Biomedical Engineering Reference
In-Depth Information
4.2.2 Experimental
iGC was conducted using a surface energy analyser (SEA). Samples
were placed in 4 mm (internal diameter) columns, to give a total
surface area of approximately 0.5 m
2
. The following eluent vapours
were passed through the column: nonane, octane, hexane and
heptane. All reagents were of analytical grade. The injection of
vapours was controlled to pass a set volume of eluent through the
column to give pre-determined fractional coverage of the sample in
the column. The retention time of the vapours by the particles gives
an indication of the surface properties of the material, including the
surface energy. By gradually increasing the amount of vapour injected,
it is possible to build up a surface heterogeneity plot.
Specific surface area measurements were made using a Micromeritics
TriStar 3000 surface area and porosity analyser using the nitrogen
Brunauer-Emmett-Teller (BET) technique.
Thermogravimetric analysis (TGA) and differential thermal analysis
(DTA) experiments were performed in a simultaneous DTA-TGA
apparatus (Shimadzu DTG 60). Throughout the experiment, the
sample temperature and weight-heat flow changes were continuously
monitored. The conditions of measurement were: heat flow 10 °C/
min and dynamic atmosphere of nitrogen (50 ml/min). The range of
temperature measurement was from 40 to 500 °C.
Scanning electron microscopy (SEM) images were captured on a
Hitachi 6600 FEG microscope operating in the secondary electron
mode and using an accelerating voltage of 1 kV.
Powder rheology measurements were performed on a FT4 powder
rheometer. All experiments were performed at laboratory ambient
temperature (24 °C) and at a relative humidity of 43%.
The sample used was hyaluronate (sodium salt, of microbial
origin) in the form of a white powder and with a MW of 0.7 to 0.9
MDa. It was kept in dry conditions in a desiccator (at the ambient
temperature of 24 °C) for 4 weeks prior to the SEA and powder
rheology experiments.
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