Patent ID: 8652850

Claim:
A method of quantitatively determining 8-isoprostane, the method comprising: fluorescently labeling 8-isoprostane with a quinoxalinone derivative in an excess amount relative to amount by mole of 8-isoprostane, the quinoxalinone derivative which is represented by Formula (1) below wherein, in Formula (1), R 1 , R 2 , and R 3 are alkyl groups having 1 to 6 carbon atoms and n is an integer of 0 to 6; contacting a reaction mixture containing a fluorescently labeled 8-isoprostane and an unreacted quinoxalinone derivative with a cation exchange support having a sulfonic acid or a sulfonate immobilized thereon to separate the fluorescently labeled 8-isoprostane from the unreacted quinoxalinone derivative, and quantitatively determining the fluorescently labeled 8-isoprostane separated from the unreacted quinoxalinone derivative.