Dipyridyl is an organic nitrogen compound formed from two linked pyridine rings, existing as isomers, valued as a chelating agent able to bind iron and other transition metals. Analytical chemists use it as a colorimetric reagent for iron determination in foods and biological materials, where the intense red complex enables sensitive quantification. By sequestering iron it also inhibits iron-catalysed oxidation reactions, a property exploited in studies of lipid oxidation and in formulations where trace metals threaten stability. Its metal-binding selectivity also makes it useful in research on iron-dependent enzymes in food systems.