What is a buffer composed of?

A buffer is composed of a weak conjugate acid-base pair.  This means that the acid-base pair can either be a weak acid and its conjugate base, or a weak base and its conjugate acid. It is important to note that the weak conjugate acid-base pair helps ensure that the buffer effectively maintains a pH range. Buffers can be made several ways. Some examples of compounds that can function as buffers are listed in the bulleted points below.   

Acetic acid (weak organic acid, formula: CH3COOH) and a salt containing its conjugate base, the acetate anion (CH3COO)

Ammonia (weak base, formula: NH3) and a salt containing its conjugate acid, the ammonium cation, e.g., ammonium hydroxide (NH3OH)

Pyridine (weak base, formula: (C5H5NH+)) and a salt containing its conjugate acid, the ammonium cation, e.g., Ammonium Hydroxide (NH4OH)