How do you isolate fibrin from whole blood?

A plasma is part of whole blood. If you'll separate plasma from the whole blood, you'll see a yellow liquid component that's rich in protein.

blood (specilized bodily fluid used by the circulatory system to transfer oxygen and nutrients to an organism's cells) that has the attribute complete (with all constituent parts present)

The phrase 'whole blood' means blood that has not been modified except for the addition of an anticoagulant

no not really

The blood contains buffers like bicarbonate and phosphate buffers. The bicarbonate buffer is by far, the most important. For more on these buffers, look...