Cayman's Nitrate/Nitrite Assay provides an accurate and convenient method for measurement of total nitrate/nitrite concentrations. This kit can be used to measure nitrate and nitrite in plasma/serum, urine, tissue culture media, and tissue homogenates. However, it cannot be used to analyze nitrate and nitrite from an in vitro assay of NOS in which excess NADPH has been added. For these assays a second method (LDH method) is utilized and is available from Cayman in a 96-well plate format (Item No. 760871).