TY - JOUR
T1 - The role of space charge formation in the generation of thermally stimulated current (TSC) spectroscopy data for a model amorphous drug system
AU - Antonijevic, Milan D.
AU - Craig, Duncan Q. M.
AU - Barker, Susan A.
PY - 2007/11/9
Y1 - 2007/11/9
N2 - Thermally stimulated current (TSC) spectroscopy is attracting increasing attention as a means of materials characterization, particularly in terms of measuring slow relaxation processes in solid samples. However, wider use of the technique within the pharmaceutical field has been inhibited by difficulties associated with the interpretation of TSC data, particularly in terms of deconvoluting dipolar relaxation processes from charge distribution phenomena. Here, we present evidence that space charge and electrode contact effects may play a significant role in the generation of peaks that have thus far proved difficult to interpret. We also introduce the use of a stabilization temperature in order to control the space charge magnitude. We have studied amorphous indometacin as a model drug compound and have varied the measurement parameters (stabilization and polarization temperatures), interpreting the changes in spectral composition in terms of charge redistribution processes. More specifically, we suggested that charge drift and diffusion processes, charge injection from the electrodes and high activation energy charge redistribution processes may all contribute to the appearance of shoulders and ‘spurious’ peaks. We present recommendations for eliminating or reducing these effects that may allow more confident interpretation of TSC data.
AB - Thermally stimulated current (TSC) spectroscopy is attracting increasing attention as a means of materials characterization, particularly in terms of measuring slow relaxation processes in solid samples. However, wider use of the technique within the pharmaceutical field has been inhibited by difficulties associated with the interpretation of TSC data, particularly in terms of deconvoluting dipolar relaxation processes from charge distribution phenomena. Here, we present evidence that space charge and electrode contact effects may play a significant role in the generation of peaks that have thus far proved difficult to interpret. We also introduce the use of a stabilization temperature in order to control the space charge magnitude. We have studied amorphous indometacin as a model drug compound and have varied the measurement parameters (stabilization and polarization temperatures), interpreting the changes in spectral composition in terms of charge redistribution processes. More specifically, we suggested that charge drift and diffusion processes, charge injection from the electrodes and high activation energy charge redistribution processes may all contribute to the appearance of shoulders and ‘spurious’ peaks. We present recommendations for eliminating or reducing these effects that may allow more confident interpretation of TSC data.
U2 - 10.1016/j.ijpharm.2007.11.004
DO - 10.1016/j.ijpharm.2007.11.004
M3 - Article
VL - 353
SP - 8
EP - 14
JO - International Journal of Pharmaceutics
JF - International Journal of Pharmaceutics
SN - 0378-5173
IS - 1-2
ER -