Chelates find wide applications both in industry and laboratory where fixing of metal ions is required.

Standard EDTA solutions are widely used in volumetric analysis to determine the hardness of water. In this analysis EDTA complexes Ca²⁺ and Mg²⁺ ions which are responsible form hardness in water. Dimethlgloxime solution reacts with Ni²⁺ ions in ammoniacal medium and forms a red coloured precipitate of bis(dimethylglyoximato) nickel(II). Thus method is used for the quantitative estimation of Ni²⁺ ions. In volumetric analysis chelating agents are often used as indicators for the titration of some metal ions.

Hemoglobin imparts red colour to the human blood. It is a complex protein molecule, made up of simple heme molecules. Each heme group contains four nitrogen atoms which coordinate (Chelate formation to Fe⁺ ion. Hemoglobin picks up O₂ (form air which we breathe) and forms oxyhemoglobin in the lungs. Oxygen is released in the tissues, where it is needed for cell metabolism.

The green colouring matter present in plants which is called chlorophyll is a square planar chelate containing Mg²⁺ ions. This compound converts CO₂ and H₂O to starches and sugars in the plants and the necessary energy for this reaction is provided by the sun’s radiations.

Human beings have developed certain defense mechanisms form heavy metal ions such as Cd²⁺ , As³⁺, Hg²⁺ etc., which are highly poisonous. These metal ions are bound as chelated in our body by mucus metallothioneins, which are low molecular Wight proteins. These metal ions are thus inhibited form release into the organoisms.

The concentration of certain metal ions which may cause harmful effects in foods, drugs, cosmetics etc., are controlled by binding then as complex ions by the addition of chelating ligands. Poisoning by certain metals is also cured by binding them with chelate ligands. In case of poisoning by lead, the patient is given injections of CaNa₂ EDTA which form Pb-EDTA complex and in this form it is extracted form the body through the urine. Similarly, presence of free CI²⁺ ions in the liver (which cause central nervous disorders) are removed by giving penicillamine to the patient. It forms chelate complex with Cu²⁺ ions through O, N & S donors present in the same molecule.

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