I am trying to make a 1M Tris Cl pH8 buffer with dry Tris base and Tris HCl. I know that it is possible to make Tris buffers without the use of HCl by combining powdered Tris acid with Tris base. How do I go about this? What is the formula I should use?
Dear Lizette,
To prepare 1 M Tris HCl, Dissolve 121.1 g of Tris base in 800 ml of H2O. Adjust the pH to the desired value by adding concentrated HCI. for pH 8 it is about 42 ml HCl. Allow the solution to cool to room temperature before making final adjustments to the pH.
Adjust the volume of the solution to 1 liter with H2O. Dispense into aliquots and sterilize by autoclaving.
I don't think you will be able to find accurate tables and/or formulas to calculate Tris/Tris-HCl ratios yielding a specific pH at such high concentrations. If you want to prepare lower concentration Tris/Tris HCl buffers, there are buffer charts on the net (one here, for instance: http://medicine.ucsf.edu/labs/brown/protocols_03_2005/sigma_buffer_chart.pdf but there are more), or you can use something like BufferMaker (http://www.chembuddy.com/?left=Buffer-Maker&right=buffer-calculator).
You should use the Henderson–Hasselbalch equation to determine the mole ratio of the base and conjugate acid. Then you can use simple algebra to figure out the actual amounts you need. You will need to determine the total number of moles of Tris by multiplying concentration in M by final volume in L. Assuming you want 1 liter, it will just be 1 mole. Then Tris base+Tris-HCl=1mol. And the Henderson–Hasselbalch equation is the second equation in your system of equations, so determining two variables with two equations will just be simple algebra.
https://www.aatbio.com/resources/buffer-preparations-and-recipes/trizma-buffer-ph-7-2-to-9-0
This website is amazing. The only thing is that the max molarity calculated is 0.1M. You can just multiply the amounts by 10 to make a 1M solution. I realize this question is 3 years old but I wanted to leave something for those coming after me who wanted answers to the same question that I had!
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