lyophilization

Question 1

introduction

Answer 1

-the process of isolation of a solid substance from the solution by freezing the solution and vaporizing the ice way under vacuum conditions
-it is the sublimation from frozen substances
-it involves triple point of substance

Question 2

triple point

Answer 2

it is the point having the definite temperature and pressure at which the soids, liquids and vapor phases of a chemical entity are able to co exist

Question 3

steps

Answer 3

-pre-treatment

Question 4

pre-treament

Answer 4

freezing of solids:
before aplying the vacuum the liquid is firstly frozen, this process is called pre-freezing and is done by following ways:
-shell freezing
-vertical freezing

drying:
after pre-freezing the substance is dried there are two types of drying:
-primary drying
-secondary drying

Question 5

shell freezing

Answer 5

in this methods the liquid is taken in a bottle and is rotated slowly, horizontally in a refrigerator bath. so that material freesez as a thin shell along the walls of bottle. in this way not only the surface area for sublimation is increases but also heat transfer is increases

Question 6

vertical freezing

Answer 6

in this method the bottles are first chilled and then rotated individually in vertical position in the presence of steam of very colid air. so, by this process small crystals of ice are formed. moreover this process is very rapid

Question 7

primary drying

Answer 7

it means to supply the latent heat of vaporization. the apparatus used for this process is “vacuum oven” or container attached to invidual outlet. the latent heat of sublimination of substance is provided and so vapors formed are removed. By this process 99.5% moisture is removed

Question 8

secondary drying

Answer 8

after primary drying the substance is subjected to vacuum drying to remaining 0.5% moisture. And this is called as secondary drying. temperature during this drying is raised to 60-60C

Question 9

annealing

Answer 9

Increasing temperature but below melting and then holding to allow crystal growth is called as annealing. Some amorphous products (such as mannitol or glycine) form a metastable glass with incomplete crystallization when first frozen. These products can benefit from a thermal treatment process, which is also called annealing. During annealing, the product temperature is cycled (for example: from -40C to -20C for a few hours and then back to -40C) to obtain more complete crystallization. Annealing has the added advantage of larger crystal growth and corresponding shorter drying times.

Question 10

packaging

Answer 10

the packaging of freeze dried product is very important b/c the freeze dried products must be protected from moisture. for this purpose the poduct is packed is vacuum container or the closing is carried out under controlled conditions of atmospheric to avoid contact with moisture

Question 11

properties of FD material

Answer 11

-amosphous and highly porous
-takes moisture immeadiately and tends to crystallize
-enormous surface area

Question 12

advantages of freeze-dried products

Answer 12

-product is dried without any elevated temperature
-this process is also good for oxygen and sensitive drugs
-the product is in porous form, thats why it can be reconstituted rapidaly
-constitutes of the dried material remained homogenouslt dispersed
-streility of the product can be achieved and maintained
-due to low temperatures enzyme activity and decomposition (hydrolysis) is stopped

Question 13

disadvantages if FD products

Answer 13

-volatile compounds may be removed
-single operation is very expensive
-the process is slow
-stability problem associated with individual drugs

Question 14

desired characteristics of freeze-dried product

Answer 14

-sufficient strength
-uniform colour
-suffecient dryness
-suffeciant porosity
-sterility
-free of pyrogens
-free of particulates
-chemical stability

Question 15

applications

Answer 15

-drug prevention method as
lowers water activity
reduces potential for microbial growth
-dry the heat sensitive products
biotechnology products
biological drugs (proteins, seras)
-long shelf life of drugs
-enzymes (hylauranidase) and hormones (insulin) are also dried by this process
-amosphous and possesses enormous surface area
-this process is used for the drying of proteins and peptides
-this process is used in recombinant DNA technology. hence, used for the manufacturing of various pharmaceuticals and biological product which are thermolyophils

Question 16

difference between sublimation and lyphilization

Answer 16

in sublimation the K.E. of the the molecule is very high and so molecules are directly converted into vapours. in lyophiization is carried out in controlled temperature and pressue. The K.E of the molecule is not sufficient to concert it in to vapors, so in this proess the substance is first converted into liquid and then to vapour