How To Make A Citrate Buffer

Citric acid is an organic acid commonly present in citrus fruits, but also in various animals and bacteria. A buffer consists of a combination of an acid along with its conjugate base or a base along with a conjugate acid. Buffer solutions help in maintaining the pH of the solution at a near constant value in numerous biochemical experiments. Citrate buffer is made by mixing citric acid along with its conjugate base, sodium citrate. The pH of a citrate buffer generally varies from 1.2 to 6.6.

Step 1

Calculate the quantity of citric acid and sodium citrate required for you to make the buffer by using an online "Citric acid buffer calculator." For example, a buffer with pH 4 requires 1.3g/liter of citric acid and 1.1g/liter of sodium citrate.

Step 2

Add the calculated amounts of sodium citrate and citric acid to 1 liter of water and stir it with a stirrer until both are fully dissolved.

Step 3

Use a pH meter to check the pH of the solution.

Step 4

Add a few drops of citric acid if the pH of the solution is higher than desired, or add a few drops of sodium citrate if it's lower than desired.