Exchange of 18O in the reaction of peroxynitrite with CO 2

Abstract

We have observed an exchange of 18O in the reactions of CO 2 with peroxynitrite using membrane-inlet mass spectrometry and HPLC negative electrospray ionization mass spectrometry. The exchange appeared on addition of peroxynitrite to a solution containing 18O-labeled CO 2 in equilibrium with bicarbonate. It was observed as a temporarily enhanced rate of depletion of 18O from CO 2, a rate that was greater than the rate of 18O depletion caused by the hydration/dehydration cycle of CO 2. In addition, we detected the appearance of mass peaks attributed to 18O in product NO 3 –.As a further measure of the 18O exchange, there was a redistribution of 18O such that the ratio of doubly to singly labeled CO 2 could not be described by the binomial expansion. This is not due to the hydration/dehydration cycle of CO 2 but most likely to recycling of CO 2 in the reaction with peroxynitrite. This 18O exchange associated with the reactions of CO 2 and peroxynitrite may open a new methodology for studying this significant process.