Some drugs are unstable at ambient temperature. So, to transport or store them, producers use, for example, dry ice. Nevertheless, a problem can occur : the carbon dioxide can be adsorbed on the drug and, when the product is heated back to ambient, this gas is desorbed and a overpressure appears. In order to simulate the conditions of transport and storage in dry ice, the sample is studied at -70°C under CO2 in a thermobalance. The mass variation brings out the adsorption.
The experiment is carried out with SENSYS TG-DSC.
The sample is a drug and is analyzed under CO2.
Mass = 19.7 mg
The following temperature program is used:
- Cooling from 25°C down to -70°C at 1K.min-1 under CO2.
- Waiting at -70°C during 30min under CO2.
- Heating from -70°C up to 25°C at 5K.min-1 under CO2.
Aluminium crucibles have been used.
During the cooling under CO2, the sample’s mass increases rapidly. The carbon dioxide is adsorbed on the drug. This adsorption goes on during the isotherm at -70°C and the global gain mass observed is 3.4%.
When the sample is heated back to ambient, its mass decreases very quickly. All carbon dioxide is desorbed.