Application Note
Freeze-Dried Cakes — Where Is The Water?
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•Application Note: Freeze-Dried Cakes — Where Is The Water?
By Isobel Cook and Kevin Ward, Biopharma Technology Ltd.; and Derek Duncan, Lighthouse Instruments LLC
Water may be present in a variety of "forms" – free, adsorbed, chemically bound, hydration shells (e.g. of proteins), water of crystallisation, not all of which may be directly linked to the activity or stability of the product in question. Currently the best established water detection methods, Karl Fischer (KF) titration and thermo-gravimetric analysis (TGA) do not necessarily allow the operator to distinguish between one form of water and another.
In this study, a number of freeze dried cakes have been analysed, ranging from purely amorphous to completely crystalline, using KF and FMS (frequency modulation spectroscopy). KF titration is a well established and FDA recognised technique for moisture analysis and is generally considered to measure the total water within the vial containing the freeze dried cake, if the sample is wholly soluble in KF medium. FMS analysis is a relatively new technique that measures the moisture and pressure in the vial headspace and is a non-destructive technique, allowing the same sample to be monitored over time. The aim of the present study is to understand the relationship between the moisture measured by KF/FMS and further our understanding of productwater interactions within a freeze dried cake.
Click Here To Download:•Application Note: Freeze-Dried Cakes — Where Is The Water?
