PIPES is a member of the ethanesulfonic acid buffer series, first introduced by Good et al., developed to meet certain criteria: midrange pKa, maximum water solubility and minimum solubility in all other solvents, minimal salt effects, minimal change in pKa with temperature, chemically and enzymatically stable, minimal absorption in visible or UV spectral range and easily synthesized. Since its pKa at 37 °C is near physiological pH, PIPES has applications in cell culture work.