Purity ≥99%. PIPES is a biological buffer (zwitterionic) designed by Good, et al., and typically referred to as Good's buffer useful in cell culture media formulations. Selection of biological buffer systems should include the following criteria: exclusion by biological membranes, low absorption between 240-700nm, chemically stable, and stable to temperature and concentration changes. PIPES has pKa (6.76 at 25°C) near the physiological pH which makes it useful in cell culture work. Solubility: Colorless, clear, complete Water (KF): ≤0.5% Absorbance (A280): ≤0.1 Absorbance (A260): ≤0.1 DNase: None Detected RNase: None Detected Protease: None Detected