Pseudopolymorphism, Glucose Monohydrate - METTLER TOLEDO

Pseudopolymorphism, Glucose Monohydrate

SampleGlucose

Glucose, monohydrate and the anhydrous form

 

Application

Glucose, monohydrate

 

Conditions

Measuring cellsDSC820 or TGA850

Pan: Aluminum 40 µl or 100 µl, both with pierced lids

Sample preparation: As received, no preparation

DSC measurement: Heating from 30 °C to 250 °C at 20 K/min

TGA measurement: Heating from 30 °C to 300 °C at 20 K/min

Atmosphere: Nitrogen, DSC: 50 cm3/min, TGA: 80 cm3/min

 

 

 

Interpretation

Glucose can exist as the monohydrate or in the anhydrous form. The TGA curves show that the two forms differ quite distinctly from one another. The anhydrous form shows no loss of moisture, whereas with the monohydrate the elimination of water can be observed. This results in a step of about 7% and is slightly below the value of 9.1% expected stoichiometrically.

 

Evaluation TGA

The weight loss is determined.

SampleStep, %Evaluation range, °C
Monohydrate7.142-145
Anhydrous form<0.142-145

 

 

 

Interpretation

The anhydrous form exhibits only the melting process at about 161 °C. The monohydrate shows a very broad peak resulting from the elimination of water and the transformation to the anhydrous form. This then melts at about 158 °C. The smaller heat of fusion and lower melting point in comparison with the anhydrous form, indicate an incomplete crystallization.

 

Evaluation DSC

The onset temperatures and peak areas are determined.

SampleFirst peakSecond peak
Onset, °CΔH, J/gOnset, °CΔH, J/g
Monohydrate71.452.6153.9162.4
Anhydrous form--160.9198.7

 

Conclusion

The DSC and the TGA curves allow the identification of the monohydrate and anhydrous forms.

 

Pseudopolymorphism, Glucose Monohydrate | Thermal Analysis Application No. HB834 | Application published in METTLER TOLEDO TA Application Handbook Pharmaceuticals