mg
FREEZE-DRYING
the following characteristics : 1) Vials can be sealed under vacuum or after the introduction
of different gases into the chamber. 2) ApproXimately 1,200 vials containing 1-2 ml of a
suspension of virus can be dried simultaneously; 3) Because a liquid nitrogen condenser
is used, minimizing back—diffusion of water molecules, suspensions can be dried to a
residual moiSture content of less than 0.5 %; 4) Through the use of a 4—inch throat, oil
di‘usion pump, vacuums of 10*5 Torr or better in the chamber can be reached, this
increases the eîciency of drying markedly; 5) By using direct gas expansion, mechanical
refrigeration on the shelves and heaters bonded thereto, shelf temperature during
the drying cycle can be set from alow of — 60 °C to a high of + 50 °C; 6) By bucking
refrigeration against heating, the variations in shelf temperatures can be held to :}: 0.3 °C.
Thus, the conditions f0und to be best suitedto minimize inactivation of virus during drying
on the manifold apparatus can be duplicated under closely controlled conditions in the
chamber freeze—dryer. This apparatus would have direct application also for preparing
small lots of dried vacines for eld testing.
ACCELERATED TEST FOR PREDICTING' THE ' STABILITY OF LIQUID
OR DRIED SUSPENSIONS OF vuwsns
We have published recently an accelerated storage test for predicting the stability of
suspensions of viruses dried by sublimation in vacuo. This procedure has been extended
also to predicting the stability of liquid suspensions of viruses stored at + 4 °C. Briey,
the method is based on the observation thata "suitable metameter of the potency (the
potecy itself of its logatrithm) declineS, at a selected temperature, linearly with time;
further, "that_di‘erent rates of decline inpoteäncy obtained at different temperature are
related
these temperatures and follow the logarithmic form of the Arrhenius equation :
_—
log k-'=
R)‘ (1/T),
[l]
WhereT is absolute temperature, k is the reaction ratebf degradation of the suspension
of Virus; R is the gas c0nstant and AHa is dened as the heat of activation. Any value
proportional to thereatction “rate k would permit determination of the slope of the plot,
log k
1 /T,—'ad, therefore'calculation of the'heat of activation._lf the relationship above,
kat 'e1‘evated temperature vsÇ therecipr‘ocals of the absolute temperatures, is reasonably
linear, reaction rates during ”storage "at, low temperatures can be 'cal‘cülated from the experireaction r‘ates at=èlevated
rates, being much
‘aï…relatively}short time
’
»
_
_
,—Tqfæg+ theforegoing,the … titers of liquid; suspenSions of m‘easleS Virusbr suspensions
,
*
Virus dried by Sublimation
itiallÿ and at several
‘Carfrîed ;out "at three di‘erent
ï},
temperatures,soselected that,their
m1œs were_in_ arithmétical pro gresgi
smnTheequaüonusedfœ theabovewas
__
…
«
+. ;
T1+ 273_T0+273+Î9ÊÊ5
, : :
[2]
Where, To : loW=temperature, T1
intermediate temperatureaud ”Tg : hightemperature.
The low and high temperatures for b0th’Systems,
dried
based
on the data Of preliminary «experiments:
the
selected
FREEZE-DRYING
the following characteristics : 1) Vials can be sealed under vacuum or after the introduction
of different gases into the chamber. 2) ApproXimately 1,200 vials containing 1-2 ml of a
suspension of virus can be dried simultaneously; 3) Because a liquid nitrogen condenser
is used, minimizing back—diffusion of water molecules, suspensions can be dried to a
residual moiSture content of less than 0.5 %; 4) Through the use of a 4—inch throat, oil
di‘usion pump, vacuums of 10*5 Torr or better in the chamber can be reached, this
increases the eîciency of drying markedly; 5) By using direct gas expansion, mechanical
refrigeration on the shelves and heaters bonded thereto, shelf temperature during
the drying cycle can be set from alow of — 60 °C to a high of + 50 °C; 6) By bucking
refrigeration against heating, the variations in shelf temperatures can be held to :}: 0.3 °C.
Thus, the conditions f0und to be best suitedto minimize inactivation of virus during drying
on the manifold apparatus can be duplicated under closely controlled conditions in the
chamber freeze—dryer. This apparatus would have direct application also for preparing
small lots of dried vacines for eld testing.
ACCELERATED TEST FOR PREDICTING' THE ' STABILITY OF LIQUID
OR DRIED SUSPENSIONS OF vuwsns
We have published recently an accelerated storage test for predicting the stability of
suspensions of viruses dried by sublimation in vacuo. This procedure has been extended
also to predicting the stability of liquid suspensions of viruses stored at + 4 °C. Briey,
the method is based on the observation thata "suitable metameter of the potency (the
potecy itself of its logatrithm) declineS, at a selected temperature, linearly with time;
further, "that_di‘erent rates of decline inpoteäncy obtained at different temperature are
related
these temperatures and follow the logarithmic form of the Arrhenius equation :
_—
log k-'=
R)‘ (1/T),
[l]
WhereT is absolute temperature, k is the reaction ratebf degradation of the suspension
of Virus; R is the gas c0nstant and AHa is dened as the heat of activation. Any value
proportional to thereatction “rate k would permit determination of the slope of the plot,
log k
1 /T,—'ad, therefore'calculation of the'heat of activation._lf the relationship above,
kat 'e1‘evated temperature vsÇ therecipr‘ocals of the absolute temperatures, is reasonably
linear, reaction rates during ”storage "at, low temperatures can be 'cal‘cülated from the experireaction r‘ates at=èlevated
rates, being much
‘aï…relatively}short time
’
»
_
_
,—Tqfæg+ theforegoing,the … titers of liquid; suspenSions of m‘easleS Virusbr suspensions
,
*
Virus dried by Sublimation
itiallÿ and at several
‘Carfrîed ;out "at three di‘erent
ï},
temperatures,soselected that,their
m1œs were_in_ arithmétical pro gresgi
smnTheequaüonusedfœ theabovewas
__
…
«
+. ;
T1+ 273_T0+273+Î9ÊÊ5
, : :
[2]
Where, To : loW=temperature, T1
intermediate temperatureaud ”Tg : hightemperature.
The low and high temperatures for b0th’Systems,
dried
based
on the data Of preliminary «experiments:
the
selected