Ozone and hydroxyl radicals induced oxidation of glycine

The study of the oxidation of glycine by ozone and hydroxyl radicals has be en undertaken. Different experimental procedures involving the H2O2/UV proc ess or ozone in the presence of hydrogen peroxide on one hand, and ozone al one on the other hand allowed to distinguish between the two oxidation path ways. It has been shown that nitrites and nitrates are observed byproducts resulting from molecular ozonation whereas ammonium ions constitute the onl y inorganic nitrogen species from hydroxyl radicals induced decomposition o f glycine. Therefore, the ozonation process promoting radical pathways will favor ammonia production vs. nitrates. Among the organic compounds resulti ng from oxidation by hydroxyl radicals, oxalic acid was the major byproduct detected in the presence of oxygen. Oxamic acid and formic acid were also observed. In addition, the nitrogen mass balance indicated the formation of unidentified nitrogen byproducts derived from glycine, These nitrogen comp ounds could result from the interaction of oxygen with nitrogen radical, bu t, mainly, with a-amino radical of glycine. This reaction is very different from the molecular ozonation which directs the attack on the nitrogen func tional group before the C-N bond cleavage of the amino acid molecule. (C) 1 998 Elsevier Science Ltd. All rights reserved.