Filter Integrity

• Filter integrity testing is an essential procedure to detect defective Sterilize filter cartridges.
• The filter Integrity test one of the most important test that are carried out on the final product. 
• A satisfactory result from this test gives assurance that the final product is sterile and therefore acceptable for human use.
• The membrane filter integrity test is not mentioned in the International Pharmacopoeia.
• However, it is a requirement of GMP guidelines on aseptic processing using final sterilizing filtration.
• It is highly recommended that the test is performed prior to release of the product.
• Different types of filter integrity machines available in market.

1. Pall Corporation Ltd
2. Merk-Millipore
3. Sartorious 

Different size of filters Integrity ;

a) 20 inch Sterilize filters  

b) 10 inch Sterilize filters

c) 5 inch Sterilize filters

d) 4 inch Sterilize filters (Vent filters or Cartridge filters)

e) 0.45μm Sterilize filters

f) 0.22μm Sterilize filters

Types of test 

1. Bobble point test (BPT)

2. Diffusion Test (DIFT)

3. Combined Test (BPT + DIFT)

4. Pressure Drop Test / System Leak Test

5. Water Flow Test (WFT)

Filter 2 types :

a) Hydrophobic Filter :

• will not pass in water but will wet in low surface tension liquids.
• Example organic solvents or alcohols.
• 0.45μm Sterilize filters
• This filters are best suited for gas filtration, low surface tension liquids and venting.
• wetting purpose used 60% Iso Propyl alcohol.

b) Hydrophilic Filters:

• Easily wet with water.
• This filters are best suited for aqueous solutions.
• filter integrity used cooled WFI (20°-25°C)

Filter wetting :

• Wet the filter with the appropriate fluid,typically water for hydrophilic membranes or an alcohol / water mixture for hydrophobic membranes.

1 millibar (mbar) = 0.01450 PSI (pounds per square inch)

1PSI = 68.9475 millibar

15 PSI= 68.9475 X 15 =1034.2131 millibar

1380 millibar = 20.01 PSI