Some preventive cellulose antioxidants studied by an aromatic hydroxylation assay

Since the oxidative degradation of cellulose is enhanced in the presence of ferric compounds, the N,N '-(5-nitro,1,3-phenylene)-bisglutaramide hydroxy lation assay was used to test the efficiency of possible preventive antioxi dants: EDTA, DTPA, citrate, desferrioxamine methanesulphonate (desferal) an d phytate. The corresponding rate constants and apparent activation energie s for hydroxyl radical production in the aqueous systems in the pH interval 6.5-8 were obtained. The rate constants were correlated with the decrease of degree of polymerisation of artificially aged cellulose samples enriched with CaCO3 and iron in the form of the corresponding complex (R=0.9891). I t is concluded that the catalytic role of iron is similar in both systems a nd that the hydroxylation assay may provide valuable estimations of the deg radation rates of cellulosic materials in the conditions of use. The chelat ing compounds shown to have an antioxidant effect at 20 degreesC in the pH interval studied are DTPA, phytate, and desferal, in the order of increasin g positive effect. (C) 2001 Elsevier Science Ltd. All rights reserved.