Potassium Phosphate Buffer (1 M, pH 6.5) Preparation and Recipe

Potassium phosphate buffers, sometimes called Gomori buffers, consist of a mixture of monobasic dihydrogen phosphate and dibasic monohydrogen phosphate. These buffers have excellent buffering capacity and are highly soluble in water. However, potassium phosphate buffer reacts with some metal ions including calcium and magnesium, and inhibits enzymatic reactions. Additionally, all phosphates precipitate in ethanol, which can be deleterious to some nucleic acid preparations that typically use ethanol solutions. Potassium phosphate buffer is used in research fields ranging from molecular biology to botany, due to its adaptability and affordability.

To prepare

L of Potassium Phosphate Buffer (1 M, pH 6.5):

Change the value in the textbox above to scale the recipe volume

Table 1. Required components

Component	Amount	Concentration
Potassium Phosphate Monobasic (mw: 136.09 g / mol)	#	#
Potassium phosphate dibasic (mw: 174.18 g / mol)	#	#

Prepare 800 mL of distilled water in a suitable container.
Add # of Potassium Phosphate Monobasic to the solution
Add # of Potassium phosphate dibasic to the solution
Adjust the pH to 6.5.
Add distilled water until the volume is 1 L.
Filter sterilize and store at room temperature.

References

This online resource may be cited as follows

MLA	"Quest Calculate™ Potassium Phosphate Buffer (1 M, pH 6.5) Preparation and Recipe." AAT Bioquest, Inc., 17 Oct. 2025, https://www.aatbio.com/resources/buffer-preparations-and-recipes/potassium-phosphate-buffer-1-m-ph-6-5.
APA	AAT Bioquest, Inc. (2025, October 17). Quest Calculate™ Potassium Phosphate Buffer (1 M, pH 6.5) Preparation and Recipe. AAT Bioquest. https://www.aatbio.com/resources/buffer-preparations-and-recipes/potassium-phosphate-buffer-1-m-ph-6-5.
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