Some preventive cellulose antioxidants studied by an aromatic hydroxylation assay

Abstract

Since the oxidative degradation of cellulose is enhanced in the presence of ferric compounds, the N,N′-(5-nitro,1,3-phenylene)bisglutaramide hydroxylation assay was used to test the efficiency of possible preventive antioxidants: EDTA, DTPA, citrate, desferrioxamine methanesulphonate (desferal) and phytate. The corresponding rate constants and apparent activation energies 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 CaCO 3 and iron in the form of the corresponding complex ( R=0.9891). It is concluded that the catalytic role of iron is similar in both systems and that the hydroxylation assay may provide valuable estimations of the degradation rates of cellulosic materials in the conditions of use. The chelating compounds shown to have an antioxidant effect at 20 °C in the pH interval studied are DTPA, phytate, and desferal, in the order of increasing positive effect.