Buffers

Buffers are solutions where the pH does not vary significantly when adding small amounts of an acid or a base, this is due to the common ion effect. Buffers are used to maintain a nearly constant pH, this is important as a change in pH may largely affect the outcome of an experiment, through processes such as denaturing proteins. The pH of a buffer can be calculated using the Henderson–Hasselbalch equation, shown in figure 1a. If you are dealing with a weak base, and only know the pK_b, then you first need to calculate pK_a with the following relationship shown in figure 1b. There is also a variation of the equation where you obtain pOH using pK_b, shown in equation 1c. Then to calculate the pH from pOH you can use the relationship shown in equation 1d.

Figure 1: 1a) Henderson–Hasselbalch equation. 1b) Equation to obtain pK_a from pK_b. 1c) Equation to obtain pOH from pK_b. 1d) Equation to obtain pH from pOH.

Buffers can be prepared using many different methods.