Freeze Drying Processes

The main freeze drying processes are:

  • Drying in round-bottom flasks, wide-neck filter bottles, ampoules, etc. (‘outside’ method). The product is pre-frozen externally in a freezer or a cooling bath and then connected to the freeze dryer through a three-way rubber valve. Each vessel can be attached and removed individually.
  • Drying products in dishes, vials or similar containers on shelves (in some cases heatable) outside the ice condenser chamber (‘outside’ method). The product is pre-frozen externally in a freezer or a chilling bath and then dried under an acrylic or stainless steel cover. Removing individual specimens during the process is not recommended (risk of thawing).
  • Freezing and drying in dishes, vials or similar containers inside the ice condenser chamber (‘inside’ method). In this case the entire process can be carried out inside the unit without additional product handling and be fully automated if necessary. Freezing results from chilled air (convection), possibly accelerated by forced air circulation with a fan. Particularly recommended for expensive and/or sensitive products (low freezing point < 25 °C)
  • Freezing and drying in dishes, vials or similar containers on cooled and heated shelves. Here as well the entire process can be carried out fully automatically inside the drying chamber without additional product handling. Freezing results from direct contact with the cold shelf (conduction). Standard method at production scale and in pilot systems for process development or optimisation.

The two options for drying with Christ laboratory units from Alpha to Delta:

Inside method / Single-chamber

With this configuration the product is frozen inside the ice condenser chamber and then dried. This method is particularly suitable for substances with low freezing points or thermally unstable substances. In this method, the shelves are located directly in the ice condenser chamber. Freezing can also be assisted by a fan. A stoppering device for vials may optionally be used.

Outside method / Double-chamber

With this configuration the product is separately pre-frozen and then dried above the ice condenser chamber. This method allows a large variety of accessories to
be used. An intermediate valve can be used to separate the product chamber from the ice condenser chamber for the pressure increase test to determine the drying endpoint.

Process monitoring / Optimisation tools / Process Analytical Technologies (PAT)

  • Comprehensive process monitoring is necessary in the development and subsequent production of high-value products, particularly in the biotech and pharmaceutical sectors, for internal quality assurance and regulatory compliance documentation.
  • Process analytical technologies, which include everything from product temperature sensors to online mass spectrometers, provide insight into complex processes and enable stable drying processes.

As a technology leader, we provide the following tools for our customers

  • WTMplus – wireless online product temperature measurement
  • LyoBalance – online measurement of drying progress by precision weighing
  • LyoControl – eutectic point determination and process control
  • Manometric product temperature measurement
  • Pressure increase test for drying endpoint determination
  • Comparative pressure measurement for endpoint determination

    We would be pleased to conduct trials with your products in our
    application lab. We look forward to your challenges!

The main processes in Vacuum Concentration (RVC) are

  • Drying samples (often very small) for subsequent analysis, such as DNA analysis or forensic analysis. e.g. Eppendorf caps or MTP/deepwell plates, test tubes up to approx. 20 ml, organic or aqueous solvents
  • Concentrating or drying large-volume samples in laboratory analytics and pharmaceutical research in vials or round-bottom flasks up to 500 ml, with organic or aqueous solvents
  • Evaporation of aggressive acids, e.g. hydrochloric acid (HCl) for sample preparation