Tolbutamide
Active ingredient (oral antidiabetic)
Measuring cell: DSC820
Pan: Aluminum 40 µl, hermetically sealed
Sample preparation: As received, no preparation
DSC measurement: for A, B, C: Heating from 30 °C to 100 °C. Cooling from 100 °C to 30 °C. Second heating run from 30 °C to 175 °C. The sample weight was 5.057 mg.
DSC measurement: for D, E: Heating from 30 °C to 175 °C. Cooling from 175 °C to 30 °C. Second heating run from 30 °C to 175 °C. The sample weight was 4.389 mg.
The heating rate for all the steps was 10 K/min, the cooling rate was 5 K/min.
Atmosphere: Nitrogen, 50 cm3/min
Different peaks can be observed, depending on the maximum temperature reached. The first peak at about 40 °C is, however, only reversible if the sample is not heated above 100 °C. It is caused by an enantiotropic solid-solid transition. If the melting temperature is first exceeded (>140 °C) and the sample afterwards cooled down, then a new modification can be observed with a broad melting range in the second heating run. The broad peak shape indicates the presence of impurities arising from decomposition.
First peak | Middle peak | Melting peak | ||||
---|---|---|---|---|---|---|
Onset, °C | ΔH, J/g | Onset, °C | ΔH, J/g | Onset, °C | ΔH, J/g | |
A Heating run 1 | 39.5 | 7.7 | - | - | - | - |
B Heating run 2 | 36.2 | 6.2 | - | - | - | - |
C Heating run 3 | 39.5 | 7.5 | - | - | 126.4 | 90.9 |
First peak | Middle peak | Melting peak | ||||
---|---|---|---|---|---|---|
Onset, °C | ΔH, J/g | Onset, °C | ΔH, J/g | Onset, °C | ΔH, J/g | |
D Heating run 1 | 39.3 | 7.1 | - | - | 126.9 | 91.5 |
E Heating run 2 | - | - | 91.4 | 44.8 | - | - |
Different modifications of the sample are formed depending on the thermal pretreatment. The modifications can be clearly distinguished with DSC.
Polymorphism, Tolbutamide | Thermal Analysis Application No. HB832 | Application published in METTLER TOLEDO TA Application Handbook Pharmaceuticals