A method for the determination of organic hydroperoxides in a hydrocarbon which has been subjected to oxidative polymerization conditions is disclosed. The steps employed in the invention include mixing an organic cupric salt such as cupric acetate and a phenanthroline such as 2,9-dimethyl-1,10-phenanthroline with a sample of the hydrocarbon in an organic solvent such as acetonitrile, measuring the color change after a fixed period of time for cuprous complex formation, and comparing the measurement to the color change of a standard reference to determine the relative quantity of organic hydroperoxide in the sample.