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Assessment of the degradation of Aspirin by Differential Scanning Calorimetry (DSC)

Assessment of the degradation of Aspirin by Differential Scanning Calorimetry (DSC)

Syed, A.R. and Antonijevic, Milan D. ORCID: 0000-0002-5847-7886 (2009) Assessment of the degradation of Aspirin by Differential Scanning Calorimetry (DSC). The AAPS Journal, 11 (Suppl.). ISSN 1550-7416

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Purpose. To study thermal stability of Aspirin and define thermal events that are associated with the thermal degradation of aspirin.

Methods. Experiments were performed using a DSC 823e (Mettler Toledo, Swiss). Aspirin is prone to thermal degradation upon exposure to high temperatures. The melting point of aspirin is 140.1±0.4ºC (DSC). Aspirin has been examined by heating samples to 120ºC, 155ºC and 185ºC with subsequent cooling to -55ºC and a final heating to 155ºC. Although different heating and cooling ranges have been used, only results obtained at a rate of 10ºC/min will be presented. All runs where conducted in hermetically sealed pans.

Results. Upon heating the sample to 120ºC no significant thermal event can be detected. After cooling the sample and reheating a glass transition can be observed at ~-8ºC, followed by the melting of aspirin at ~139ºC. By heating the sample to 155ºC melting of aspirin has been detected at ~139ºC. On cooling and subsequent heating a glass transition occurs at ~-32ºC, together with a broad crystallisation (onset at ~38ºC and peak maximum at ~57ºC) followed by a broad melting with an onset at 94ºC and peak maximum at ~112ºC. Finally, by heating the sample to 185ºC melting at ~ 139ºC was observed, and upon cooling and reheating a glass transition was detected at ~-26ºC and no further events could be recorded.

Conclusions. This research demonstrates that the degradation steps of Aspirin depend on the thermal treatment. The main degradation products of different thermal treatments are currently unknown it is clear that acetic acid, which is one of the degradation products, acts as an antiplasticiser by lowering the glass transition temperature. In addition, due to the presence of the degradation products in liquid form (observed by hot stage microscopy), Aspirin is still present in the sample and recrystallises during the second heating step and melts at much lower temperatures.

Item Type: Article
Additional Information: 2009 AAPS Annual Meeting. 8-12 November 2009. Los Angeles, California.
Uncontrolled Keywords: aspirin, thermal transition
Subjects: Q Science > QD Chemistry
R Medicine > RS Pharmacy and materia medica
Faculty / School / Research Centre / Research Group: Faculty of Engineering & Science > School of Science (SCI)
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Last Modified: 10 Feb 2020 11:58

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