Determination of Primary Drying End Point

SP Industries, Inc has issued a new technical note that compares and contrasts different techniques for primary drying end point determination.

Freeze drying is the process of drying a product in a frozen state under vacuum to increase product stability, minimise the effects of oxidation and degradation, and increase the shelf-life of the product. The process has found application for preserving products including biologicals, bacterial cultures, water-damaged documents, tissue preparations, food and therapeutic products such as vaccines, drugs, antibodies and proteins. A critical point in the freeze drying process is when the last drop of solvent has been removed from the sample - the primary drying end point.

There are two types of vacuum gauges/sensors that are routinely used in modern pilot scale and production freeze drying and lyophilisation equipment. The technical note describes how capacitance manometers and Pirani vacuum gauges work as well as detailing their operational advantages and disadvantages. By taking convergence data from a freeze dryer equipped with both capacitance manometer and Pirani gauge sensors the authors

demonstrate a reliable technique for accurately determining the primary drying end point.