is very common in laboratories, can be the most challenging sample type in which to determine end point. The current method requires visual inspection to determine if a sample is fully lyophilized, which often requires a lot of guess work.

If a sample has not reached end point and is removed from the lyophilizer prematurely, the ice will melt and rehydrate the sample cake that has been dried. For many applications, this would require the entire cake to be resuspended and the process to begin all over. Because of the need to start over and the inability to determine when the freeze drying is complete, many freeze dry runs are extended beyond their end point. The unnecessary extension of the freeze dry run wastes precious time.

Solution: Fortunately, modern sensor technology can detect the end-point condition for optimum efficiency. The End-Zone™ End Point Detection System by Labconco takes the guess work out of determining when end point is reached during flask freeze drying. Utilizing two vacuum sensors, it detects the end point by comparing the vacuum level of a sample flask to the vacuum level of an empty freeze dryer valve. Because the presence of vapor molecules within the flask raises the vacuum level, the vacuum level inside of a flask that is undergoing lyophilization will be higher than the system’s vacuum level. Once lyophilization has completed, vapor molecules are not present to elevate the vacuum level within the flask, thus the vacuum level in the flask becomes equal to the system vacuum level.

The EndZone Starter Kit requires a freeze dryer with the Lyo-works™ operating system. Lyo-works OS will display an alert when end point has been reached. If the FreeZone is connected to a network, the FreeZone can send an email to notify its user that freeze drying is complete.

The EndZone Starter Kit includes everything needed for end point detection of one flask. For use with more than one flask, the End-Zone Add On Kit is required.

For more information on the EndZone and FreeZone Freeze Dryers, visit