Ascorbate (L-Ascorbic acid or Vitamin C) is a six-carbon lactone that is synthesized from glucose in the liver of most mammalian species, but not by humans who must obtain ascorbate through dietary consumption. In humans, ascorbate serves as an antioxidant and acts as an electron donor for various enzymes. Cayman's Ascorbate Assay provides a reproducible, sensitive fluorescence-based tool for quantifying ascorbate from plasma, serum, urine, and fruit juices.