The invention provides a method of determining the impact of an agent on oxidation reactions of a nucleic acid species, said method comprising the steps of: - providing a reference sample containing a nucleic acid species; - providing a test sample containing the same nucleic acid species as the reference sample; - oxidizing the reference sample and the test sample by submitting each sample to identical electrochemical oxidation conditions; - on-line determining the oxidation profile of the electrochemically oxidized reference sample and of the electrochemically oxidized test sample using Electrospray Ionization-Mass Spectrometry (ESI-MS) or Matrix Assisted Laser Desorption Ionization-Mass Spectrometry (MALDI-MS); and - determining the impact of the agent on oxidation reactions of nucleic acid species by comparing the oxidation profiles of the reference sample and the test sample; wherein the agent is added to the test sample before the on-line determining of the oxidation profile. The present method is not only fast, but it is also extremely sensitive and it produces results that are highly predictive of the effect these same agents have on in vivo oxidation of nucleic acid species.