phosphate buffer

Gomori buffers, the most commonly used phosphate buffers, consist of a mixture of monobasic dihydrogen phosphate and dibasic monohydrogen phosphate. By varying the amount of each salt, a range of buffers can be prepared that buffer well between pH 5.8 and pH 8.0 (please see the tables below). Phosphates have a very high buffering capacity and are highly soluble in water. However, they have a number of potential disadvantages:

• Phosphates inhibit many enzymatic reactions and procedures that are the foundation of molecular cloning, including cleavage of DNA by many restriction enzymes, ligation of DNA, and bacterial transformation.

• Because phosphates precipitate in ethanol, it is not possible to precipitate DNA and RNA from buffers that contain significant quantities of phosphate ions.

• Phosphates sequester divalent cations such as Ca²⁺ and Mg²⁺.

Preparation of 0.1 m Potassium Phosphate Buffer at 25°C

Preparation of 0.1 m Sodium Phosphate Buffer at 25°C