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An investigation into the low temperature thermal behaviour of Vitamin E Preparation USP using differential scanning calorimetry and low frequency dielectric analysis

Barker, S.A., Yuen, K.H., Craig, D.Q.M. (2000) An investigation into the low temperature thermal behaviour of Vitamin E Preparation USP using differential scanning calorimetry and low frequency dielectric analysis. Journal of Pharmacy and Pharmacology, 52 (8). pp. 941-947. ISSN 0022-3573. (doi:10.1211/0022357001774822) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:78872)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided. (Contact us about this Publication)
Official URL
https://doi.org/10.1211/0022357001774822

Abstract

The thermal and dielectric responses of Vitamin E Preparation USP have been examined to further understand the melting and solidification of this material. A TA Instruments 2920 Differential Scanning Calorimeter was used to examine the thermal response of the sample at a range of scanning speeds. Isothermal dielectric studies were performed using a Novocontrol Dielectric Spectrometer over a range of temperatures down to − 70°C and a frequency range of 106−10−2 Hz. The differential scanning calorimetry (DSC) studies showed an anomalous response whereby at slow heating rates (2°C min−1) a small exotherm followed immediately by an endotherm was observed. This response was considerably diminished in magnitude at higher rates (5°C min−1) and was not observed at the fastest heating rate of 10°C min−1. No thermal events were seen on cooling the sample to −60°C. It was suggested that the material formed a glass on cooling, with a predicted transition temperature of approximately −100°C. Further studies using a liquid nitrogen cooling system indicated that the system did indeed exhibit a glass transition, albeit at a higher temperature than predicted (ca −63°C). Low frequency dielectric analysis showed a clear relaxation peak in the loss component, from which the relaxation time could be calculated using the Havriliak‐Negami model. The relationship between the relaxation time and the temperature was studied and was found to follow the Vogel‐Tammann‐Fulcher (VTF) modification of the Arrhenius equation. It is therefore concluded that Vitamin E Preparation USP is a glass‐forming material that exhibits kinetically‐hindered recrystallisation and melting behaviour. The study has also indicated that DSC and low frequency dielectric analysis may be powerful complementary tools in the study of the low temperature behaviour of pharmaceuticals.

Item Type: Article
DOI/Identification number: 10.1211/0022357001774822
Uncontrolled keywords: alpha tocopherol, article, crystallization, differential scanning calorimetry, electrochemical analysis, low temperature procedures, melting point, physical chemistry, thermodynamics
Divisions: Faculties > Sciences > Medway School of Pharmacy
Depositing User: Susan Barker
Date Deposited: 27 Nov 2019 13:45 UTC
Last Modified: 27 Nov 2019 13:45 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/78872 (The current URI for this page, for reference purposes)
Barker, S.A.: https://orcid.org/0000-0003-4880-0253
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