Magnesium Assay Kit is a simple sensitive assay for quantitating magnesium in a variety of biological samples. The kit takes advantage of the specific requirement of glycerol kinase for Mg2+. An enzyme linked reaction leads to formation of an intensely colored (?max450nm) product whose formation is proportional to Mg2+ concentration. The linear range of the assay is 2-15 nmoles with detection sensitivity ~40 µM.