The Development of Gas-flow Modulation for High-frequency MTDSC measurements |
| |
Authors: | P G Royall D Q M Craig M Reading T J Lever |
| |
Institution: | (1) The School of Pharmacy, The Queen's University of Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Northern Ireland, United Kingdom;(2) ITPME, Loughborough University, Loughborough, Leicester, LE11 3TU, United Kingdom;(3) TA Instruments Ltd., Leatherhead, KT22 7UQ, United Kingdom |
| |
Abstract: | The purpose of this study was to investigate the feasibility of modulating the temperature programme of a conventional DSC
by use of an alternating gas-flow system. Modulated temperature differential scanning calorimetry (MTDSC) is an important
thermal analysis technique but suffers from a limited applicable frequency range due to the mass of the sample and DSC cell
leading to the impingement of thermal conductivity effects. We suggest that the frequency limit can be increased by replacing
the cell as the source of temperature modulation with an external gaseous source, directed towards the sample and reference
pans. In this evaluation, an alternating gas-flow was passed through a line to a forced gas-flow accessory (FGFA). The FGFA
consisted of two matched cylinders containing chambers that allowed pre-temperature-equilibration of the stream of gas before
it was passed over the sample and reference pans. The development of this device revealed the essential practical requirements
of gas-flow modulation for high-frequency temperature modulation. These include the following: an appropriately sealed tunable
gas supply to both sample and reference pans, an effective method for high-frequency cycling of the gas-flow rate, a small
aperture to deliver the flowing gas directly over the pan and a temperature equilibration chamber. The results from samples
of quenched PET and amorphous Saquinavir indicate that gas-flow modulation is indeed feasible, with the FGFA able to raise
the attainable temperature modulation frequency by an order of magnitude compared to conventional MTDSC.
This revised version was published online in August 2006 with corrections to the Cover Date. |
| |
Keywords: | forced gas-flow accessory gas-flow modulation high-frequency temperature modulation MTDSC PET and Saquinavir |
本文献已被 SpringerLink 等数据库收录! |
|