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N-(2-hydroxyethyl)piperazine-N’-(2-ethanesulfonic acid); 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; CAS NUMBER: 7365-45-9

A Good buffer [1][2][3]. Stable pH vs. temperature, no primary amine groups, no metal chelation, near physiologic pH range.

  • pKa at 25C of 7.55 (7.31 at 37C)
  • a second pKa at pH 3 is not of interest
  • usable buffering range of 6.8 to 8.2
  • molecular weight 238.3
  • ΔpKa/ΔT = -.014
  • HEPES contains tertiary amines, which are reactive under certain conditions. See its structure in the Sigma catalog.
  • Chemical formula: C8H18N2O4S

Buffers are typically 1 M, prepared by neutralizing HEPES with sodium hydroxide. HEPES is essentially insoluble until it is neutralized.

  1. Good NE, Winget GD, Winter W, Connolly TN, Izawa S, and Singh RM. . pmid:5942950. PubMed HubMed [Good66]
  2. Good NE and Izawa S. . pmid:4206745. PubMed HubMed [Good74]
  3. Blanchard JS. . pmid:6717292. PubMed HubMed [Blanchard84]
All Medline abstracts: PubMed HubMed and
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