_
,
_
…
Thermal Analysis ,
'
,
,
m Freezmg and Freeze—Drng
,
—
.
‘
'
‘J.D.DAVIES
"
'
‘
*
,
_
DEPÀÈTŒAÈNT OF PAmômeŸ, UNi… on Cmmsz,
When liquid is present during the drying process there is always the
that either salt
concentration will damage the labile compound br that the—ihOl€cules, as they themselves
concentrate, will irreversibly aggregate. Such risks as these are merely reduced in methods
which depend upon a time—temperature phenomenon, i.e. drying at high temperatures
for a very short time. Theoretically, freeze—drying has a distinct advantage over such methods,
for although freezing croates a similar dehydration and concentratio, the reduced reactiOn
rates at low temperatures minimise the risk of such denaturation. Prévided that the sample
is cooled suicienv so that it is all in the‘solid state, moleCules are then iinnîobilised so
preventing their concentration and aggregation during the removal of water. The voids
left after the removal of the ice crystals confer the added advantage 1n that one is left with
a solid matrix of high solubihty.
Ï
.
In spite of these theoretical advantages early freeze-drying procedures often resulted
in the loss of the essential properties
compounds…»Sucœssful freeze-drÿing
techniques were in fact a matter
of trial and‘error. The condition Of
froZen
block emitting bubbles when submitted to Vacuum was
“ï‘referred to by FloSd0rf (1949)
and was christened “puing”. Greaves (1954) reéalledathat
a”quuid phase *
_
in early crude penicillin, frozen
20°C,
inverting‘ '’
the bottle, whence an oily liquid slowly separated from the froZen sothhese two points,
the frothing of the ice block under
separation of hqu1dfïom “the “ice block,
were suggested to act as guides in ndingthe highest
whiCh drying
could be carried out As stated earlier, from theoretical 'Consideratio11s drÿing should take
place from the
‘ïState;
the lowest
eûtectic temperature
the sample;
_
The
temperature of a substancemaybeexplamedbney in the follOwing
Oncooling a
e. g. a
a temperature, dependent
'
.
-
upon the salt
its 99n°eü%üoäa
mached when—ice Will—fsçpame from the
sOlùtiOn; As the temperature
,
_
…
Thermal Analysis ,
'
,
,
m Freezmg and Freeze—Drng
,
—
.
‘
'
‘J.D.DAVIES
"
'
‘
*
,
_
DEPÀÈTŒAÈNT OF PAmômeŸ, UNi… on Cmmsz,
When liquid is present during the drying process there is always the
that either salt
concentration will damage the labile compound br that the—ihOl€cules, as they themselves
concentrate, will irreversibly aggregate. Such risks as these are merely reduced in methods
which depend upon a time—temperature phenomenon, i.e. drying at high temperatures
for a very short time. Theoretically, freeze—drying has a distinct advantage over such methods,
for although freezing croates a similar dehydration and concentratio, the reduced reactiOn
rates at low temperatures minimise the risk of such denaturation. Prévided that the sample
is cooled suicienv so that it is all in the‘solid state, moleCules are then iinnîobilised so
preventing their concentration and aggregation during the removal of water. The voids
left after the removal of the ice crystals confer the added advantage 1n that one is left with
a solid matrix of high solubihty.
Ï
.
In spite of these theoretical advantages early freeze-drying procedures often resulted
in the loss of the essential properties
compounds…»Sucœssful freeze-drÿing
techniques were in fact a matter
of trial and‘error. The condition Of
froZen
block emitting bubbles when submitted to Vacuum was
“ï‘referred to by FloSd0rf (1949)
and was christened “puing”. Greaves (1954) reéalledathat
a”quuid phase *
_
in early crude penicillin, frozen
20°C,
inverting‘ '’
the bottle, whence an oily liquid slowly separated from the froZen sothhese two points,
the frothing of the ice block under
separation of hqu1dfïom “the “ice block,
were suggested to act as guides in ndingthe highest
whiCh drying
could be carried out As stated earlier, from theoretical 'Consideratio11s drÿing should take
place from the
‘ïState;
the lowest
eûtectic temperature
the sample;
_
The
temperature of a substancemaybeexplamedbney in the follOwing
Oncooling a
e. g. a
a temperature, dependent
'
.
-
upon the salt
its 99n°eü%üoäa
mached when—ice Will—fsçpame from the
sOlùtiOn; As the temperature