Cation-exchange capacity is measured by displacing all the bound cations with a concentrated solution of another cation, and then measuring either the displaced cations or the amount of added cation that is retained. Barium (Ba) and ammonium (NH) are frequently used as exchanger cations, although many other methods are available.
CEC measurements depend on pH, and therefore are often made with a buffer solution at a particular pH value. If this pH differs from the natural pH of the soil, the measurement will not reflect the true CEC under normal conditions. Such CEC measurements are called "potential CEC". Alternatively, measurement at the native soil pH is termed "effective CEC", which more closely reflects the real value, but can make direct comparison between soils more difficult.