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Chemical structure of Tris - 2-Amino-2-hydroxymethyl-propane-1,3-diol

Tris is a common buffering agent and is short for tris[hydroxymethyl]aminomethane (C4H11NO3, 2-Amino-2-hydroxymethyl-propane-1,3-diol).

  • The formula weight is 121.14
  • The pKa of Tris is 8.3
  • dpKa/dT is -.028
  • A buffer at pH 6.8 at 25°C will have a pH of 6.46 at 37°C
    • Note that adding HCl during titration will affect the temperature of the solution
  • Dilution by a factor of 10 will reduce the pH by 0.1 pH units.

Preparing a 1M Tris, pH 7.4 solution, from biologicalworld

  • Weigh 121.1 g Tris in 700 ml double distilled water
  • Do not start with too much water; otherwise, the volume after pHing may be too great
  • Start stirring, and then check the pH
  • With a 3M HCl solution, start to pH the solution such that the pH reaches 7.4

(Be careful not to inhale the HCl.)

  • Add with double distilled water up to 1L
  • Filter or autoclave if necessary
  • May be better to store at 4 degrees C
  • Dilute to appropriate concentration for use in biochemistry or molecular biology experiments. 20 mM or 50 mM Tris, pH 7.4 solutions are common.


  • 18 months for Tris-HCl buffer according to this data sheet [1]
  • 2 years for Tris-EDTA according to this data sheet [2]

See also

  • TBS - tris-buffered saline
  • TBST - tris-buffered saline with Tween