How to Make Tris Buffer Solution for Medical or Lab Use

Buffer solutions are water-based liquids that include both a weak acid and its conjugate base. Because of their chemistry, buffer solutions can keep pH (acidity) at a nearly-constant level even when chemical changes are taking place. Buffer systems occur in nature, but they are also extremely useful in chemistry.

Uses for Buffer Solutions

In organic systems, natural buffer solutions keep pH at a consistent level, making it possible for biochemical reactions to occur without harming the organism. When biologists study biological processes, they must maintain the same consistent pH; to do so they used prepared buffer solutions. Buffer solutions were first described in 1966; many of the same buffers are used today.  

To be useful, biological buffers must meet several criteria. Specifically, they should be water soluble but not soluble in organic solvents. They should not be able to pass through cell membranes. In addition, they must be non-toxic, inert, and stable throughout any experiments for which they are used.

Buffer solutions occur naturally in blood plasma, which is why blood maintains a consistent pH between 7.35 and 7.45. Buffer solutions are also used in:

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• fermentation processes
• dying fabrics
• chemical analysis
• calibration of pH meters
• DNA extraction

What Is Tris Buffer Solution?

Tris is short for tris(hydroxymethyl) aminomethane, a chemical compound which is often used in saline because it is isotonic and non-toxic. Because it has a Tris has a pKa of 8.1 and a pH level between 7 and 9, Tris buffer solutions are also commonly used in a range of chemical analyses and procedures including DNA extraction. It is important to know that pH in tris buffer solution does change with the temperature of the solution.

How to Prepare Tris Buffer

It is easy to find commercially available tris buffer solution, but it is possible to make it yourself with the appropriate equipment.

Materials:

Calculate the amount of each item you need based on the molar concentration of the solution you want and the quantity of buffer you need.

• tris(hydroxymethyl) aminomethane 
• distilled deionized water
• HCl

Procedure:

1. Start by determining what concentration (molarity) and volume of Tris buffer you want to make. For example, Tris buffer solution used for saline varies from 10 to 100 mM. Once you have decided what you are making, calculate the number of moles of Tris that are required by multiplying the molar concentration of buffer by the volume of the buffer that is being made. (moles of Tris = mol/L x L)
2. Next, determine how many grams of Tris this is by multiplying the number of moles by the molecular weight of Tris (121.14 g/mol).  grams of Tris = (moles) x (121.14 g/mol)
3. Dissolve the Tris into the distilled deionized water, 1/3 to 1/2 of your desired final volume.
4. Mix in HCl (e.g., 1M HCl) until the pH meter gives you the desired pH for your Tris buffer solution.
5. Dilute the buffer with water to reach the desired final volume of solution.

Once the solution has been prepared, it can be stored for months in a sterile location at room temperature. Tris buffer solution's long shelf life is possible because the solution does not contain any proteins.