Microcrystalline Cellulose (Avicel)
Inactive ingredient (gel binder, adsorption agent, flow improver)
Measuring cell: TGA850 with sample robot
Pan: Aluminum 100 µl, without a lid or with a pierced lid. The lid was pierced automatically immediately before the measurement (needle diameter 1 mm).
Sample preparation: As received, no preparation
TGA measurement: Heating from 30 °C to 300 °C at 20 K/min, all measurements are blank curve corrected.
Atmosphere: Nitrogen, 80 cm3/min
Cellulose and its derivatives easily take up water from the surroundings or release water depending on the humidity in the laboratory.
At the same heating rate, the release of moisture during the measurement occurs more rapidly if no lid is used than with a pierced lid. This has to be taken into account when comparing methods using open pans to methods in which pierced lids are used (sample changer operation). Samples which are in open pans on the sample changer turntable can lose moisture because of the relatively low humidity of the surroundings. The true moisture content of samples can be determined using sealed pans whose lids are pierced immediately before the measurement.
Onset temperature determination and integration of the melting peak of the DSC curve.
Pan | Step, % | Initial value of the curve sample weight *, % | Corrected step, % |
---|---|---|---|
Sealed, lid pierced immediately before the measurement | -4.8 | 99.9 | -4.9 |
Without lid | -4.1 | 99.1 | -5.0 |
*Original sample weight = 100%
The possible effect of the delay between the weighing out and the actual measurement of the sample must be investigated when determining the moisture content with TGA. When using pans with pierced lids, the smaller the hole in the lid the more the weight loss step is shifted to higher temperature.
Influence of the Pan on the Determination of Moisture Content, Cellulose | Thermal Analysis Application No. HB816 | Application published in METTLER TOLEDO TA Application Handbook Pharmaceuticals