How to Prepare 1 M Tris-HCl Buffer (pH 8.0)

Introduction

Tris-HCl is a common buffer in molecular biology and biochemistry. It is used in protein, nucleic acid, electrophoresis, and enzyme workflows.

Tris, or tris(hydroxymethyl)aminomethane, is a weak base. Its useful buffering range is about pH 7.0–9.0. This makes it suitable for many laboratory solutions near neutral or mildly alkaline pH.

A 1 M Tris-HCl stock solution is convenient when preparing buffers at lower working concentrations.

Buffer Chemistry

Tris has a molecular weight of 121.14 g/mol. Its pKa is approximately 8.1 at room temperature. The exact pKa depends on temperature. A biological-buffer selection guide reports a temperature coefficient of approximately −0.029 pKa units per °C.

This temperature dependence matters during pH adjustment. A Tris solution adjusted at 4 °C will not have exactly the same pH when measured at room temperature.

For this reason, record the temperature when accurate pH control is important.

A 1 M Tris-HCl buffer is typically prepared by dissolving Tris base and adjusting the pH with hydrochloric acid (HCl). The final Tris concentration is determined by the amount of Tris base used.

Preparing 1 L of 1 M Tris-HCl, pH 8.0

For a final concentration of 1 M in 1 L:

Tris base required = 121.14 g

Component	Amount for 1 L
Tris base	121.14 g
HCl	Adjust pH to 8.0
Purified water	Bring final volume to 1 L

A practical procedure is:

Weigh 121.14 g of Tris base.
Add it to approximately 700–800 mL of purified water.
Stir until the Tris dissolves.
Measure the pH at the intended working or reference temperature.
Add HCl slowly while stirring until the solution reaches pH 8.0.
Bring the final volume to 1 L with purified water.
Mix thoroughly.

Do not treat the amount of HCl as a fixed recipe unless you are following a validated formulation. The amount required can vary with HCl concentration, temperature, and experimental conditions.

Thermo Fisher Scientific documents commercially prepared 1 M Tris solutions adjusted to pH 7.0 or 8.0 with HCl, confirming this general preparation approach.

For other volumes, use the ChemH Tris-HCl Buffer Calculator.

Practical Notes

Tris pH is temperature sensitive. If a protocol specifies a measurement temperature, adjust the buffer at that temperature when practical.

Add acid before bringing the solution to its final volume. Bringing the solution to 1 L first and then adding a substantial volume of acid changes the final volume and concentration.

Thermo Fisher lists autoclaving as compatible with its commercially prepared 1 M Tris solutions at pH 7.0 and 8.0. However, sterilization conditions should be evaluated based on the complete buffer composition and downstream application, especially when additional components are present.

The appropriate storage and sterilization method depends on the downstream application. Tris-containing solutions used for molecular biology workflows are commonly stored under conditions appropriate for maintaining stability and preventing contamination.