Tangential Flow Filtration is used to concentrate and diafilter the GFP product stream. We're going to pump a fluid through and across a special type of filter known as an ultrafiltration membrane. The size of the pores in the filter material determines what passes through and what's held back.
The solution that passes through the membrane is referred to as the permeate. Because the pores of the ultrafiltration membrane are small enough to keep the product from passing through, the permeate contains no product and is sent to waste. The portion of the feed stream that does not permeate the membrane is called the retentate. It contains the retained product and is the stream we are most interested in.
What makes TFF different is a core technology that enables it to be faster, more efficient, more flexible and even self-cleaning. In conventional filtration, a fluid is propelled directly into a filter. The particles within the stream that can't fit through the pores of the filter build up at the filter surface, eventually clogging it.
With TFF, the stream moves across the filter - that is, tangential to the filter - instead of directly at it. The cross-flow current actually picks material back out of the filter media or membrane and into the stream.
This retained material - called retentate - is recirculated to the supply tank and will continue to loop through the filter for as long as the process runs.