||Cobalt is a hard, lustrous, grey metal, a chemical element (symbol Co, atomic number 27 and atomic mass 58.9). Cobalt is an essential trace-element for all multicellular organisms as the active center of coenzymes called cobalamins. These include vitamin B-12 which is essential for plants and animals. Cobalt is also an active nutrient for bacteria, algae, and fungi, and may be a necessary nutrient for all life. Cobalt, particularly the Co+2 species, forms complexes with a large number of organic and inorganic molecules with a range of extinction coefficients in the visible range. The Cobalt Assay kit takes advantage of the reaction of Co+2 with mercaptoethanol in basic media. Under the condition, Cobalt forms a complex with a strong absorbance band at 475 nm. The metal ions Fe+2, Cu+2, Ni+2, Zn+2, Mn+2, exhibit less than 10% interference at this wavelength. The kit provides a quick simple accurate method of quantitating Co+2 in a variety of samples. The assay is linear in the range 3 to 50 nmol (0.18-3 µg) Cobalt, with a detection limit of ~ 3 nmol (or ~15 µM, 0.18 µg).