Hydroxyl radical (•OH) is the most reactive oxygen species involved in many environmental and biological processes. The development of simple and reliable methods to quantitatively determine hydroxyl radicals is desired. Herein, a colorimetric strategy based on a modified Griess test has been presented. The detection started with the nitrite release from nitroimidazoles (nIm) upon its specific reaction with •OH radicals and subsequently nitrite quantification by Griess reagent. The result showed that this nitroimidazole modified Griess test (nIm-Griess) was successfully adapted for the measurement of •OH radicals generated by Fenton reaction, water radiolysis, as well as the activation of two antimalarials artemisinin (Art) and dihydroartemisinin (DHA). Copyright © 2018 Elsevier B.V. All rights reserved.