Flow Fix, 2% Paraformaldehyde Fixation Buffer is a sodium azide free buffer comprised of a neutral pH-buffered saline (i.e., Dulbecco's Phosphate-Buffered Saline) that contains 2% w/v paraformaldehyde. Sodium Azide –Free. Do not add sodium azide to buffers if you are concerned with recovering cell function.
Sodium azide inhibits metabolic activity and is kept separate to increase shelf life. After mixing and aliquoted, you may freeze. Thawed aliquots are stable at 40°C for up to two weeks. You may store frozen aliquots for up to five years. You may aliquot solution and sterilize them by autoclaving at 20 minutes, 121°C, liquid cycle, in order to store at room temperature.