HEPES is a zwitterionic organic buffer that is also used to maintain physiological pH of cell culture media. HEPES is recommended when the cell culture system is very sensitive, increasing the buffering capacity and stabilizing the pH within the range of 7.2 to 7.6, and is not dependent on CO2 levels.  

HEPES is widely used in many biochemical reactions and as a buffering agent in some cell culture media.  HEPES has no nutritional benefit to cells.  It is added to the media solely for extra buffering capacity when cell culture requires extended periods of manipulation outside of a CO2 incubator.

"Good buffers" such as HEPES are attributed with the following characteristics:

• pKa of HEPES is temperature dependent:
  At 25ºC: pKa= 7.48
  At 37ºC: pKa= 7.31

• High solubility

• Membrane impermeability

• Limited effect on biochemical reactions

• Very low visible and ultraviolet light absorbance

• Chemically and enzymatically stable

• Easy to prepare

Features

• Zwitterionic buffer 

• Liquid formulation with high solubility 

• Easy-to-use 1M solution

• Ideal for biochemistry, cell culture, and molecular biology applications