Tris is a chemical with basic properties, having a pKa of 8.1. It can be used to buffer solutions from drastic pH changes, keeping them in the pH range of 7.0 to 9.0.
Make any Tris-HCl buffer in this pH range, at any molarity using these simple steps
Calculate Moles of Tris Base
Determine the number of moles of Tris base needed by multiplying the desired molar concentration of buffer by the volume of buffer being made.
mol/L * L = moles needed
Calculate Mass of Tris Base
Determine the mass of Tris base to weigh by multiplying the number of moles by the molecular weight (121.14 g/mol) of Tris.
moles needed * g/mol = g
Dissolve Tris Base in Water
Dissolve the required mass of Tris into a volume of deionized water approximately 1/3 of the desired volume of buffer to be made.
Adjust the pH
Using a pH meter, titrate the solution of Tris with 1M hydrochloric acid (HCl) until the correct pH is reached.
Bring to Volume
Add the TrisHCl mixture to a volumetric flask of the desired volume and add deionized water as required to complete the solution.
- Remember that pKa is not easily measured to an exact value. Slightly different pKa values might be available in the literature from different sources.
What You Need
- Standard labware: beakers, flasks, graduated cylinders, stirbars etc.
- pH meter and probe.
- Stirring hotplate.
- Tris base powder and hydrochloric acid (HCl).