4-hydroxyethyl piperazine ethanesulfonic acid (HEPES) is an important hydrogen ion buffer, which has a good buffer capacity in the pH range of 6.8 ~ 8.2, and can control a constant pH for a long time. When the concentration is 10-50mmol /L, the general culture medium containing 20mmol/ L4-hydroxyethylpiperazine ethanesulfonic acid can have good buffering capacity and no toxic effect on cells
