What Is the Purpose of a Buffer in Chemistry?

A buffer is used to keep an aqueous solution within certain range of pH. The pH value depends on the concentration of ions H+ and OH-. The buffer is an aqueous mixture of an acid and its conjugated base. The acid reacts with OH- species (which raise the pH value) while the conjugated base reacts with H+ species (which lower the pH value). This allows the concentration of ions to remain unchanged.

In human blood

Our blood uses a carbonate buffer to maintain the pH of our blood between a narrow range of pH: 7.35 to 7.45.

Enzymatic Reactions

Enzymatic reactions (chemical reactions facilitated by an enzyme) occur only in certain range of pH. If the pH of the aqueous solution is not in the optimal range, then the enzyme is inactive or can even lose its proper conformation precipitate and come out of the solution.

Controlling Chemical Reactivity

Using different buffers, amines (R-NH2) can be protonated (R-NH3+) to make them soluble in water and deprotonated (by increasing the pH) so they can react as nucleophiles.

In Electrophoresis

Both DNA and protein electrophoresis relay on the negative charges carried by the DNA molecules or protein to separate these molecules in an electric field according to their size. Using the wrong pH (the wrong buffer) can cause inefficient separations due to uneven distribution of the negative charges.

In Dyes

Some dyes can change color depending on the pH of the solution. A specific buffer can be used to achieve the desired pH level in a dye. Some of these molecules are used to stain fabrics and some others are used as a detection tool to identify the pH of a solution based on its color.