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
Here's How:
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.
Tips:
- 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).