EDTA, is a chelating agent with many applications in molecular biology. EDTA is often used in buffers as a metal ion inhibitor to maintain the stability and integrity of biological samples. EDTA binds to metal cations by forming a stable octahedral complex.

Water hardness can be measured using a procedure known as complexometric titration by adding a known concentration of the chelating agent EDTA through a burette to a sample containing an unknown amount of calcium and magnesium ions. EDTA reacts and captures these metal ions creating a larger metal complex.