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NEWSLETTER OF eurostar-science |
NO 5 -- February 27, 2003 |
CONTENT
5.1 Editorial5.1 EDITORIAL |
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PhandTA 7 - the
7th International Conference on Pharmacy and Applied
Physical Chemistry - will be held from Sunday, September 7 to
Thursday, September 11, 2003 at the University of Innsbruck. The
location of our Conference is the so-called SOWI - Sozial- und
Wirtschaftswissenschaftliche Fakultät - a very modern and ideally
located building. Even more important is the structure of this
building in all respects, extremely practical for our activities such
as the communications, the poster presentations, the workshops, the
exhibition of instruments and also for meetings and discussions during
lunch time. The start of the Conference is planned for Sunday afternoon, approximately at 4 pm with 3 to 4 major communications. The Scientific Program is anticipated in our usual way in presenting of quite large subjects within our Conference Sections and with extensive discussions. The percentage of scientifically active participants in our preceding conferences was rather high which is the base for a Conference on an outstanding level. You will find all necessary information in the Circular we distributed already, in this Newsletter and in detail on our Conference website. I would like to invite you all in the name of the Members of the Organization Committee to participate at the PhandTA 7 in Innsbruck. The Pharmaceutical Institutes of Innsbruck represent an rather old tradition and are with Professor Ulrich Griesser among others Scientists on the way to make the important scientific steps in the direction of the demands in our rather young century. Erwin Marti, President |
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5.2 News |
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![]() As already announced and mentioned above, the preparation of PhandTA 7, the 7th International Conference on Pharmacy and Applied Physical Chemistry, has started. The venue will last 3 and a half days followed as during PhandTA 6 by a one-day workshop whereby its subject will be announced later. All necessary information on this event will ongoingly be completed and is available at the conference website:
The organization on an accomodation is on your own responsibility. A list of recommendable hotels will be available by end of March. Registration is possible either online on the website or by fax/mail. Payment of the registration fee is appreciated beforehand the conference. To be ongoingly
informed on all relevant news and changes, you may register at the
website for our electronical Conference Newsticker. |
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![]() Mettler-Toledo GmbH
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5.3 Our Sponsors. Mettler-Toledo GmbH | ||||
Investigation of spray-dried substances.
Drying and glass transition using IsoStep Dr. Jürgen Schawe, Dr. Uwe Hess Mettler-Toledo GmbH, Analytical,CH-8603 Schwerzenbach | ||||
Introduction
If several thermal events occur simultaneously in a DSC measurement, the problem is then how to separate
the different processes involved. Often, a change in heat capacity is overlapped by exothermic or endothermic peaks,
e.g. through chemical reactions, crystallization or vaporization. One possible way to separate the different processes is
to vary the measurement conditions in the conventional DSC. For example, heating and cooling measurements can be
performed at different rates and in different temperature ranges using different types of crucible. This is of course relatively
time-consuming. | ||||
Experimental details
The DSC measurements were performed with a DSC822e equipped with an IntraCooler. The STARe
software with the IsoStepTM option was used for the evaluation. | ||||
Results
and
interpretation
Figure
1
shows
a
typical
IsoStepTM
measurement
curve
as
a
function
of
the
temperature.
The
upper
limit
of
the
curve
corresponds
to
the
heat
flow
during
the
isothermal
segments,
from
which,
the
non-reversing
curve
is
calculated. | ||||
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Figure
1.
IsoStepTM measurement as a function of the temperature of a sample that had been preheated at 80 °C for 20 min | |||
Figure
2
shows
the
heat
capacity
and
the
non-reversing
curves
of
the
material
that
had
been
heated
beforehand
for
20 minutes.
In
the
heat
capacity
curve,
two
glass
transitions
can
be
seen
at
about
70°C
and
125°C.
The
broad
vaporization
peak
observed
in
the
non-reversing
curve
overlaps
both
glass
transitions.
This
peak
is
so
large
that
the
glass
transitions
are
not
resolved
in
a
conventional
DSC
curve.
The
first
glass
transition
depends
on
the
water
content
and
is
responsible
for
the
powder
sticking.
Its
glass
transition
temperature,
Tg,
was
therefore
investigated
as
a
function
of
water
content.
In
the
heat
capacity
curves
(Fig.
3),
one
can
see
the
shift
of
the
glass
transition
temperature
to
higher
temperature
after
longer
drying
times. | ||||
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Figure
2.
Specific heat capacity and non-reversing curves as a function of the temperature or measurement time, calculated from the measurement in Figure 1. The hatched area shows the amount of water vaporized up to the glass transition temperature. | |||
The
water
content
before
the
measurement,
wini,
is
of
course
not
the
same
as
the
water
content
at
the
glass
transition
temperature,
wTg,
because
water
escapes
continuously
from
the
sample
during
the
measurement.
This
loss
of
water
can
be
determined
from
the
non-reversing
curve
by
evaluating
the
partial
peak
area
up
to
Tg.
The
relevant
partial
peak
area,
D
hp,
is
shown
by
the
hatched
area
in
Figure
2.
If
the
specific
heat
of
vaporization
of
water,
D
hw,
is
known,
the
water
content
up
to
Tg
can
be
determined
from
the
equation ![]() D hw can be determined from the total peak area on vaporization, D H, and the loss of mass during the measurement, D m, (determined by re-weighing): D hw = D H/Dm [4]. A value of 2500 J/g was obtained for D hw[1]. This is somewhat greater than the value for free water (2400 J/g). | ||||
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Figure 3.
Heat capacity curves measured after different drying times at 80°C. The parameter is the drying time. The arrows point to the glass transition temperatures. | |||
The glass transition temperatures determined from the curves in Figure 3 are
displayed in Figure 4 as a function of the water content, wTg Eq.(1)). This diagram can be used to optimize the
processing conditions for the material. | ||||
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Figure 4.
Glass transition temperature as a function of water content at Tg. | |||
SUMMARY
With IsoStepTM,
the heat capacity and the non-reversing curve can be determined
simultaneously in one measurement. This allows glass transition and
vaporization processes to be separated. With a spray-dried
pharmaceutical substance, it has been shown that the method can be
used to quantitatively determine the effect of moisture on the glass
transition temperature. The measurement procedure features easy sample
preparation, direct measurement and high accuracy. | ||||
LITERATURE [1] M. Schubnell, J.E.K. Schawe, Int. J. Pharm., 192
(2001) p.173 | ||||
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