Detection of photolytically produced hydroxyl radicals by reaction with 2,2,2-trichloroethanol

Abstract

A screening technique for the detection of the hydroxyl radical on photolysis of drugs or other chemicals is described. The technique depends upon scavenging the radical with 2,2,2-trichloroethanol in buffered aqueous solution and determining the liberated chloride ion. The system was validated using sodium nitrite as a model source of photolytically produced hydroxyl radicals. Competition kinetic experiments were performed using glucose, glycine and sulphate ion as competitive scavengers. The drugs metronidazole, phenylephrine and chloroquine diphosphate were examined for hydroxyl radical production on simulated sunlight photolysis, metronidazole caused no chloride liberation from 2,2,2-trichloroethanol on the time scale studied. In the case of chloroquine diphosphate, chloride ion liberated directly from the drug on its photolysis interfered with kinetic evaluation of the results. Chloride ion production from 2,2,2-trichloroethanol induced by phenylephrine was kinetically equivalent to that caused by the hydroxyl radical.