Origin and significance of the production of carbon dioxide during the ozonization of 13C-labeled D-glucose at different pH values

[1-C-13], [2-C-13] and [6-C-11] D-glucose were, respectively, ozonized in a semi-batch reactor in acidic and basic conditions. The composition of the gas phase was evaluated by on-line mass spectrometry measurements. The quantitative and isotopic analyses of the carbon dioxide formed during ozonization are presented and discussed. The data, correlated with previous literature results, clearly show that at pH 2.5 the production of carbon dioxide from C-6 and C-1 carbon atoms is nearly equivalent. Conversely, at higher pH values, CO, is released with a greater selectivity from the reducing end. The importance of the decarboxylation reaction in the formation of by-products with fewer than six carbon atoms is also demonstrated. (C) 2001 Elsevier Science Ltd. All rights reserved.