The ultimate goal of the filter sizing exercise is to quantify the effective filter area (EFA) needed to filter an entire
production batch over a set time frame. Such testing typically is done using a flat disc with a diameter of 47-mm. The proper
implementation of the flow decline method of assessing EFA requirements necessitates knowing the precise EFA of the model
filter, which can be measured using staining techniques.
A filter-sizing study using a 47-mm flat disc is intended as indicator trial, which is preliminary to a more meaningful verification
trial, or even to a more cogent assurance trial. The latter will require filter models characterized by a pleated membrane
design. The EFA assessment of the pleated filter models can be performed with confidence. This will result in dependable projections
of the EFA required for the batch processing filters.
Maik W. Jornitz is the group vice president of marketing & product management, filtration and fermentation technologies, and Wayne Garafola is an application specialist, both at Sartorius Stedim Biotech, Bohemia, NY, 631.870.8463, email@example.com
Theodore H. Meltzer is the principal at Capitola Consulting Co., Bethesda, MD.
1. Jornitz MW, Soelkner PG, Meltzer TH. Modern sterile filtration—the economics. PharmTech Eur. 2003;15(6)29–33.
2. Priebe PM, Jornitz MW, Meltzer TH. Making an informed membrane filter choice. BioProcess Int. 2003;1(10)64–6.
3. Parenteral Drug Association. Technical report 26: Liquid sterilizing filters. Bethesda, MD: PDA; 2008.
4. Meltzer TH, Jornitz MW. Pharmaceutical filtration—The management of organism removal. PDA, Bethesda, MD: PDA and River
Grove, IL: DHI Publishing LLC; 2006.
5. Jornitz MW, Meltzer TH. Comparing flow rates of microporous membranes. Eur J Parenteral Pharm Sci. 2009:14(1)19–23.
6. Jornitz MW, Meltzer TH. Filtration and purification in the biopharmaceutical industry. New York, NY: Informa; 2008
7. Jornitz MW, Meltzer TH, Bromm H, Priebe PM. Testing for the optimal filter membrane. Gen Eng News. 2004;24(13)50–51.
8. Jornitz MW, Meltzer TH, Bromm H, Priebe PM. Choosing the appropriate membrane filter—test requirements. PDA J Pharm Sci
Technol. 2005 Mar–Apr;59(2)96–101.
9. Jornitz MW. Filter construction and design. In: MW Jornitz, editor. Sterile Filtration. Berlin, Heidelberg: Springer Verlag;
2006. p. 105–124.