The FMS Instrument
October 2011
Frequency Modulated Spectroscopy (FMS) is a non-destructive gas analysis technique for simultaneously monitoring moisture partial pressure and total headspace pressure in sealed parenteral containers.
Accurately estimating the moisture in a freeze dried product is necessary for a number of reasons including process monitoring, cycle control, regulatory purposes and validation. Underdried material (too high a moisture content) will often exhibit poor long term stability. However, overdrying may equally damage sensitive biologicals, for example live vaccines.
Traditional moisture analysis methods such as Karl Fischer titration (KF) and thermo-gravimetric analysis (TGA), tend to be slow and result in the destruction of the sample under test. Furthermore, KF titration and TGA do not distinguish between bound water, which is less chemically reactive, and active water, which has the greatest impact on product stability.
In FMS, light from a near-infrared laser is tuned to match an internal absorption frequency of the water molecule and passed through a container in the headspace above the product. The amount of laser light absorbed and the width of the absorption signal are used to calculate water vapour concentration and headspace pressure.
This process is non-destructive, allowing monitoring of production lines and long-term studies to be carried out on the same samples. FMS systems can be permanently situated in laboratories for product development, release testing and QC investigations, or alternatively can be mounted on carts and for in-process monitoring and troubleshooting.
FMS analysers from Lighthouse Instruments are now available in the UK and Ireland from freeze drying experts BPS.
BTL, our freeze drying consultancy arm, conducted research about FMS in conjunction with the manufacturers Lighthouse Instruments. (Links open in new window)
>>Applications of Headspace Moisture Analysis
>>A Study in Vial Headspace Moisture
>>Our freeze drying analytical instruments
Tags: FMS, frequency modulated spectroscopy, headspace moisture analysis, instruments, lighthouse instruments, moisture analysis, moisture determination